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1
Liu, Chao, Hai Tao Xue, Shuang Wang e Yu Jiao Sun. "Study on Law of Structural Evolution and Sedimentary Evolution for North Uskyurt Basin". Advanced Materials Research 671-674 (marzo 2013): 302–5. http://dx.doi.org/10.4028/www.scientific.net/amr.671-674.302.
Testo completoAbstract (sommario):
North Uskyurt Basin, located on Turan Plain, northwestern Central Asian, is continental polycyclic cratonic. The structural evolution of the basin underwent six phases: basement formulation, passive edge, rifting, post-rifting, compression, early Neogene depression. Regional structural evolution takes control of complicated transition of North Uskyurt sedimentary structure. In general, basin sedimentary environment underwent basement (granite, metamorphic rocks) passive edge, late Devonian epoch carboniferous period (marine facies) rifting, late Permian epoch-triassic period (continental facies) post-rifting, Jurassic period-Cretaceous period (Marine-continental Transition Facies, marine facies) compression, late Eocene-Miocene epoch (marine-continental facies coexistence) Neogene depression, Pliocene-Holocene (continental facies). Consequently, sedimentary formation in which various sedimentary environment, such as marine facies, continental facies, are coexisted with various rock types, such as clastic rocks, carbonate rocks, is generated.
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Bera, M. K., A. Sarkar, P. P. Chakraborty, R. S. Loyal e P. Sanyal. "Marine to continental transition in Himalayan foreland". Geological Society of America Bulletin 120, n. 9-10 (1 settembre 2008): 1214–32. http://dx.doi.org/10.1130/b26265.1.
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Singh, B. P. "Marine to continental transition in Himalayan foreland: Discussion". Geological Society of America Bulletin 122, n. 5-6 (6 aprile 2010): 954–55. http://dx.doi.org/10.1130/b26532.1.
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Bera, M. K., A. Sarkar, P. P. Chakraborty, R. S. Loyal e P. Sanyal. "Marine to continental transition in Himalayan foreland: Reply". Geological Society of America Bulletin 122, n. 5-6 (6 aprile 2010): 956–59. http://dx.doi.org/10.1130/b26591.1.
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Wei, Zhifu, Yongli Wang, Gen Wang, Ting Zhang, Wei He, Xueyun Ma e Xiaoli Yu. "Enrichment Mechanism of the Upper Carboniferous-Lower Permian Transitional Shale in the East Margin of the Ordos Basin, China: Evidence from Geochemical Proxies". Geofluids 2020 (6 novembre 2020): 1–14. http://dx.doi.org/10.1155/2020/8867140.
Testo completoAbstract (sommario):
The organic-rich shale of the Upper Carboniferous-Lower Permian transition period in the eastern margin of the Ordos Basin, China, was formed in a marine-continental facies sedimentary environment. With a high content of total organic carbon (TOC) and a large cumulative thickness, it is considered a good source rock for shale gas development. The sedimentary environment of marine-continental transitional shale is obviously different from that of marine shale, which leads to different enrichment characteristics of organic matter. In this paper, shale samples were collected from XX# well of the Taiyuan and Shanxi Formations across the Upper Carboniferous-Lower Permian, which is typical marine-continental transitional shale. The TOC, major elements, and trace elements were measured, and the formation and preservation conditions were investigated using multiple geochemical proxies, including paleoclimate, redox parameters, paleoproductivity, and controls on the accumulation of organic matter. The TOC of Shanxi Formation is higher than that of Taiyuan Formation. In the Taiyuan Formation, TOC is positively related to the redox index (V, U, and V/Cr), indicating that the dysoxic bottom water environment is the key factor controlling organic matter accumulation. For Shanxi Formation, there is a positive correlation between TOC and paleoclimate, which indicates that the enrichment of organic matter is affected by warm and humid paleoclimate and oxic environment. In addition, the paleoproductivity is lower with a positive correlation with TOC for the marine-continental transitional organic-rich shale, suggesting that it was inferior to the gathering of organic matter.
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Cui, Z., S. Davies, K. S. Carslaw e A. M. Blyth. "The response of precipitation to aerosol through riming and melting in deep convective clouds". Atmospheric Chemistry and Physics Discussions 10, n. 11 (25 novembre 2010): 29007–50. http://dx.doi.org/10.5194/acpd-10-29007-2010.
