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Fakhruddin, Rakhmat. "Fluvial-Tidal to Fluvial-Lacustrine Sedimentation of the Middle Miocene to Pleistocene Mapia Formation, Dogiyai, Papua (Indonesia)." Sains Malaysiana 50, no. 7 (July 31, 2021): 1885–99. http://dx.doi.org/10.17576/jsm-2021-5007-05.
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A sedimentological and palynological investigation was carried out on outcropping sedimentary rocks at Dogiyai, Papua, proposed to be named as the Mapia Formation. The age range is from Middle Miocene to Pleistocene. The lower Mapia Formation was deposited at Metroxylon type to Nothofagus emarcida Zone, Middle Miocene to Early Pliocene. It is comprised of three facies associations: tidal channel, tidal point bar, and tidal flat deposits. A tidally dominated fluvially influenced depositional environment is suggested for the deposition of sediments of this unit. The upper Mapia Formation was deposited at Malvacipollis diversus Zone, Garcinia cuspidata type Zone, and Proteacidites sp. Zone, Late Pliocene to Pleistocene. It is comprised of five facies associations: delta front, slump, debrite, turbidite, and lacustrine mud deposits. A non-channelized deep-lacustrine slump and debris-flow dominated depositional environment is suggested for the deposition of sediments of this unit. The lower Mapia Formation was deposited as synorogenic clastic sediments at the beginning of Central Range orogeny event while the upper Mapia Formation was deposited in the piggyback basin at the major uplift event.
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Fambrini, Gelson Luís, Diego da Cunha Silvestre, José Acioli Bezerra de Menezes-Filho, Ian Cavalcanti da Costa, and Virgínio Henrique de Miranda Lopes Neumann. "Architectural and facies characterization of the Aptian fluvial Barbalha Formation, Araripe Basin, NE Brazil." Geological Society, London, Special Publications 488, no. 1 (2019): 119–50. http://dx.doi.org/10.1144/sp488-2017-275.
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AbstractThe Aptian Barbalha Formation records the beginning of the post-rift stage of the Araripe Basin. It consists predominantly of sandstones and mudstones interbedded with thin layers of bituminous black shales and conglomerates. The depositional and architectural features of the alluvial succession of the Barbalha Formation were characterized by detailed study and descriptions of the selected outcrops and analysis of well core data. In this study, two main depositional sequences were identified. The lower depositional sequence is more than 100 m thick and comprises a vertical facies succession composed of amalgamated, multistorey, braided fluvial channel sandstone bodies overlain by a widespread lacustrine black shale up to 10 m thick. The lacustrine black shales–carbonate mixed interval is known as the Batateira Beds and constitutes a regionally important stratigraphic correlation marker in the basin. This interval records the establishment of a large lake that experienced severe water-level fluctuations and anoxic events. The upper depositional sequence is 60–95 m thick, and mainly consists of thin, yellowish, medium- to fine-grained sandstones and variegated shales. The upper sequence rests unconformably on the lacustrine black shales of the Batateira Beds. Thin and discontinuous conglomerate beds at the base of the upper sequence laterally grade into coarse-grained sandstones. These coarse-grained sandstones are overlain by interbedded sandstones and mudstones organized in fluvial cycles. The upper and lower sequences of the Barbalha Formation are separated by an erosive unconformity, traceable throughout the study area, formed during a period of stratigraphic base-level lowering. This surface marks a change in the lower sequence from a dominantly fluvial depositional style, with amalgamated multistorey braided fluvial channel sand bodies, to a lacustrine system in the top to an eminently fluvial sedimentation, which in the basal section comprises amalgamated, multistorey, braided fluvial channel sand bodies, and in the superior section the amalgamated fluvial channels are overlain by floodplain and overbank sandstone bodies with fixed fluvial channel deposits, interpreted as a suspended-load-dominated fluvial system in the upper sequence. This change in the depositional style is accompanied by a reduction in grain size and a change in the fluvial regime, suggesting that the drainage system was restructured due to tectonic movements in the basin and climatic variations. In addition to the restructuring of the drainage basin, the characteristics of the discharge of the river system have changed, probably because of the more humid climatic conditions that dominated during the deposition of the upper sequence. The fluvial deposition in the lower sequence is associated with more ephemeral river systems, while the facies architecture of the upper sequence is associated with perennial systems and is suggestive of a suspended-load-dominated fluvial system. This fluvial system is capped by lacustrine deposits of the Crato Formation. The upper sequence grades upwards into the Crato Formation. The boundary between these two units is delineated by the presence of greenish calciferous shales that are covered by lacustrine laminated limestones and shales of Neoaptian age. Palaeocurrent readings from the fluvial deposits of both sequences display a consistent palaeoflow to the SE. Sedimentological and palaeontological evidence indicates a tectonic control on sedimentation and humid to subhumid climate conditions.
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Schöpfer, Kateřina, Roland Nádaskay, and Karel Martínek. "Evaluation of Climatic and Tectonic Imprints In Fluvial Successions of An Early Permian Depositional System (Asselian VrchlabÍ Formation, Krkonoše Piedmont Basin, Czech Republic)." Journal of Sedimentary Research 92, no. 3 (March 31, 2022): 275–303. http://dx.doi.org/10.2110/jsr.2020.137.
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ABSTRACT The Krkonoše Piedmont Basin, an early post-Variscan basin (c. 310–280 Ma) located in the NE Bohemian Massif (Czech Republic, central Europe), contains up to 300-m-thick non-marine Lower Permian (Asselian) deposits of the Vrchlabí Formation that crop out in its western part. The Early Permian Krkonoše Piedmont Basin exhibits striking similarities—in terms of tectonostratigraphic evolution, depositional patterns, and volcanism—to other early post-Variscan, near-equatorial intermontane basins. This work focuses on sedimentological analysis of the Vrchlabí Formation using outcrop data, combined with borehole and newly acquired field gamma spectrometry data. The formation consists predominantly of fluvial deposits in the southern part of the basin that pass laterally into deltaic and lacustrine deposits of the Rudník Member, located in the central part of the basin. Fluvial deposits are formed by sandstone and conglomeratic bodies, decimeters to several meters thick, interpreted as single-story and multi-story channel fills as well as various macroforms (e.g., bars) deposited by a low-sinuosity fluvial system. Channel fills intercalate with floodplain deposits centimeters to few meters thick. Vertically, the studied fluvial succession is divided into five intervals based on i) variable preservation ratio between channel fill and floodplain deposits and ii) external and internal geometries of sandstone and conglomerate channel bodies. In order to explain the observed vertical changes in fluvial style and to determine the main controlling factors, the interaction of the fluvial system with the contemporaneous lake was investigated by interpreting base-level changes of the fluvial system and their correlation with lake level changes. In the central part of the basin the transition from fluvio-deltaic to lacustrine deposits is represented by alternating beige to gray sandstones centimeters to few meters thick and by dark gray mudstones up to several meters thick that pass northwards into shales. At the outcrop scale, the new sedimentological data in combination with newly acquired gamma-ray logs enabled tracing the lateral extent of individual fluvial bodies. The integration of the new data with older borehole data leads to a substantially better understanding of lateral and vertical relationship between the fluvio-deltaic and the lacustrine facies at the basin scale. Tectonic subsidence played a substantial role during the initial deposition of the Vrchlabí Formation. However, the external geometries, the internal architecture of fluvial channel bodies, and the variable degree of floodplain preservation throughout the entire Vrchlabí Formation cannot be explained by tectonics only, but requires the consideration of climatic controls. The Early Permian fluvial system is interpreted to reflect seasonal discharge variability with dry and wet periods under long-term subhumid climatic conditions that shifted towards more arid conditions during the latest depositional stage of the Vrchlabí Formation.
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Buchheim, H. P., L. R. Brand, and H. T. Goodwin. "Lacustrine to fluvial floodplain deposition in the Eocene Bridger Formation." Palaeogeography, Palaeoclimatology, Palaeoecology 162, no. 1-2 (September 2000): 191–209. http://dx.doi.org/10.1016/s0031-0182(00)00112-7.
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Paudel, Mukunda Raj. "Facies analysis of Sunakothi Formation, Kathmandu basin, Nepal and its significance." Journal of Nepal Geological Society 47, no. 1 (June 30, 2014): 57–64. http://dx.doi.org/10.3126/jngs.v47i1.23105.
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This study decipher facies characteristic of Sunakothi Formation at southern part of Kathmandu Basin. Thick sandy and muddy sequence is found on an open lacustrine facies of the Kalimati Formation. Five facies associations have been recognized within the sandy and muddy facies. These are: (a) muddy rhythmites and silt and laminated to ripple sand bed of the prodeltaic origin (pd), (b) association of cross-stratification, rippledrift and parallel lamination in the lacustrine delta front origin (df), (c) muddy flood-plain and alteration of the fine and coarse sediments of delta-plain origin (dp), (d) sandy to silty rhythmites of the marginal shallow lacustrine origin above the delta-plain (ml), and (e) association of fluvial origin (fl ). Former three associations are interbeded by the thick gravel deposits, which is gravelly braided river origin. Transition from lacustrine to alluvial system is characterized by fluvial and deltaic system in the south. Sedimentology of the Sunakothi Formation indicates deposition during rapid lake level rise and also the thick channelized fluvial gravel beds within the sandy and muddy sequence indicate lake level fall. The cause could be climatic as well as activity of the basin margin tectonics. Sunakothi Formation is the southern counterpart of the Thimi-Gokarna Formations distributed in the northern part of the basin.
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OKUYUCU, CENGİZ, TATYANA K. DIMITROVA, MEHMET CEMAL GÖNCÜOĞLU, and İBRAHİM GEDİK. "Late Permian (Tatarian) fluvio-lacustrine successions in NW Anatolia (Zonguldak Terrane, Turkey): palaeogeographic implications." Geological Magazine 154, no. 5 (July 25, 2016): 1073–87. http://dx.doi.org/10.1017/s0016756816000674.
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AbstractLate Permian fluvio-lacustrine successions of the Çakraz Formation in the Zonguldak Terrane between the regions of Akçakoca and Ereğli were investigated in order to describe the litho- and biostratigraphic properties and explain the depositional environment. The studied succession with black, dark-grey to greenish-grey shales, siltstones and limestones is named the Alaplı Member to distinguish it from the classical red clastic successions, which are tentatively named the Ereğli Member of the Çakraz Formation. The organic-rich black shales, mudstones and limestones of the Alaplı Member yielded palynological assemblages suggesting a Lopingian (Tatarian) age. The lack of any marine macro- or microfossils, the fine-grained character of the lithofacies with abundant plant material and the association of poorly sorted conglomerates in the middle part of the succession indicate possible deposition in a broad range of fluvial and lacustrine environments. Successions of similar age and depositional environment are known from the East European Variscan Belt in Bulgaria and Romania. Common successions were also developed in actively extending shallow-marine platforms on the NW Palaeotethyan margin at the end of the Permian Period.
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Dietze, Elisabeth, Bernd Wünnemann, Kai Hartmann, Bernhard Diekmann, Huijun Jin, Georg Stauch, Sizhong Yang, and Frank Lehmkuhl. "Early to mid-Holocene lake high-stand sediments at Lake Donggi Cona, northeastern Tibetan Plateau, China." Quaternary Research 79, no. 3 (May 2013): 325–36. http://dx.doi.org/10.1016/j.yqres.2012.12.008.