Testo completoAbstract (sommario):
Abstract. We have used a 2-D axisymmetric, non-hydrostatic, bin-resolved cloud model to examine the impact of aerosol changes on the development of mixed-phase convective clouds. We have simulated convective clouds from four different sites (three continental and one tropical marine) with a wide range of realistic aerosol loadings and initial thermodynamic conditions (a total of 93 different clouds). It is found that the accumulated precipitation responds very differently to changing aerosol in the marine and continental environments. For the continental clouds, the scaled total precipitation reaches a maximum for aerosol that produce drop numbers at cloud base between 180–430 cm−3 when other conditions are the same. In contrast, all the tropical marine clouds show an increase in accumulated precipitation and deeper convection with increasing aerosol loading. For continental clouds, drops are rapidly depleted by ice particles shortly after the onset of precipitation. The precipitation is dominantly produced by melting ice particles. The riming rate increases with aerosol when the loading is very low, and decreases when the loading is high. Peak precipitation intensities tend to increase with aerosol up to drop concentrations (at cloud base) of ~500 cm−3 then decrease with further aerosol increases. This behaviour is caused by the initial transition from warm to mixed-phase rain followed by reduced efficiency of mixed-phase rain at very high drop concentrations. The response of tropical marine clouds to increasing aerosol is different to, and larger than, that of continental clouds. In the more humid tropical marine environment with low cloud bases we find that accumulated precipitation increases with increasing aerosol. The increase is driven by the transition from warm to mixed-phase rain. Our study suggests that the response of deep convective clouds to aerosol will be an important contribution to the spatial and temporal variability in cloud microphysics and precipitation.
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Cui, Z., S. Davies, K. S. Carslaw e A. M. Blyth. "The response of precipitation to aerosol through riming and melting in deep convective clouds". Atmospheric Chemistry and Physics 11, n. 7 (15 aprile 2011): 3495–510. http://dx.doi.org/10.5194/acp-11-3495-2011.
Testo completoAbstract (sommario):
Abstract. We have used a 2-D axisymmetric, non-hydrostatic, bin-resolved cloud model to examine the impact of aerosol changes on the development of mixed-phase convective clouds. We have simulated convective clouds from four different sites (three continental and one tropical marine) with a wide range of realistic aerosol loadings and initial thermodynamic conditions (a total of 93 different clouds). It is found that the accumulated precipitation responds very differently to changing aerosol in the marine and continental environments. For the continental clouds, the scaled total precipitation reaches a maximum for aerosol that produce drop numbers at cloud base between 180–430 cm−3 when other conditions are the same. In contrast, all the tropical marine clouds show an increase in accumulated precipitation and deeper convection with increasing aerosol loading. For continental clouds, drops are rapidly depleted by ice particles shortly after the onset of precipitation. The precipitation is dominantly produced by melting ice particles. The riming rate increases with aerosol when the loading is very low, and decreases when the loading is high. Peak precipitation intensities tend to increase with aerosol up to drop concentrations (at cloud base) of ~500 cm−3 then decrease with further aerosol increases. This behaviour is caused by the initial transition from warm to mixed-phase rain followed by reduced efficiency of mixed-phase rain at very high drop concentrations. The response of tropical marine clouds to increasing aerosol is different to, and larger than, that of continental clouds. In the more humid tropical marine environment with low cloud bases we find that accumulated precipitation increases with increasing aerosol. The increase is driven by the transition from warm to mixed-phase rain. Our study suggests that the response of deep convective clouds to aerosol will be an important contribution to the spatial and temporal variability in cloud microphysics and precipitation.
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Ning, Shitan, Peng Xia, Fang Hao, Jinqiang Tian, Yong Fu e Ke Wang. "Pore Fractal Characteristics between Marine and Marine–Continental Transitional Black Shales: A Case Study of Niutitang Formation and Longtan Formation". Fractal and Fractional 8, n. 5 (13 maggio 2024): 288. http://dx.doi.org/10.3390/fractalfract8050288.