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AbstractLake high-stand sediments are found in three onshore terraces at Lake Donggi Cona, northeastern Tibetan Plateau, and reveal characteristics of hydrological changes on lake shorelines triggered by climate change, geomorphological processes, and neo-tectonic movements. The terraces consist of fluvial–alluvial to littoral-lacustrine facies. End-member modeling of grain-size distributions allowed quantification of sediment transport processes and relative lake levels during times of deposition. Radiocarbon dating revealed higher than modern lake levels during the early and mid Holocene. Lake levels follow the trend of Asian monsoon dynamics, and are modified by local non-climatic drivers. Site-specific impacts explain fluctuations during the initial lake-level rise ~ 11 cal ka BP. Maximum lake extension reached ~ 9.2 cal ka BP, at ~ 16.5 m above present lake level (a.p.l.l.). Littoral and lacustrine sediment deposition paused during a phase of fluvial activity and post-depositional cryoturbations at ~ 8.5 cal ka BP, when the lake level fell to ~ 8 m a.p.l.l. After a second maximum at ~ 7.5 cal ka BP, lake level declined slightly at ~ 6.8 cal ka BP, probably due to a non-climatic pulse that caused lake opening. The level remained high until a transition towards drier conditions ~ 4.7 cal ka BP. Though discontinuous, high-stand sediments provide a unique, high-resolution archive.
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Kennedy, Kirsten, and Martin R. Gibling. "The Campbellton Formation, New Brunswick, Canada: paleoenvironments in an important Early Devonian terrestrial locality." Canadian Journal of Earth Sciences 48, no. 12 (December 2011): 1561–80. http://dx.doi.org/10.1139/e11-055.
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Strata of the Campbellton Formation, nearly 1 km-thick and known for its diverse fossil assemblage of early plants, arthropods, and fish, can be divided into six facies associations: (1) restricted lacustrine, (2) marginal lacustrine, (3) near-shore lacustrine, (4) coastal-deltaic, (5) sandy to gravelly alluvial plain, and (6) gravelly proximal alluvial environments. Lacustrine deposits with restricted circulation, due to depth or stagnation, are fine-grained with preserved organic material. The marginal lacustrine association consists of massive siltstone and very fine sandstone, interbedded with conglomerate. The latter are interpreted to have shed from older volcanic units forming the basin walls. The near-shore lacustrine association is characterized by rippled sandstone with microbialites. Alluvial strata include interbedded imbricate to nonimbricate conglomerate, trough cross-stratified sandstone, and barren to plant-bearing siltstone. Rare exposures of thickly bedded imbricate to weakly imbricated cobble–boulder conglomerate with sandy plant-bearing lenses are interpreted as products of hyperconcentrated debris flows. In the western belt, a braided-fluvial system had paleocurrents flowing WNW. Coastal-deltaic deposits west of the fluvial outcrops, containing aquatic vertebrates and invertebrates, had paleocurrents flowing ESE, suggesting a confined body of fresh or brackish water. In lower parts of the eastern belt, lacustrine facies are prevalent, representing a large open lake. Alluvial facies dominate upper parts of the formation, representing an eastward-flowing axial braided river system, with proximal alluvium shed transversely from the basin margins. Although most strata have a volcanic provenance, only one outcrop in the lacustrine beds shows evidence of active volcanism during deposition of the Campbellton Formation.
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Noll, C. A., and M. Hall. "FLUVIAL ARCHITECTURE AND THE TECTONIC CONTROL ON DEPOSITION OF ONSHORE EUMERALLA FORMATION, OTWAY RANGES, VICTORIA: IMPLICATIONS FOR EXPLORATION IN THE EARLY CRETACEOUS OTWAY BASIN." APPEA Journal 43, no. 1 (2003): 99. http://dx.doi.org/10.1071/aj02005.
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Spectacular outcrops of the terrestrial Aptian-Albian Eumeralla Formation are exposed in the Skenes Creek– Wongarra region, located on the eastern margin of the Otway Ranges, Victoria. The succession comprises mudstone-dominated floodplain and lacustrine successions and fluvially-derived sandstones. Lithofacies observed in the study area comprise intraformational and exotically derived conglomerate, massive and planar laminated sandstone, trough and tabular cross-bedded sandstone, ripple laminated sandstone, interbedded sandstone and mudstone, massive to laminated mudstone and thin coal seams. Architectural analysis of the fluvial system reveals these lithofacies are arranged into architectural elements that include channel elements, sandy bedforms, downstream and lateral accretion elements, laminated sand sheets and overbank fines elements.The fluvial system is characterised by low-sinuousity, braided river channels with high width to depth ratios. Palaeocurrent data indicates that the generally westward palaeoflow is interpreted to have been diverted into local axial-through drainage patterns by active northeast trending normal faults. One of these, the Skenes Creek Fault, is also likely to have structurally isolated floodplain and lacustrine successions from the main channel belt, leading to the deposition of an anomalously thick coal measure sequence in the hanging wall of the fault. The local study therefore provides insight into regional lithofacies and potential source rock distributions, and the associated tectonostratigraphic evolution of the Eumeralla Formation in the eastern Otway Basin. While the nature of the Eumeralla Formation sandstone does not lend itself to good reservoir properties, the geometry and internal structure of the sands provide an excellent model for other fluvial sandstone reservoir reconstructions.
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Ginat, Hanan, Ezra Zilberman, and Idit Saragusti. "Early pleistocene lake deposits and Lower Paleolithic finds in Nahal (wadi) Zihor, Southern Negev desert, Israel." Quaternary Research 59, no. 3 (May 2003): 445–58. http://dx.doi.org/10.1016/s0033-5894(03)00029-2.
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AbstractAn Early Pleistocene fluvio-lacustrine sequence from the extremely arid southern Negev desert, Israel, indicates that climatic conditions during that period were humid enough to support the formation of a lake (Lake Zihor) there. The lacustrine sediments were deposited in a tectonic valley that developed along the Zihor tectonic line after the deposition of the Pliocene Arava Formation. They intercalate with fluvial sediments that contain several horizons of reddish calcic paleosols. The lacustrine sequence comprises three sedimentary cycles. Each starts with a dark clay layer overlain by a white limestone unit, both of which contain abundant freshwater fauna, and terminates with a green detrital limestone that contains only one type of brackish-water ostracod. The top of each green limestone unit is characterized by pedogenic features and microrelief, indicating desiccation of the lake and soil development. Isotope data support the hypothesis that the white limestone was deposited in an open, freshwater lake. The incision of the present channel of Nahal (wadi) Zihor in the lacustrine sediments is manifested by a series of rock-cut and fluvial terraces (Q1–Q4) capped by gypsic-salic soils, which reflect the onset of the present, extremely arid climate. Over 100 find-spots and larger occurrences of prehistoric artifacts assigned to the Lower Paleolithic were discovered near Lake Zihor. On the basis of techno-typological and stratigraphic considerations, these assemblages are divided into two groups, the first of which may be contemporaneous with the lake, while the second is found mainly on the younger Q1 and Q2 terraces. It is estimated that the lake existed for more than 100,000 years. The climate during this period was probably semiarid, but water budget calculations suggest that, in addition to surface runoff, seepage of groundwater along the Zihor Line contributed a considerable amount of water to the lake.
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Woolfe, Ken J. "Devonian depositional environments in the Darwin Mountains: Marine or non-marine?" Antarctic Science 5, no. 2 (June 1993): 211–20. http://dx.doi.org/10.1017/s0954102093000276.
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The depositional environment of the Devonian Taylor Group has been subject to considerable debate for over 30 years. The debate stems largely from a belief that the abundant and diverse trace fossils represent a marine ichnofauna, whereas sedimentary features, including palaeosols, desiccation polygons and red beds, are more typical of a non-marine setting. The debate is reconciled by a reinterpretation of the trace fossil assemblage which shows that the trace fossils comprise a typical fresh water (Scoyenia ichnofacies) assemblage, and their occurrence in the Taylor Group in the Darwin Glacier area is entirely consistent with deposition in a mixed fluvial-lacustrine-subaerial environment.
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PENNOCK, D. J., and W. J. VREEKEN. "INFLUENCE OF SITE TOPOGRAPHY ON PALEOSOL FORMATION IN THE HIGHWOOD RIVER BASIN, SOUTHERN ALBERTA." Canadian Journal of Soil Science 66, no. 4 (November 1, 1986): 673–88. http://dx.doi.org/10.4141/cjss86-067.
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Soil stratigraphical and pedological techniques were used to examine the evolution of paleosols in the Highwood River Basin of southern Alberta. The paleosols were located on three types of glacial deposits: glacio-lacustrine, glacio-fluvial, and diamicton. Before the deposition of Mazama tephra at 6600 year B.P. (prior to 6600 years B.P.) episodic colluviation occurred on sloping sites, with paleosols forming during depositional hiatuses. Level surfaces were stable, allowing formation of thick, well-developed paleosols. Eolian deposition occurred on all surfaces during the last 6600 yr. The morphological and analytical characteristics of the paleosols differ depending on the influence of topography on the geomorphic processes occurring at the site. The variability in paleosols in this area limits the type of paleoenvironment information which can be inferred from paleosols. Key words: Holocene soil, paleosol, soil genesis, landscape position, soil geomorphology
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Sztanó, Orsolya, Michal Kováč, Imre Magyar, Michal Šujan, László Fodor, András Uhrin, Samuel Rybár, Gábor Csillag, and Lilla Tőkés. "Late Miocene sedimentary record of the Danube/Kisalföld Basin: interregional correlation of depositional systems, stratigraphy and structural evolution." Geologica Carpathica 67, no. 6 (December 1, 2016): 525–42. http://dx.doi.org/10.1515/geoca-2016-0033.
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AbstractThe Danube / Kisalföld Basin is the north-western sub-basin of the Pannonian Basin System. The lithostratigraphic subdivision of the several-km-thick Upper Miocene to Pliocene sedimentary succession related to Lake Pannon has been developed independently in Slovakia and Hungary. A study of the sedimentary formations across the entire basin led us to claim that these formations are identical or similar between the two basin parts to such an extent that their correlation is indeed a matter of nomenclature only. Nemčiňany corresponds to the Kálla Formation, representing locally derived coarse clastics along the basin margins (11- 9.5 Ma). The deep lacustrine sediments are collectively designated the Ivanka Formation in Slovakia, while in Hungary they are subdivided into Szák (fine-grained transgressive deposits above basement highs, 10.5 - 8.9 Ma), Endrőd (deep lacustrine marls, 11.6 -10 Ma), Szolnok (turbidites, 10.5 - 9.2 Ma) and Algyő Formations (fine-grained slope deposits, 10 - 9 Ma). The Beladice Formation represents shallow lacustrine deltaic deposits, fully corresponding to Újfalu (10.5 - 8.7 Ma). The overlying fluvial deposits are the Volkovce and Zagyva Formations (10 - 6 Ma). The synoptic description and characterization of these sediments offer a basin-wide insight into the development of the basin during the Late Miocene. The turbidite systems, the slope, the overlying deltaic and fluvial systems are all genetically related and are coeval at any time slice after the regression of Lake Pannon initiated about 10 Ma ago. All these formations get younger towards the S, SE as the progradation of the shelf-slope went on. The basin got filled up to lake level by 8.7 Ma, since then fluvial deposition dominated.
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Guo, Fengtao, and Peter McCabe. "Lithofacies analysis and sequence stratigraphy of the Roseneath-Epsilon-Murteree gas plays in the Cooper Basin, South Australia." APPEA Journal 57, no. 2 (2017): 749. http://dx.doi.org/10.1071/aj16202.
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The early–middle Permian Roseneath-Epsilon-Murteree (REM) strata of the Cooper Basin, South Australia, has conventional and unconventional gas plays. To better understand the sedimentary evolution of the strata, eight key cored wells for the REM in the South Australia were selected and more than 1400 m cores have been characterised to study the lithofacies, facies associations and associated stacking patterns. Twelve lithofacies are identified and further categorised into eight facies associations: (1) open lacustrine, (2) lacustrine shoreface, (3) flood plain/interdistributary bay/channel fill, (4) fluvial channel/distributary channel, (5) crevasse channel/splay/natural levee, (6) distributary mouth bar, (7) prodelta, and (8) mire/swamp. Cyclic stacking patterns are distinguished both in cores and well logs. X-ray diffraction analysis indicates the lower and middle parts of the Murteree Shale mainly consist of claystone and are characteristic of deep water sediments. The upper Murteree Shale has a larger percentage of silt and sand, which suggests an overall regressive process. The Epsilon Formation displays three stages of deposition: (1) a lower, thin, upward-coarsening package of beach and lacustrine shoreline deposits with a continued regression from the underlying Murteree Shale; (2) a coaly, middle unit deposited by distributary channels, crevasse splays, mires and delta mouth bars; and (3) an upper unit of cyclic coarsening-upward claystone, siltstone and sandstone, deposited in shoreline environments with fluvial modifications. The Roseneath Shale resulted from transgression after deposition of the upper Epsilon Formation with a relatively rapid rise of lake level marked by transgressive lags. A final coarsening-upward sequence of shoreline deposits indicates an ending phase of regression.
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Rogala, Becky, Philip W. Fralick, Larry M. Heaman, and Riku Metsaranta. "Lithostratigraphy and chemostratigraphy of the Mesoproterozoic Sibley Group, northwestern Ontario, Canada." Canadian Journal of Earth Sciences 44, no. 8 (August 1, 2007): 1131–49. http://dx.doi.org/10.1139/e07-027.
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The 950 m thick Sibley Group is a relatively flat-lying assemblage of siliciclastic and chemical sedimentary rocks exposed from the northwest shore of Lake Superior to the Lake Nipigon region of Ontario. Remnants of the Sibley Group occur in an ovoid area that sagged at ~1.5 Ga, creating accommodation space for braided fluvial sediments, derived as either first or multicycle detritus from the Trans-Hudson Orogen. This was followed by a transgressive episode and deposition of lacustrine siliciclastics and evaporites. An influx of sediment from the south occurred immediately prior to final contraction of the lacustrine system and deposition of strandline, stromatolite-bearing carbonates. The change in paleoslope was accompanied by development of a north–south-oriented half-graben. Overlying subaerial deposits represent deposition on a sabkha or saline mud flat. This assemblage is abruptly succeeded upward by flooding of the basin and major deltaic progradation and capped by a delta-top fluvial system with extensive preservation of floodplain deposits. The majority of the deltaic sediment was derived from Proterozoic sources to the south. An unconformity separates this assemblage from a thick succession of sandstone deposited as an aeolian dune field, with detritus probably coming from as far as the New Quebec Orogen to Baltica region. The geochemistry of medium-grained sandstone denotes that sediment became more mature and quartz-rich upsection and that the source areas evolved to more felsic and less alkalic compositions. Paleomagnetically correlated units in the Belt Supergroup, Apache Group, and Troy Quartzite in western North America indicate that the broad climatic fluctuations recorded in the Sibley Group may represent continent-wide events.
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Khuong, Hung The, and Tra Thuy Thi Lai. "Studies on lithofacies sequences in the Hoanh Bo basin, Quang Ninh province by using Markov chain model and Entropy function." Journal of Mining and Earth Sciences 63, no. 1 (February 28, 2022): 15–26. http://dx.doi.org/10.46326/jmes.2022.63(1).02.
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The succession of lithofacies in the Dong Ho and Tieu Giao formation's Hoanh Bo basin was statistically analyzed using the modified Markov chain model and the function of Entropy. Based on the field definitions, petrographic investigation, and their borehole logs, the lithofacies study was carried out to determine the sediment deposition system and the deposition environment. Seventeen sub - lithofacies organized within the succession are recognized in three lithofacies associations. The analysis result of the Markov chain and chi-square or X2 test indicates that the deposition of the lithofacies is a non - markovian process and represents cyclic deposition of asymmetric fining - upward. To evaluate the randomness of the occurrence of lithofacies in a succession, entropy analysis was performed. Each state is associated with two types of entropy; one is relevant to the Markov matrix expressing upward transitions (entropy after deposition) and the other is relevant to the downward transition matrix (entropy before deposition). The energy regime calculated from the maximum randomness entropy analysis indicates that changing patterns in a deposition has resulted from rapid to steady flow. This results in a change in the depositional pattern from alluvial - fluvial to lacustrine environments, specifically from conglomerate facies (A1) → sandstone facies (A2)→ fine-grained and non - debris facies (A3).
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Helmens, Karin F., Rene W. Barendregt, Randolph J. Enkin, Judith Baker, and Paul A. M. Andriessen. "Magnetic Polarity and Fission-Track Chronology of a Late Pliocene–Pleistocene Paleoclimatic Proxy Record in the Tropical Andes." Quaternary Research 48, no. 1 (July 1997): 15–28. http://dx.doi.org/10.1006/qres.1997.1886.
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Two sections exposing a Late Pliocene–Pleistocene sedimentary sequence in the marginal valleys of the Bogotá Basin (Colombian Andes, South America) were sampled for paleomagnetic analysis. Magnetostratigraphy and fission-track dates of tephra beds provide a detailed geochronologic calibration for the sedimentary basin. Measurements of magnetic susceptibility complement the regional environmental record provided by lithological and palynological evidence. Sedimentation in the Bogota Basin started in the early part of the Gauss Chron at ca. 3.2 myr. The oldest recorded sediments belong to the Guasca Member of the Upper Tilatá Formation. They were deposited in a lacustrine/paludal environment, near the end of the tectonic uplift in the Bogotá area, and/or under Pliocene climatic conditions that were warmer than today. Repeated climate cooling associated with glaciations in the surrounding mountains resulted in the deposition of a fluvial–lacustrine complex referred to as the Subachoque Formation. The first glaciation is placed near the Gauss/Matuyama polarity reversal at 2.6 myr. A lithologic change in the Subachoque Formation marked by coarser-grained fluvial deposits and a possible increase in amplitude of the magnetic susceptibility signal occurs near the Matuyama/Brunhes boundary at 0.8 myr, indicating a shift toward higher magnitude climate oscillations.
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Souza, Pamela, Gelson Fambrini, Renan Queiroz, and Leonardo Oliveira. "GEOLOGIA DA ÁREA NORDESTE DA FOLHA POÇO DA CRUZ, BACIA DE JATOBÁ, NORDESTE DO BRASIL." Estudos Geológicos 30, no. 1 (December 17, 2020): 45–78. http://dx.doi.org/10.18190/1980-8208/estudosgeologicos.v30n1p45-78.
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The Jatobá Basin is located in the south-central portion of Pernambuco state and northern Bahia and Alagoas, it has an area of approximately 5000 km² in a NE-SW preferred direction and sedimentary record has approximately 3 km. It is a rift basin developed under extensional tectonic events related to the rupture of the Gondwana supercontinent and it marks the northern limit of the aborted Recôncavo-Tucano-Jatobá rift system. The stratigraphic succession in the Campos district, Ibimirim (PE), comprises the Syneclise sequence and Rift Initiation sequence as well as part of the Rift Climax sequence of the basin. Using columnar sections and identifying sedimentary facies, six stratigraphic units were recognized, in addition to the quaternary coverage. The two lower fluvial-marine units are related to the siluro-devonian sedimentary records of the Syneclise sequence,while fluvial-eolic and lacustrine sediments of the upper units mark the Rift Initiation and Rift Climax sequences. The Aliança Formation, discussed in a particular way in this paper, represents the first sedimentary records of the beginning of the Neojurassic rift (Dom João stage). Since it was deposited in a lacustrine system, this formation has highly fossiliferous decimetric carbonate levels arranged in thick pelitic packages, suggesting deposition during times of energy variations within a shallow lake. The detailing of the stratigraphy of these deposits, associated with petrographic and paleontological studies, brings a new understanding of the depositional system that occurred in this environment and the first processes that started the opening of the rift during the Upper Jurassic.
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Shao, Hong Jun. "Petroleum Geological Characteristics of South Buir Sag in Tamsag Basin, Mongolia." Advanced Materials Research 347-353 (October 2011): 1609–14. http://dx.doi.org/10.4028/www.scientific.net/amr.347-353.1609.
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South Buir Sag is located in Tamsag Basin of Mongolia, which is a Mesozoic faulted basin. South Buir Sag shows the distinct characterization of faulted structure: many uplifts and many depressions, depressions alternated with many uplifts. This special structure framework results in the characteristic of multi-provenances, multi-depocencers. South Buir Sag experienced the whole process of Cretaceous basin development. South Buir Sag formed fan deltas-lacustrine system in the period of Tsagaantsav Formation, Lower Zuunbayan Formation which occurred in rifting stage. It developed deltas-lacustrine system during the period of Upper Zuunbayan Formation，Sainshand Formation，Bayanshire Formation which is in rifting-downwarping stage. From the period of Bayanshire Formation to present, South Buir Sag underwent downwarped and developed fluvial system. The sandstone of fan deltas front can provide favorable reservoir for hydrocarbon accumulation. Some regions of structure and deposition matching well can form lithology-structure petroleum reservoir.
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Gilbert, Robert, and John Shaw. "Glacial and early postglacial lacustrine environment of a portion of northeastern Lake Ontario." Canadian Journal of Earth Sciences 29, no. 1 (January 1, 1992): 63–75. http://dx.doi.org/10.1139/e92-008.
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A deep channel in bedrock extending to more than 25 m below sea level occurs along the north shore of the otherwise uniformly shallow Kingston basin of Lake Ontario. Bathymetric and subbottom acoustic data are used to map the topography of the channel and to reconstruct its late glacial and postglacial sedimentary history. The results are interpreted as showing that the large channel and smaller channels nearby were created by high-velocity subglacial meltwater flow. Acoustic facies assemblages of sediments deposited in the channels record patchy deposition, or deposition followed by partial erosion, of glacial sediments on the bedrock of the channel floor, followed by deposition and episodic erosion of glaciolacustrine sediment in a high-energy, ice-proximal lake. Palaeoslope analysis confirms that the early Holocene low-water phase of Lake Ontario resulted in the development of a fluvial system in part of the channel. Water level was controlled by a sill at Kingston. Kingston basin, the Bay of Quinte, and possibly, for a short time, a much larger area of the upper Great Lakes drained through the channel. However, for most of the period, until it was flooded by the rising waters of Lake Ontario, the channel was occupied by a small river on a wide floodplain or it was flanked by broad marshes.
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Larena, Z., C. Arenas, J. I. Baceta, X. Murelaga, and O. Suarez-Hernando. "Stratigraphy and sedimentology of distal-alluvial and lacustrine deposits of the western-central Ebro Basin (NE Iberia) reflecting the onset of the middle Miocene Climatic Optimum." Geologica Acta 18 (May 20, 2020): 1–26. http://dx.doi.org/10.1344/geologicaacta2020.18.7.
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Stratigraphic and sedimentological study of distal alluvial and lacustrine deposits in the Plana de la Negra-Sancho Abarca area (western-central Ebro Basin, NE Iberia) within the early and middle Miocene allows five main lithofacies to be characterized and mapped within two tectosedimentary units, construction of a sedimentary facies model and discussion on allogenic controls on sedimentation. In this area, the boundary between tectosedimentary units T5 and T6 appears to be conformable and is marked by the change from dominant clastics to carbonates. Correlation of the studied outcrops with nearby sections that already had magnetostratigraphic and biostratigraphic data allows the studied succession to be dated from C5Dr to C5Cn (Burdigalian-Langhian), placing the boundary T5/T6 at ca. 16.1-16.05Ma. Seven vertical facies sequences document deposition of distal alluvial clastics and palustrine and lacustrine carbonates. Sandstones and mudstones represent low-sinuosity channels and lateral and terminal splays by unconfined flows runnig across the alluvial plain, associated to the Pyrenean-derived Luna fluvial system. The carbonates contain charophytes, ostracods, bivalves and gastropods, indicating deposition in 2-4m deep lakes. Laminated carbonate facies record reworking of shore carbonates and the influx fine-siliciclastic sediment offshore. Abundant bioturbation and desiccation features indicate episodic submergence and subaerial exposure. Four main episodes of alluvial and associated palustrine/lacustrine facies belt shifts are identified. Alluvial deposition in the studied T5 unit is related to low lake level conditions, rather than to a Pyrenean uplift. The maximum extent of the freshwater carbonates occur at the base of unit T6. This is consistent with conditions of increasing humidity of the Middle Miocene Climatic Optimum.
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Clemmensen, Lars B., Dennis W. Kent, Malte Mau, Octávio Mateus, and Jesper Milàn. "Triassic lithostratigraphy of the Jameson Land Basin (central East Greenland), with emphasis on the new Fleming Fjord Group." Bulletin of the Geological Society of Denmark 68 (June 5, 2020): 95–132. http://dx.doi.org/10.37570/bgsd-2020-68-05-rev.
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The lithostratigraphy of the Triassic deposits of the Jameson Land Basin in central East Greenland is revised. The new Scoresby Land Supergroup is now composed of the Wordie Creek, Pingo Dal, Gipsdalen and Fleming Fjord Groups. This paper only deals with the lithostratigraphy of the late Early-Late Triassic continental deposits of the latter three groups with emphasis on the vertebratebearing Fleming Fjord Group. The new Pingo Dal Group consists of three new formations, the Rødstaken, Paradigmabjerg and Klitdal Formations (all elevated from members), the new Gipsdalen Group consists of three new formations, the Kolledalen, Solfaldsdal (with the new Gråklint Member) and Kap Seaforth Formations (all elevated from members), and the new Fleming Fjord Group is subdivided into three new formations, the Edderfugledal, Malmros Klint and Ørsted Dal Formations (all elevated from members). The Edderfugledal Formation contains two cyclic bedded, lacustrine members, a lowermost Sporfjeld Member (elevated from beds), and an uppermost Pingel Dal Member (elevated from beds). The lacustrine red beds of the Malmros Klint Formation are not subdivided. The lacustrine and fluvial Ørsted Dal Formation contains three new members. In the eastern and central part of the basin, the formation is initiated by cyclic bedded, red lacustrine mudstones of the Carlsberg Fjord Member (elevated from beds), while in the northwestern part of the basin the lowermost part of the formation is composed of grey fluvial conglomerates and sandstones with subordinate red mudstones of the Bjergkronerne Member (elevated from beds). The uppermost part of the formations in most of the basin is composed of cyclic bedded, variegated lacustrine mudstones and grey to yellowish marlstones of the Tait Bjerg Member (elevated from beds). The sediments in the Fleming Fjord Group contain remains of a rich and diverse vertebrate fauna including dinosaurs, amphibians, turtles, aeotosaurs, pterosaurs, phytosaurs and mammaliaforms. Most vertebrate bones have been found in uppermost Malmros Klint Formation, and in the Carlsberg Fjord and Tait Bjerg Members. The Norian–early Rhaetian, lacustrine Fleming Fjord Group was deposited at about 41° N on the northern part of the supercontinent Pangaea. Lacustrine sedimentation was controlled by seasonal as well as longer-term (orbital) variation in precipitation. Precipitation was probably brought to the basin by southwesterly winds. The lacustrine sediments of the uppermost Fleming Fjord Group show deposition during increasingly humid conditions changing the lake environment from an ephemeral lake-steppe area to a perennial lake. This evolution of lake environment suggests a change from a winter-wet temperate climate to one with precipitation throughout the year.
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Clemmensen, Lars B., Dennis W. Kent, Malte Mau, Octávio Mateus, and Jesper Milàn. "Triassic lithostratigraphy of the Jameson Land Basin (central East Greenland), with emphasis on the new Fleming Fjord Group." Bulletin of the Geological Society of Denmark 68 (June 5, 2020): 95–132. http://dx.doi.org/10.37570/bgsd-2020-68-05.
Full textAbstract:
The lithostratigraphy of the Triassic deposits of the Jameson Land Basin in central East Greenland is revised. The new Scoresby Land Supergroup is now composed of the Wordie Creek, Pingo Dal, Gipsdalen and Fleming Fjord Groups. This paper only deals with the lithostratigraphy of the late Early-Late Triassic continental deposits of the latter three groups with emphasis on the vertebratebearing Fleming Fjord Group. The new Pingo Dal Group consists of three new formations, the Rødstaken, Paradigmabjerg and Klitdal Formations (all elevated from members), the new Gipsdalen Group consists of three new formations, the Kolledalen, Solfaldsdal (with the new Gråklint Member) and Kap Seaforth Formations (all elevated from members), and the new Fleming Fjord Group is subdivided into three new formations, the Edderfugledal, Malmros Klint and Ørsted Dal Formations (all elevated from members). The Edderfugledal Formation contains two cyclic bedded, lacustrine members, a lowermost Sporfjeld Member (elevated from beds), and an uppermost Pingel Dal Member (elevated from beds). The lacustrine red beds of the Malmros Klint Formation are not subdivided. The lacustrine and fluvial Ørsted Dal Formation contains three new members. In the eastern and central part of the basin, the formation is initiated by cyclic bedded, red lacustrine mudstones of the Carlsberg Fjord Member (elevated from beds), while in the northwestern part of the basin the lowermost part of the formation is composed of grey fluvial conglomerates and sandstones with subordinate red mudstones of the Bjergkronerne Member (elevated from beds). The uppermost part of the formations in most of the basin is composed of cyclic bedded, variegated lacustrine mudstones and grey to yellowish marlstones of the Tait Bjerg Member (elevated from beds). The sediments in the Fleming Fjord Group contain remains of a rich and diverse vertebrate fauna including dinosaurs, amphibians, turtles, aeotosaurs, pterosaurs, phytosaurs and mammaliaforms. Most vertebrate bones have been found in uppermost Malmros Klint Formation, and in the Carlsberg Fjord and Tait Bjerg Members. The Norian–early Rhaetian, lacustrine Fleming Fjord Group was deposited at about 41° N on the northern part of the supercontinent Pangaea. Lacustrine sedimentation was controlled by seasonal as well as longer-term (orbital) variation in precipitation. Precipitation was probably brought to the basin by southwesterly winds. The lacustrine sediments of the uppermost Fleming Fjord Group show deposition during increasingly humid conditions changing the lake environment from an ephemeral lake-steppe area to a perennial lake. This evolution of lake environment suggests a change from a winter-wet temperate climate to one with precipitation throughout the year.
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Rainbird, R. H., and J. A. Donaldson. "Nonglaciogenic deltaic deposits in the early Proterozoic Gowganda Formation, Cobalt Basin, Ontario." Canadian Journal of Earth Sciences 25, no. 5 (May 1, 1988): 710–24. http://dx.doi.org/10.1139/e88-067.
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The Gowganda Formation in the eastern part of the Cobalt Basin comprises the Coleman Member and the conformably overlying Firstbrook Member. The Firstbrook Member differs from the Coleman Member in that its lithofacies display (i) marked lateral continuity, (ii) abundant diagenetic red colouration, (iii) evidence of tidal deposition, and (iv) a lack of glaciogenic features. The Firstbrook Member is here divided into a mud-dominated lower facies, a silt-dominated middle facies, and sand-dominated upper facies. These are respectively equated with the prodelta, delta slope, and delta foreslope subenvironments of a prograding river-dominated deltaic wedge composed of coalescing deltas (probably braid deltas). The deltaic wedge was likely fed by a fluvial system analogous to the braidplain system that prevailed during deposition of the overlying Lorrain Formation. Uninterrupted delta progradation is suggested by a single coarsening-upward sequence up to 535 m thick. Deposition probably occurred within a marine rather than lacustrine basin.
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Ambrose, G., M. Scardigno, and A. J. Hill. "PETROLEUM GEOLOGY OF MIDDLE–LATE TRIASSIC AND EARLY JURASSIC SEQUENCES IN THE SIMPSON BASIN AND NORTHERN EROMANGA BASIN OF CENTRAL AUSTRALIA." APPEA Journal 47, no. 1 (2007): 127. http://dx.doi.org/10.1071/aj06007.
Full textAbstract:
Prospective Middle–Late Triassic and Early Jurassic petroleum systems are widespread in central Australia where they have only been sparsely explored. These systems are important targets in the Simpson/Eromanga basins (Poolowanna Trough and surrounds), but the petroleum systems also extend into the northern and eastern Cooper Basin.Regional deposition of Early–Middle Triassic red-beds, which provide regional seal to the Permian petroleum system, are variously named the Walkandi Formation in the Simpson Basin, and the Arrabury Formation in the northern and eastern Cooper Basin. A pervasive, transgressive lacustrine sequence (Middle–Late Triassic Peera Peera Formation) disconformably overlies the red-beds and can be correlated over a distance of 500 km from the Poolowanna Trough into western Queensland, thus providing the key to unravelling Triassic stratigraphic architecture in the region. The equivalent sequence in the northern Cooper Basin is the Tinchoo Formation. These correlations allow considerable simplification of Triassic stratigraphy in this region, and demonstrate the wide lateral extent of lacustrine source rocks that also provide regional seal. Sheet-like, fluvial-alluvial sands at the base of the Peera Peera/Tinchoo sequence are prime reservoir targets and have produced oil at James–1, with widespread hydrocarbon shows occurring elsewhere including Poolowanna–1, Colson–1, Walkandi–1, Potiron–1 and Mackillop–1.The Early Jurassic Poolowanna Formation disconformably overlies the Peera Peera Formation and can be subdivided into two transgressive, fluvial-lacustrine cycles, which formed on a regional scale in response to distal sea level oscillations. Early Jurassic stratigraphic architecture in the Poolowanna Trough is defined by a lacustrine shale capping the basal transgressive cycle (Cycle 1). This shale partitions the Early Jurassic aquifer in some areas and significant hydrocarbon shows and oil recoveries are largely restricted to sandstones below this seal. Structural closure into the depositional edge of Cycle 1 is an important oil play.The Poolowanna and Peera Peera formations, which have produced minor oil and gas/condensate on test respectively in Poolowanna–1, include lacustrine source rocks with distinct coal maceral compositions. Significantly, the oil-bearing Early Jurassic sequence in Cuttapirrie–1 in the Cooper Basin correlates directly with the Cycle–1 oil pool in Poolowanna–1. Basin modelling in the latter indicates hydrocarbon expulsion occurred in the late Cretaceous (90–100 Ma) with migration into a subtle Jurassic age closure. Robust Miocene structural reactivation breached the trap leaving only minor remnants of water-washed oil. Other large Miocene structures, bound by reverse faults and some reflecting major inversion, have failed to encounter commercial hydrocarbons. Future exploration should target subtle Triassic to Jurassic–Early Cretaceous age structural and combination stratigraphic traps largely free of younger fault dislocation.
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Tuomisto, Hanna, Kalle Ruokolainen, and Jukka Salo. "LAGO AMAZONAS: FACT OR FANCY?" Acta Amazonica 22, no. 3 (September 1992): 353–61. http://dx.doi.org/10.1590/1809-43921992223361.
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It has been suggested that a huge lake, Lago Amazonas, covered a large part of the Amazon basin until as recently as two thousand years ago. According to this hypothesis, the topmost sediments in western Amazonia are almost universally young deposite of lacustrine and deltaic origin. The hypothesis has gained some attention among biologists because of its implications for biological phenomena in Amazonia, especially biogeography and biodiversity. According to the available geological data, however, Amazonia is geologically far more complex than assumed by the lake hypothesis. In the following discussion we will point out the weaknesses of the Lago Amazonas hypothesis, and indicate alternative explanations of the surface geology that are based on tectonically controlled fluvial deposition.
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Zhu, Xiaomin, Shunli Li, Jiawang Ge, Dakang Zhong, Qin Zhang, and Defa Ge. "Paleogene sequence framework and depositional systems in the Sunda and Asri Basins, Indonesia." Interpretation 6, no. 2 (May 1, 2018): T377—T391. http://dx.doi.org/10.1190/int-2017-0121.1.
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Based on seismic reflection characteristics, lithologic associations, and basin structure evolution stages, the Banuwati Formation, Zelda and Gita Members in the Oligocene could be divided into six third-order sequences. The new sequence framework has been established in the Sunda and Asri Basins. Sequence relationship between wells and seismic data has been implemented in the basin scale through the use of synthetical seismic records of 14 wells. Depositional systems, such as delta, fan-delta, nearshore subaqueous fan, and fluvial, are identified in the Banuwati Formation, Zelda and Gita Members. Alluvial fan, subaqueous fan, and fan delta occurred on the steep slopes of the basins. Deltas were mainly developed on the gentle slopes of the basins. There were three separated small basins with fluvial and shore-shallow lake deposition in the Banuwati Formation (SQ1). During the Lower Zelda (SQ2) sedimentation, the former separated small basins enlarged in a certain extent where delta and subaqueous fan were developed. Major lacustrine facies under deepwater environments and deltaic facies developed in the Upper-Lower Zelda and Middle-Upper Zelda (SQ3, SQ4). The sedimentary situation was almost the same as the Middle Zelda, but the water depth became shallower during Upper Zelda sedimentation. Later, fluvial and swamp developed in the upper part of the Upper Zelda and Gita Member (SQ5, SQ6). In general, basin sedimentary evolution is consistent with tectonic evolution. Finally, the favorable sandstone distribution in the Banuwati and Mid-Upper Zelda Member for further exploration was predicted according to the depositional systems, slope break, and present hydrocarbon occurrence. Three fields or eight favorable plays should be paid attention to for further exploration in the Sunda and Asri Basins, Indonesia.
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Sharpe, David R., and W. R. Cowan. "Moraine formation in northwestern Ontario: product of subglacial fluvial and glaciolacustrine sedimentation." Canadian Journal of Earth Sciences 27, no. 11 (November 1, 1990): 1478–86. http://dx.doi.org/10.1139/e90-157.
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Long, arcuate, stratified end moraines in northwestern Ontario may represent major and rapid sedimentation events in glacial Lake Agassiz. Rapid lowering of the lake or lift of a marginal ice dam may have triggered widespread outbursts of subglacial meltwater which deposited these end moraines as coalesced or broad subaqueous lacustrine fans. Moraine cores are of undeformed gravel, sand, and silty sand that fine upward. Coarse beds are massive to weakly stratified. Large-scale cross-stratification may be present. Sandy rhythmic beds are laterally transitional to silt–clay rhythmites (varves). Similar facies occur in adjoining eskers.Moraine sediments have the expected characteristics of rapid deposition on subaqueous fans and, therefore, may not represent either prolonged sedimentation or stable ice margins. Rather, they may reflect rapid sedimentation associated with large discharges that induced transient instability in the drainage network and (or) surging prior to marginal sedimentation. This explanation for moraine formation questions the traditional view that large end moraines represent climatically controlled stillstands.
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Zhang, H. C., Q. Z. Ming, G. L. Lei, W. X. Zhang, H. F. Fan, F. Q. Chang, B. Wünnemann, and K. Hartmann. "Dilemma of Dating on Lacustrine Deposits in an Hyperarid Inland Basin of NW China." Radiocarbon 48, no. 2 (2006): 219–26. http://dx.doi.org/10.1017/s0033822200066418.
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Conventional and accelerator mass spectrometry (AMS) radiocarbon, TL, OSL, and IRSL dating results on samples from the cores D100 and I70 from Ejina Basin, one of the most important inland basins in arid-hyperarid NW China, show that it is difficult to determine the ages of sediments at different depths. AMS ages of core D100 samples demonstrate that the sediments at depths from 10 to 90 m were formed between 14 to 30 kyr BP. The inverted ages from both the D100 and I70 cores imply that there was a strong reworking of the sediments during and after deposition processes. The inverted ages also indicate drastic fluctuations of groundwater bearing soluble organic matters, which might be related to neotectonic activities and climate changes during the period. Consequently, it is impossible to establish an accurate and reliable chronology for the cores based only on these dates. All AMS ages, if they are reliable and acceptable, indicate a high deposition rate (5∼8 mm/yr), and since all TL, OSL, and IRSL ages are much older than those given by AMS, it makes these methods questionable for determining the ages of lacustrine-fluvial-alluvial deposits.
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Bala, Emilia. "Textural features of the beach sediments of Wast Water Lake, Northwest England." Miscellanea Geographica 20, no. 2 (June 1, 2016): 46–53. http://dx.doi.org/10.1515/mgrsd-2016-0013.
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Abstract This study is dedicated to Wast Water Lake (Northwest England, Great Britain) and the character of its beach sediments. The aim of the study is to identify the textural features of the lake’s beach sediments based on two methods. The first is a granulometric analysis and the second a pebble shape analysis according to Zingg (1935) and Sneed & Folk (1958). Both analyses were carried out for all of the lake’s accessible beaches and the cliffs adjacent to them. The transport and deposition history of the examined sediments was identified through field research and laboratory analysis. The results show that the textural features of the sediments at Wast Water are more often typical of a fluvial environment, rather than having been changed by lacustrine water movements.
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Gall, Ryan, Justin Birdwell, Riley Brinkerhoff, and Michael Vanden Berg. "Geologic characterization and depositional history of the Uteland Butte Member, Green River Formation, southwestern Uinta Basin, Utah." Geosites 50 (September 1, 2022): 1–26. http://dx.doi.org/10.31711/ugap.v50i.106.
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The 15- to 65-m-thick informal Uteland Butte member of the Eocene Green River Formation represents the first widespread transgression of Lake Uinta in the Uinta Basin, Utah. This study assesses the spatial and temporal variation of Uteland Butte member deposits along a 40-km transect in the southwestern margin of the Uinta Basin using detailed measured sections, organic and inorganic geochemical data, and outcrop gamma ray logs. Fourteen lithofacies are identified, which comprise seven facies associations linked to with lacustrine, palustrine, and deltaic depositional settings. Facies associations are traceable laterally across the study area, where five 4- to 12-m-thick depositional cycles are identified. Each shallowing upwards cycle is defined by a >1.5-m-thick basal package of organic-rich, argillaceous laminated mudstone, and is capped by thick packages of bedded carbonate. In the far western study area (Kyune Creek Canyon), thick deposits of organic-rich mudstone are present and represent the most distal outcrop section; time-equivalent strata in the eastern study area (Minnie Maud Creek Canyon) are relatively organic lean with higher silt and clay content, interpreted to represent proximal lake margin deposits influenced by a nearby delta. The outcrop belt is correlated to more distal cores and well logs across the western Uinta Basin. Similar lithological and petrophysical patterns across the western Uinta Basin are used to subdivide stratigraphy into nine laterally contiguous sub-units based on nomenclature from the oil-producing area of the central basin (from base to top: lower Uteland Butte, D Bench, D Shale, C Bench, C Shale, B Bench, B Shale, A Bench, and A Shale). Siliciclastic clay-rich and carbonaterich intervals are correlated across the region and indicate distinct siliciclastic- and carbonate-dominated lake phases during Uteland Butte member deposition. Climate is interpreted to be the dominant driver of these claycarbonate cycles, in which relatively humid periods resulted in increased fluvially derived siliciclastic sediment into the basin (clay-rich periods), and arid periods resulted in evaporative conditions with decreased fluvial sediment input that favor carbonate accumulation. Climatically driven depositional cycles within the Uteland Butte member reflect, to a smaller degree, the larger scale climatically driven depositional cycles observed at the member- and formation levels of Paleocene and Eocene Uinta Basin stratigraphy. Importantly, the Uteland Butte member clay-carbonate cycles showcase how relatively small-scale climate shifts can impact basin-scale lacustrine deposition.
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Dietze, E., F. Maussion, M. Ahlborn, B. Diekmann, K. Hartmann, K. Henkel, T. Kasper, G. Lockot, S. Opitz, and T. Haberzettl. "Sediment transport processes across the Tibetan Plateau inferred from robust grain-size end members in lake sediments." Climate of the Past 10, no. 1 (January 16, 2014): 91–106. http://dx.doi.org/10.5194/cp-10-91-2014.
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Abstract. Grain-size distributions offer powerful proxies of past environmental conditions that are related to sediment sorting processes. However, they are often of multimodal character because sediments can get mixed during deposition. To facilitate the use of grain size as palaeoenvironmental proxy, this study aims to distinguish the main detrital processes that contribute to lacustrine sedimentation across the Tibetan Plateau using grain-size end-member modelling analysis. Between three and five robust grain-size end-member subpopulations were distinguished at different sites from similarly–likely end-member model runs. Their main modes were grouped and linked to common sediment transport and depositional processes that can be associated with contemporary Tibetan climate (precipitation patterns and lake ice phenology, gridded wind and shear stress data from the High Asia Reanalysis) and local catchment configurations. The coarse sands and clays with grain-size modes >250 μm and <2 μm were probably transported by fluvial processes. Aeolian sands (~200 μm) and coarse local dust (~60 μm), transported by saltation and in near-surface suspension clouds, are probably related to occasional westerly storms in winter and spring. Coarse regional dust with modes ~25 μm may derive from near-by sources that keep in longer term suspension. The continuous background dust is differentiated into two robust end members (modes: 5–10 and 2–5 μm) that may represent different sources, wind directions and/or sediment trapping dynamics from long-range, upper-level westerly and episodic northerly wind transport. According to this study grain-size end members of only fluvial origin contribute small amounts to mean Tibetan lake sedimentation (19± 5%), whereas local to regional aeolian transport and background dust deposition dominate the clastic sedimentation in Tibetan lakes (contributions: 42 ± 14% and 51 ± 11%). However, fluvial and alluvial reworking of aeolian material from nearby slopes during summer seems to limit end-member interpretation and should be crosschecked with other proxy information. If not considered as a stand-alone proxy, a high transferability to other regions and sediment archives allows helpful reconstructions of past sedimentation history.
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Dietze, E., F. Maussion, M. Ahlborn, B. Diekmann, K. Hartmann, K. Henkel, T. Kasper, G. Lockot, S. Opitz, and T. Haberzettl. "Sediment transport processes across the Tibetan Plateau inferred from robust grain size end-members in lake sediments." Climate of the Past Discussions 9, no. 4 (August 21, 2013): 4855–92. http://dx.doi.org/10.5194/cpd-9-4855-2013.
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Abstract. Grain size distributions offer powerful proxies of past environmental conditions that are related to sediment sorting processes. However, they are often of multimodal character because sediments can get mixed during deposition. To facilitate the use of grain size as palaeoenvironmental proxy this study aims to distinguish the main detrital processes that contribute to lacustrine sedimentation across the Tibetan Plateau using grain size end-member modelling analysis. Between three and five robust grain size end-member subpopulations were distinguished at different sites from similarly-likely end-member model runs. Their main modes were grouped and linked to sediment transport and depositional processes associated with certain climatic background and catchment configurations. The coarse sands and clays with grain size modes > 250 μm and < 2 μm were probably transported by fluvial processes. Aeolian sands (~ 200 μm) and coarse local dust (~ 60 μm), transported by saltation and in near-surface suspension clouds, are probably related to occasional westerly storms in winter and spring. Coarse regional dust with modes ~ 25 μm may derive from near-by sources that keep in longer-term suspension. The continuous background dust is differentiated into two robust end-members (modes: 5–10 and 2–5 μm) that may represent different sources, wind directions and/or sediment trapping dynamics from long-range, upper-level westerly and episodic northerly wind transport. According to this study grain size end-members of only fluvial origin contribute small amounts to mean Tibetan lake sedimentation (19 ± 5%), whereas local to regional aeolian transport and background dust deposition dominate the clastic sedimentation in Tibetan lakes (contributions: 42 ± 14% and 51 ± 11%). However, fluvial and alluvial reworking of aeolian material from nearby slopes during summer seems to limit end-member interpretation and should be crosschecked with other proxy information. If not considered as a stand-alone proxy, a high transferability to other regions and sediment archives allows helpful reconstructions of past sedimentation history.
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Pfeifer, Lily S., Gerilyn S. Soreghan, Stéphane Pochat, and Jean Van Den Driessche. "Loess in eastern equatorial Pangea archives a dusty atmosphere and possible upland glaciation." GSA Bulletin 133, no. 1-2 (June 19, 2020): 379–92. http://dx.doi.org/10.1130/b35590.1.
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Abstract Carboniferous–Permian strata in basins within the Central Pangean Mountains in France archive regional paleoequatorial climate during a unique interval in geological history (Pangea assembly, ice-age collapse, megamonsoon inception). The voluminous (∼1.5 km) succession of exclusively fine-grained red beds that comprises the Permian Salagou Formation (Lodève Basin, France) has long been interpreted to record either lacustrine or fluvial deposition, primarily based on a local emphasis of subaqueous features in the upper ∼25% of the section. In contrast, data presented here indicate that the lower-middle Salagou Formation is dominated by up to 15-m-thick beds of internally massive red mudstone with abundant pedogenic features (microscale) and no evidence of channeling. Up-section, limited occurrences of ripple and hummocky cross-stratification, and mudcracks record the intermittent influence of shallow water, but with no channeling nor units with grain sizes exceeding coarse silt. These data suggest that the most parsimonious interpretation for the Salagou Formation involves eolian transport of the sediment and ultimate deposition as loess in shallow, ephemeral lacustrine environments. Provenance analyses of the Salagou Formation indicate coarse-grained protoliths and, together with geochemical proxies (chemical index of alteration [CIA] and τNa) that correspond respectively to a low degree of chemical weathering and a mean annual temperature of ∼4 °C, suggest that silt generation in this case is most consistent with cold-weathering (glacial and associated periglacial) processes in the Variscan highlands. Together with previous studies that detailed voluminous Permian loess in western equatorial Pangea, this work shows a globally unique distribution of dust at low latitudes that can be linked either directly to glaciated alpine terranes or to reworked and deflated deposits of other types (e.g., fluvial outwash) where fine-grained material was originally generated from glacial grinding in alpine systems. These results further support a revised model for early Permian climate, in which extratropical ice sheets coexisted with a semiarid tropics that may have hosted significant ice at moderate elevation.
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DITCHFIELD, P. W., E. WHITFIELD, T. VINCENT, T. PLUMMER, D. BRAUN, A. DEINO, F. HERTEL, J. S. OLIVER, J. LOUYS, and L. C. BISHOP. "Geochronology and physical context of Oldowan site formation at Kanjera South, Kenya." Geological Magazine 156, no. 07 (September 12, 2018): 1190–200. http://dx.doi.org/10.1017/s0016756818000602.
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AbstractOldowan sites in primary geological context are rare in the archaeological record. Here we describe the depositional environment of Oldowan occurrences at Kanjera South, Kenya, based on field descriptions and granulometric analysis. Excavations have recovered a large Oldowan artefact sample as well as the oldest substantial sample of archaeological fauna. The deposits at Kanjera South consist of 30 m of fluvial, colluvial and lacustrine sediments. Magneto- and biostratigraphy indicate the Kanjera South Member of the Kanjera Formation was deposited during 2.3–1.92 Ma, with 2.0 Ma being a likely age for the archaeological occurrences. Oldowan artefacts and associated fauna were deposited in the colluvial and alluvial silts and sands of beds KS1–3, in the margins of a lake basin. Field descriptions and granulometric analysis of the sediment fine fraction indicate that sediments from within the main archaeological horizon were emplaced as a combination of tractional and hyperconcentrated flows with limited evidence of debris-flow deposition. This style of deposition is unlikely to significantly erode or disturb the underlying surface, and therefore promotes preservation of surface archaeological accumulations. Hominins were repeatedly attracted to the site locale, and rapid sedimentation, minimal bone weathering and an absence of bone or artefact rounding further indicate that fossils and artefacts were quickly buried.
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Kar, S. K., Surendra Prasad, and Gopendra Kumar. "Quaternary sediments of Indo-Gangetic, Brahmaputra and adjoining inland basins and the problem of demarcation of Pleistocene-Holocene Boundary." Journal of Palaeosciences 46, no. (1-2) (December 31, 1997): 196–210. http://dx.doi.org/10.54991/jop.1997.1340.
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The Quaternary sediments deposited in the Indo-Gangetic, Brahmaputra and adjoining smaller inland basins and Duns formed after the Middle Pleistocene Himalayan Orogenic Movement (HOM-4), are fluvial-fluviolacustrine and or lacustrine in nature. A synthesis of the available data in the Brahmaputra Basin and its comparison with that of the Indo-Gangetic Basin and Duns suggests two cycles of sedimentation, separated by a period of erosion and non-deposition and continuous in inland basins, such as Bhimtal-Naukuchia Tal, Hawalbagh in Kumaun region in Uttar Pradesh and Loktak Lake in Manipur. The sediments of the first cycle which terminated in late Upper Pleistocene are, in general, oxidised and referred to as the Older Alluvium, while that of the second assigned to Holocene, is unoxidised grey in color and constitutes the Newer Alluvium.
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Metaxas, A., D. E. Karageorgiou, G. Varvarousis, Th Kotis, M. Ploumidis, and G. Papanikolaou. "GEOLOGICAL EVOLUTION - STRATIGRAPHY OF FLORINA, PTOLEMAIDA, KOZANI AND SARADAPORO GRABEN." Bulletin of the Geological Society of Greece 40, no. 1 (June 8, 2018): 161. http://dx.doi.org/10.12681/bgsg.16502.
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The purpose of this research is to comprehend the geological and stratigraphical evolution of Fiorina, Ptolemaida, Kozani and Sarandaporo graben. This graben extends North of the Greek borders and is more than 150 Km long. The activity of big and profound faults ofNW-SE direction, in NW Macedonia, after the end of the Alpine orogenesis cycle and during the Early Miocene was related to the formations ' deposition. A large number of samples were collected from drill cores for the examination of palynology, paleoflora, fossils, and diatoms in order to determine the formations ' sequence and age. The basement and the borders of the depression, belong to the Pelagonian geotectonic zone. The deposition of the Early Neogene 's series is following. During the Late Pliocene the previous series, is developing into a lacustrine-marshland system, resulting to the deposition of Late Neogene's series formations. In the Quartenary the following formations are deposited: Proastion formation, Perdika formation, terrestrial, fluvial-terrestrial formation, recent formation. Four (4) phases of lignitogenesis have been specified, mainly in the Ptolemaida - Amynteo basin. In this graben they have been deposited the most important lignite deposits of Greece.
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Owen, R. B., R. W. Renaut, R. Potts, and A. K. Behrensmeyer. "Geochemical trends through time and lateral variability of diatom floras in the Pleistocene Olorgesailie Formation, southern Kenya Rift Valley." Quaternary Research 76, no. 1 (July 2011): 167–79. http://dx.doi.org/10.1016/j.yqres.2011.05.002.
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AbstractThe Olorgesailie Formation (1.2–0.49 Ma) consists of fluvial and lacustrine rift sediments that have yielded abundant Acheulean artifacts and a fossil hominin (Homo cf. erectus). In testing prior understandings of the paleoenvironmental context, we define nine new geochemical zones. A Chemical Index of Alteration suggests increased catchment weathering during deposition of Members 1, 2, 7, 11, and 13. Biophile elements (Br, S) peak in M8–9 and lower M13 possibly reflecting increased input from soil erosion. REE data show that the Magadi Trachytes supplied most siliciclastic grains. Sixteen diatom stages indicate conductivities of 200–16,000 μS cm− 1 and pH of 7.5–9.5 for five deep-water lakes, ten shallow lakes and sixteen wetlands. These results are compared with diatom data from other sections in the basin and show aquatic spatial variability over km-scale distances. Similar floras are traceable over several kilometers for M2, M3 and M9, indicating broadly homogeneous lacustrine conditions during these times, but diatoms in other members imply variable conditions, some related to local tectonic controls. This lateral and temporal variability emphasizes the importance of carrying out stratigraphic sampling at multiple sites within a basin in efforts to define the environmental context relevant to human evolution.
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Michelsen, Olaf, Lars H. Nielsen, Peter N. Johannessen, Jan Andsbjerg, and Finn Surlyk. "Jurassic lithostratigraphy and stratigraphic development onshore and offshore Denmark." Geological Survey of Denmark and Greenland (GEUS) Bulletin 1 (October 28, 2003): 145–216. http://dx.doi.org/10.34194/geusb.v1.4651.
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A complete updated and revised lithostratigraphic scheme for the Jurassic succession of the onshore and offshore Danish areas is presented together with an overview of the geological evolution. The lithostratigraphies of Bornholm, the Danish Basin and the Danish Central Graben are described in ascending order, and a number of new units are defined. On Bornholm, the Lower–Middle Jurassic coal-bearing clays and sands that overlie the Lower Pliensbachian Hasle Formation are referred to the new Sorthat Formation (Lower Jurassic) and the revised Bagå Formation (Middle Jurassic). In the southern Danish Central Graben, the Middle Jurassic succession formerly referred to the Lower Graben Sand Formation is now included in the revised Bryne Formation. The Lulu Formation is erected to include the uppermost part of the Middle Jurassic succession, previously referred to the Bryne Formation in the northern Danish Central Graben. The Upper Jurassic Heno Formation is subdivided into two new members, the Gert Member (lower) and the Ravn Member (upper). The organic-rich part of the upper Farsund Formation, the former informal ‘hot unit’, is established formally as the Bo Member. Dominantly shallow marine and paralic deposition in the Late Triassic was succeeded by widespread deposition of offshore marine clays in the Early Jurassic. On Bornholm, coastal and paralic sedimentation prevailed. During maximum transgression in the Early Toarcian, sedimentation of organic-rich offshore clays took place in the Danish area. This depositional phase was terminated by a regional erosional event in early Middle Jurassic time, caused by uplift of the central North Sea area, including the Ringkøbing–Fyn High. In the Sorgenfrei–Tornquist Zone to the east, where slow subsidence continued, marine sandy sediments were deposited in response to the uplift. Uplift of the central North Sea area was followed by fault-controlled subsidence accompanied by fluvial and floodplain deposition during Middle Jurassic time. On Bornholm, deposition of lacustrine muds, fluvial sands and peats dominated. The late Middle Jurassic saw a gradual shift to shallow marine deposition in the Danish Central Graben, the Danish Basin and Skåne, southern Sweden. During the Late Jurassic, open marine shelf conditions prevailed with deposition of clay-dominated sediments while shallow marine sands were deposited on platform areas. The Central Graben received sand by means of sediment gravity flows. The clay sediments in the Central Graben became increasingly rich in organic matter at the Jurassic–Cretaceous transition, whilst shallow marine coarse-grained deposits prograded basinwards in the Sorgenfrei– Tornquist Zone.
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Anderton, R., W. Gibbons, and P. G. Nicholson. "Precambrian." Geological Society, London, Memoirs 13, no. 1 (1992): 5–12. http://dx.doi.org/10.1144/gsl.mem.1992.013.01.04.
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AbstractFor much of Precambrian time, it is not possible to reconstruct any sort of meaningful palaeogeographies. For this Atlas, therefore, the earliest reconstructions are for Proterozoic intervals and are, of necessity, limited geographically.The term 'Torridonian' has long since been used to refer to the entire Upper Proterozoic succession of predominantly fluvial clastic sediments situated along the northwest coast of Scotland. These rocks rest unconformably on Archaean to Lower Proterozoic Lewisian Gneiss, are overlain unconformably by Cambro-Ordovician marine sediments, and constitute the best sedimentary exposures in the British Isles. Stratigraphically, 'Torridonian' deposits are subdivided into the Stoer, Sleat and Torridon groups. The Stoer and Torridon groups are separated by an angular unconformity (Lawson 1965; Stewart 1969) and have been dated at 968 and 777 Ma respectively (Moorbath 1969; Stewart 1982), although these ages may be up to 100 Ma too young (see discussion in Stewart 1988a, p. 98). Sedimentation dates of c. 1050 (Stoer Group) and c. 850 (Torridon Group) are, therefore, likely to be more realistic.The lowest of the three groups consists of a diverse suite of red bed deposits up to 2 km thick representing fluvial, aeolian and ephemeral lacustrine environments, suggesting a semi-arid climate (Stewart 1988a). Deposition occurred at an approximate palaeolatitude of 15°N (Torsvik & Sturt 1987). Stoer Group sediments have been divided by Stewart (1988a) into seven constituent facies. The illustrated palaeogeographical time interval encompasses the end of Bay of Stoer facies deposition, theThe Bay .of Stoer facies consists of roughly 200 m
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FRIEND, P. F., W. B. HARLAND, D. A. ROGERS, I. SNAPE, and R. S. W. THORNLEY. "Late Silurian and Early Devonian stratigraphy and probable strike-slip tectonics in northwestern Spitsbergen." Geological Magazine 134, no. 4 (July 1997): 459–79. http://dx.doi.org/10.1017/s0016756897007231.
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The stratigraphy of the Siktefjellet and Red Bay groups of northwestern Spitsbergen is revised in the light of new fieldwork. An early Early Devonian (Lochkovian) age is indicated by the rich fossil vertebrate faunas of the Red Bay Group. The underlying Siktefjellet Group is likely to be Late Silurian in age, although there is no direct fossil evidence of this. The most abundant sediment type in the two groups is fine-grained fluvial sandstone, although conglomerates and lacustrine siltstones also occur. The conglomerates that predominate in the lowest parts of both groups imply the presence of fault scarps at the surface. There has been much debate about the importance of strike-slip faulting in the area, particularly in relation to the major north–south trending Raudfjorden and Breibogen faults. Between these faults, the Biskayerhuken–Holtedahlfonna terrane contains a zone for which the deliberately genetic name ‘Siktefjellet Strike-slip Zone’ is proposed. This zone is characterized by evidence for a succession of events that, taken together, suggest a history of continuing, repeated strike-slip. These events were: (1) the tectonism and metamorphism of the basement (Krossfjorden Group) and the emplacement of the high-grade Richarddalen Complex, (2) development of crush zones in the basement, (3) deposition of the Siktefjellet Group in two distinct basins (perhaps of pull-apart origin), (4) deposition of the Red Bay Group (first as discrete scarp-related conglomerates, and then as part of a more stable fluvial basin), (5) localized compressional deformation of the Siktefjellet and Red Bay groups.
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Sierra-Rojas, María I., Roberto S. Molina-Garza, and Timothy F. Lawton. "The Lower Cretaceous Atzompa Formation In South-Central Mexico: Record of Evolution From Extensional Backarc Basin Margin To Carbonate Platform." Journal of Sedimentary Research 86, no. 6 (June 1, 2016): 712–33. http://dx.doi.org/10.2110/jsr.2016.45.
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Abstract: Lower Cretaceous depositional systems of southwestern Oaxaquia, in south-central Mexico, were influenced by initiation of a continental arc on mainland Mexico and subsequent accretion of the Guerrero composite arc terrane to mainland Mexico. The Atzompa Formation, defined herein, which crops out in the Sierra de Tentzo, constitutes a succession of conglomerate, sandstone, siltstone, and limestone with Early Cretaceous fauna and detrital zircon maximum depositional ages that range 126–123 Ma (late Barremian to early Aptian). The lower part of the Atzompa records a transition from alluvial to deep lacustrine depositional environments, suggesting the early stages of an extensional basin; overlying deposits of anabranching axial fluvial systems that flowed to the NE–SE accumulated after a period of rapid subsidence in the Tentzo basin, also formerly undescribed. Fluvial facies grade up-section to tidal deposits overlain in turn by a carbonate ramp succession that contains late Barremian to early Aptian fossils. The ramp deposits of the uppermost Atzompa Formation are overlain on a sharp contact by basinal carbonates of early Albian age.The Tentzo basin, formed due to crustal extension of the overriding plate in a backarc setting, was characterized by very high rates of sedimentation (3.6 mm/yr) during the early stages of basin formation (rift initiation and rift climax), and slower rates during the development of tidal systems and the carbonate ramp (post-rift stage). Regional and local subsidence took place in the backarc region of the Zicapa magmatic arc, which was established in the western margin of Mexico by Hauterivian time. Abrupt deepening following Atzompa Formation deposition is attributed to flexural subsidence related to collision of the Guerrero composite volcanic terrane with the western margin of Mexico. Following late Aptian accretion of the Guerrero terrane to Oaxaquia, the carbonate basin eventually shallowed to become a carbonate platform that faced the Gulf of Mexico.
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Adhikari, Basanta Raj, and Khum Narayan Paudayal. "Palynological evidence for the Neogene environment analysis of the Thakkhola Graben, Nepal." Journal of Nepal Geological Society 60 (September 16, 2020): 117–29. http://dx.doi.org/10.3126/jngs.v60i0.31260.
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The Thakkhola Graben, a north-south graben, lies in central Nepal Himalayas consisting of Neogene sediments. The presence of pollens in these sediments provides a unique natural laboratory to understand the paleoenvironment during the formation of the graben. This study provides a detailed description of the pollen collected from the Tetang and Thakkhola formations with the help of the Light Microscope and Scanning Electron Microscope. A variety of pollen assemblages from the Thakkhola Graben explains that the sediments contain dominant alpine trees with some steppe vegetation. Presence of evergreen subtropical and temperate deciduous broad-leaved forest, needle-leaved element, and high altitude taxa show a mixed pollen assemblage in fluvial-lacustrine sediments of the graben. The presence of evergreen subtropical and temperate deciduous broadleaf forest (Quercus, Betula, Juglans, Alnus), needle-leaved element (Pinus, Tsuga) and high altitude taxa (Picea, Abies) with Artemisia, Chenopodiaceae, Poaceae, Rosaceae show mixed pollen assemblages indicating warm and humid paleoclimate. The coniferous pollen indicates the altitude was higher during the deposition time and the presence of Betula, Quercus, and Juglans suggests temperate forest. Domination of Artemisia and Chenopodiaceae shows a strong influence of the Himalayan topographic barrier during the sediment deposition.
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Tanner, Lawrence H., and Spencer G. Lucas. "Deposition and deformation of fluvial–lacustrine sediments of the Upper Triassic–Lower Jurassic Whitmore Point Member, Moenave Formation, northern Arizona." Sedimentary Geology 223, no. 1-2 (January 2010): 180–91. http://dx.doi.org/10.1016/j.sedgeo.2009.11.010.
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Hamilton, D. S., P. G. Ryles, T. P. Lonergan, M. G. Hillyer, and M. H. Holtz. "APPROACHES TO IDENTIFYING RESERVOIR HETEROGENEITY AND RESERVE GROWTH OPPORTUNITIES IN THE HUTTON SANDSTONE, JACKSON FIELD, AUSTRALIA." APPEA Journal 37, no. 1 (1997): 48. http://dx.doi.org/10.1071/aj96003.
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An integrated geologic and engineering approach was applied to identify heterogeneities in the subsurface that might lead to reserve growth opportunities in the analysis of the Hutton Sandstone within the Jackson field, Eromanga Basin, Australia. The devised approach involves four key steps:determine geologic reservoir architecture;investigate trends in reservoir fluid flow;integrate fluid flow trends with reservoir architecture; andestimate original oil-in-place, residual oil saturation, and remaining mobile oil, to identify opportunities for reserve growth.Although the Hutton reservoir is interpreted as the deposit of a continental-scale bed-load fluvial system and is dominated by highly permeable sandstone, the genetic stratigraphic analysis identified numerous thin but widespread lacustrine shale units that periodically interrupted episodes of coarse clastic Hutton deposition. These shales represent chrono-stratigraphically significant surfaces, but more importantly, the trends established in reservoir fluid flow from monitoring aquifer encroachment, production response to workovers, and differential depletion indicate that these shale units act as efficient barriers to vertical fluid flow. Erosion of the upper part of the Hutton reservoir by the younger Birkhead mixed-load fluvial system caused further strati- graphic complexity introducing additional barriers to vertical and lateral migration of mobile oil and aquifer encroachment. These stratigraphic complexities were not fully appreciated in previous field development and production strategies and potential exists for incremental reserve growth through geologically-targeted infill drilling and recompletions.
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Paudyal, Khum Narayan, Sudarshan Bhandari, and Arata Momohara. "Late Quaternary plant macrofossil assemblages from the Besigaon section of the Gokarna Formation, Kathmandu Valley, central Nepal." Journal of Nepal Geological Society 42 (September 24, 2011): 1–12. http://dx.doi.org/10.3126/jngs.v42i0.31440.
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Plant macrofossil investigation was carried out on the Late Quaternary sediments of the Kathmandu Valley, central Nepal. The fluvial-deltaic to fluvio-lacustrine deposits of the Kathmandu Basin are found to be rich in plant macrofossil assemblages. A total of 66tax.a from 38 families were identified to genus and some of them up to species level from five different macrofossil bearing layers (BG- I Lo BG-5) from the 33 m thick Besigaon section belonging to the Gokarna Formation exposed at the northern part of the basin. The lower half of the exposed section is completely devoid of macrofossil horizons, however the upper half yielded a significant amount which could be used for climatic interpretation. The characteristic feature of the Besigaon section is the dominance of angiosperms in the lower and middle horizons (BG-I, BG-2, BG-3) but gymnosperms in the upper horizons (BG-4, BG-5). The dominance of angiosperms such as Carpinus, Alnus, Pyracantha, Quercus subgen. Cyclobalanopsis, Eurya and Zizyphus suggest the deposition of the lower and middle horizons in warm temperate climatic condition. The humid phase is documented during deposition of the BG-3 and BG-4 horizons with the findings of Selaginella remotifolia and wetland aquatic taxa such Carex, Schoenoplectus, Nymphoides indica. In contrast, the upper horizons dominated by gymnosperms such as Abies, Pinus, Picea smithiana, Tsuga dumosa and Taxus wallichiana represent cold and humid climate. The macrofossils from Besigaon section suggest minor fluctuation in climate from wam1to cold temperate phase with increasing humidity during the Late Pleistocene.
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Riggs, N. R., T. B. Sanchez, and S. J. Reynolds. "Evolution of the early Mesozoic Cordilleran arc: The detrital zircon record of back-arc basin deposits, Triassic Buckskin Formation, western Arizona and southeastern California, USA." Geosphere 16, no. 4 (June 30, 2020): 1042–57. http://dx.doi.org/10.1130/ges02193.1.
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Abstract A shift in the depositional systems and tectonic regime along the western margin of Laurentia marked the end of the Paleozoic Era. The record of this transition and the inception and tectonic development of the Permo-Triassic Cordilleran magmatic arc is preserved in plutonic rocks in southwestern North America, in successions in the distal back-arc region on the Colorado Plateau, and in the more proximal back-arc region in the rocks of the Buckskin Formation of southeastern California and west-central Arizona (southwestern North America). The Buckskin Formation is correlated to the Lower–Middle Triassic Moenkopi and Upper Triassic Chinle Formations of the Colorado Plateau based on stratigraphic facies and position and new detrital zircon data. Calcareous, fine- to medium-grained and locally gypsiferous quartzites (quartz siltstone) of the lower and quartzite members of the Buckskin Formation were deposited in a marginal-marine environment between ca. 250 and 245 Ma, based on detrital zircon U-Pb data analysis, matching a detrital-zircon maximum depositional age of 250 Ma from the Holbrook Member of the Moenkopi Formation. An unconformity that separates the quartzite and phyllite members is inferred to be the Tr-3 unconformity that is documented across the Colorado Plateau, and marks a transition in depositional environments. Rocks of the phyllite and upper members were deposited in wholly continental depositional environments beginning at ca. 220 Ma. Lenticular bodies of pebble to cobble (meta) conglomerate and medium- to coarse-grained phyllite (subfeldspathic or quartz wacke) in the phyllite member indicate deposition in fluvial systems, whereas the fine- to medium-grained beds of quartzite (quartz arenite) in the upper member indicate deposition in fluvial and shallow-lacustrine environments. The lower and phyllite members show very strong age and Th/U overlap with grains derived from Cordilleran arc plutons. A normalized-distribution plot of Triassic ages across southwestern North America shows peak magmatism at ca. 260–250 Ma and 230–210 Ma, with relatively less activity at ca. 240 Ma, when a land bridge between the arc and the continent was established. Ages and facies of the Buckskin Formation provide insight into the tectono-magmatic evolution of early Mesozoic southwestern North America. During deposition of the lower and quartzite members, the Cordilleran arc was offshore and likely dominantly marine. Sedimentation patterns were most strongly influenced by the Sonoma orogeny in northern Nevada and Utah (USA). The Tr-3 unconformity corresponds to both a lull in magmatism and the “shoaling” of the arc. The phyllite and upper members were deposited in a sedimentary system that was still influenced by a strong contribution of detritus from headwaters far to the southeast, but more locally by a developing arc that had a far stronger effect on sedimentation than the initial phases of magmatism during deposition of the basal members.
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Elson, Amy, John Marshall, and Jessica Whiteside. "Controls on organic matter variation during deposition of the Mahogany Oil Shale Zone of the Parachute Creek Member, Green River Formation, Utah." Geosites 50 (September 1, 2022): 1–19. http://dx.doi.org/10.31711/ugap.v50i.110.
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The Green River Formation of Utah, Colorado, and Wyoming represents a ~10 million-year early-middle Eocene record of an unusually large, productive lacustrine system composed of several interconnected basins. This system gave rise to one of the largest oil shale deposits in the world, which preserves a rich trove of information about the climate and ecosystems that prevailed during the Early Eocene Climatic Optimum. This study uses multiple analytical approaches, including both traditional methods and novel proxies, to determine what brought about the accumulation of the unusually-rich oil shales (>40% TOC) of the Mahogany Zone in the Uinta Basin portion of the Green River Formation. The organic-rich mudstones of the Mahogany Zone exhibit strong micro-scale heterogeneity, indicating complex controls on organic matter production and distribution. Petrographic observations indicate highly variable amounts of terrestrial organic matter (spores, wood and plant debris), with the most abundant being amorphous organic material in thin organic-rich laminae. Biomarker ratios indicate that the organic-rich laminae consist of different types of microbially derived organic matter, primarily bituminite and organo-minerallic aggregates of the fluorescent liptinite group. These largely lacustrine-derived laminated deposits are argued to have been produced by large intrato inter-annual algal blooms and other enhanced microbial productivity events paced by longer-term sub-orbital cycle fluctuations, such as El Niño–Southern Oscillation or sunspot variations. The Mahogany Zone deposits appear to have sequestered enough carbon (~64.25 Gt estimated) to suggest that, in aggregate, they were large enough to cause a draw-down of terrestrial CO2 and exert a significant negative feedback effect on climatic warming. During the climatic cooling that occurred on the declining limb of the Early Eocene Climatic Optimum, the sedimentary provenance in the Uinta Basin shifted from southerly sources dominated by large ephemeral fluvial systems, to northerly sources rich in feldspathic and carbonate detritus derived from northern sites in Wyoming. The latter were delivered to the Uinta Basin via a network of interconnected lacustrine basins. Increasing volcaniclastic material delivered from these northerly basins infilled the Uinta Basin from east to west, and their arrival heralded the end of organic-rich deposition, most notably the prolific oil shales for which the Green River Formation is renowned.
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Rivett, Michael O., Shona Symon, Lucas Jacobs, Limbikani C. Banda, Gift J. Wanangwa, Donald J. C. Robertson, Ibrahim Hassan, et al. "Paleo-Geohydrology of Lake Chilwa, Malawi is the Source of Localised Groundwater Salinity and Rural Water Supply Challenges." Applied Sciences 10, no. 19 (October 2, 2020): 6909. http://dx.doi.org/10.3390/app10196909.
Full textAbstract:
Meeting long-term rural community water supply needs requires diligent geohydrological conceptualisation. Study of Malawi’s Lake Chilwa Basin, including sampling of 330 water points in Phalombe District, enabled assessment of groundwater quality influence upon supply. The control of larger Lake Chilwa paleo-environments on current Basin groundwater quality is demonstrated. Lacustrine sediment deposition forming high-level deposits under open lake conditions and terrace deposits under open and closed lake conditions significantly control the groundwater major-ion quality and salinity now observed. Paleo-lake extent marks the transition between low-TDS (total dissolved solids) groundwater suitable for water supply at higher elevations and high-TDS brackish groundwater in areas overlain by lacustrine deposits closer to the current lake level. Low-TDS groundwater is limited to mid-to-low reach influent leakage of rivers incising terraces. Permeable fluvial deposits within the deeper paleo-river channel may possibly provide low-TDS water. The conceptual model, whereby paleo-lake controls groundwater salinity, provides science-based evidence to address policy to manage the significant water point functionality concerns quantified at the district and river basin scales. Targeting of the low-TDS groundwater alongside improved use of upland low-TDS stream/river sources with fewer, but larger capacity, and better maintained gravity-fed supply schemes are recommended. This study hence shows the value of paleo-geohydrology interpretation of the lake–groundwater system conceptualisation to inform Sustainable Development Goal 6 (SDG 6.5.1)—integrated water resources management policy for rural water supply.
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Birgenheier, L. P., M. D. Vanden Berg, P. Plink-Björklund, R. D. Gall, E. Rosencrans, M. J. Rosenberg, L. C. Toms, and J. Morris. "Climate impact on fluvial-lake system evolution, Eocene Green River Formation, Uinta Basin, Utah, USA." GSA Bulletin 132, no. 3-4 (June 19, 2019): 562–87. http://dx.doi.org/10.1130/b31808.1.
Full textAbstract:
Abstract In light of a modern understanding of early Eocene greenhouse climate fluctuations and new highly seasonal fluvial system faces models, the role of climate in the evolution of one classically-cited continental, terminal lake system is re-examined. Detailed stratigraphic description and elemental abundance data from fifteen cores and seven outcrop regions of the Green River Formation were used to construct a ∼150 km cross section across the Uinta Basin, Utah, USA. Lake Uinta in the Uinta Basin is divided into five lake phases: (1) post-Paleocene Eocene Thermal Maximum, (2) peak Eocene hyperthermal, (3) waning hyperthermal, Early Eocene Climatic Optimum (EECO), (4) post-hyperthermal, and (5) post-EECO regimes, based primarily on climatically driven changes in fluvial style in combination with sedimentary indicators of lacustrine carbonate deposition, organic matter preservation, salinity, and lake depth. Basinwide siliciclastic dominated intervals were deposited by highly seasonal fluvial systems and record negative organic carbon isotope excursions associated with early Eocene abrupt, transient global warming (hyperthermal) events. Carbonate dominated or organic rich intervals record stable, less seasonal climate periods between hyperthermals, with lower siliciclastic sediment supply allowing the development of carbonate and organic matter preservation. The stratigraphic progression from alternating organic rich and lean zones to the overlying organic rich Mahogany and R8 zones represents the global transition out of the pulsed early Eocene hyperthermal climate regime to a time of sediment starvation and lake stratification, sequestering sedimentary organic carbon. This study provides a novel approach to terrestrial paleoclimate reconstruction that relies largely on unique sedimentary indicators and secondarily on isotopic proxy records within the context of a large basin-wide sedimentologic and stratigraphic data set, thus setting the stage for future detailed geochemical terrestrial paleoclimate proxy development.