Testo completoAbstract (sommario):
Marine shales from the Niutitang Formation and marine–continental transitional shales from the Longtan Formation are two sets of extremely important hydrocarbon source rocks in South China. In order to quantitatively compare the pore complexity characteristics between marine and marine–continental transitional shales, the shale and kerogen of the Niutitang Formation and the Longtan Formation are taken as our research subjects. Based on organic petrology, geochemistry, and low-temperature gas adsorption analyses, the fractal dimension of their pores is calculated by the Frenkel–Halsey–Hill (FHH) and Sierpinski models, and the influences of total organic carbon (TOC), vitrinite reflectance (Ro), and mineral composition on the pore fractals of the shale and kerogen are discussed. Our results show the following: (1) Marine shale predominantly has wedge-shaped and slit pores, while marine–continental transitional shale has inkpot-shaped and slit pores. (2) Cylindrical pores are common in organic matter of both shale types, with marine shale having a greater gas storage space (CRV) from organic matter pores, while marine–continental transitional shale relies more on inorganic pores, especially interlayer clay mineral pores, for gas storage due to their large specific surface area and high adsorption capacity (CRA). (3) The fractal characteristics of marine and marine–continental transitional shale pores are influenced differently. In marine shale, TOC positively correlates with fractal dimensions, while in marine–continental shale, Ro and clay minerals have a stronger influence. Ro is the primary factor affecting organic matter pore complexity. (4) Our two pore fractal models show that the complexity of the shale in the Longtan Formation surpasses that of the shale in the Niutitang Formation, and type I kerogen has more complex organic matter pores than type III, aiding in evaluating pore connectivity and flow effectiveness in shale reservoirs.
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Monesi, Edoardo, Giovanni Muttoni, Giancarlo Scardia, Fabrizio Felletti, Fabio Bona, Benedetto Sala, Fabrizio Tremolada, Carlo Francou e Gianluca Raineri. "Insights on the opening of the Galerian mammal migration pathway from magnetostratigraphy of the Pleistocene marine-continental transition in the Arda River section (northern Italy)". Quaternary Research 86, n. 2 (settembre 2016): 220–31. http://dx.doi.org/10.1016/j.yqres.2016.07.006.
Testo completoAbstract (sommario):
AbstractWe investigated the magnetostratigraphy of the Arda River section (northern Italy) where the transition from marine to continental sedimentation occurring in the Po River basin during the Pleistocene is registered. Four magnetic polarity reversals were used to construct an age model of sedimentation aided by marine biostratigraphy and tied to a standard δ18O curve from the literature. The section spans from the Olduvai subchron (1.94-1.78 Ma) across the Jaramillo subchron (1.07-0.99 Ma) up to the Brunhes—Matuyama boundary (0.78 Ma). The onset of continental deposition occurred during marine isotope stage (MIS) 30 at ∼1.04 Ma. An association of Villafranchian and Early Galerian mammals, including Sus strozzii and Ursus dolinensis, has been found in the continental sediments dated to MIS 29-27 (∼0.99 Ma). Above follows a prominent fluvial conglomerate attributed to the first major low stand of the Pleistocene culminating with MIS 22 at ∼0.9 Ma during the late Early Pleistocene climate turnover (EPT). These and other data from the literature are used to reconstruct the onset of continental deposition in the greater Po basin and shed light on the opening of the migration pathway that brought far-traveled Galerian mammal immigrants to enter Europe for the first time during the EPT.
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Mourier, Thomas, Peter Bengtson, Michel Bonhomme, Emile Buge, Henri Cappettta, Jean-Yves Crochet, Monique Feist et al. "The Upper Cretaceous - Lower Tertiary marine to continental transition in the Bagua basin, northern Peru - Paleontology, biostratigraphy, radiometry, correlations". Newsletters on Stratigraphy 19, n. 3 (26 ottobre 1988): 143–77. http://dx.doi.org/10.1127/nos/19/1988/143.
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Mai, Ana C. G., Lizandra J. Robe, Luis F. Marins e João P. Vieira. "Genetic relationships between landlocked and coastal populations of Lycengraulis grossidens (Engraulidae) in south-eastern South America: evidence for a continental colonisation route with secondary transitions to the coastal region". Marine and Freshwater Research 68, n. 2 (2017): 342. http://dx.doi.org/10.1071/mf15355.
Testo completoAbstract (sommario):
The anchovies of the genus Lycengraulis are the product of an evolutionary transition from a marine to freshwater environment that occurred in South America during the Miocene epoch. Lycengraulis grossidens originated from freshwater lineages and is currently distributed in estuaries and coastal zones. Nevertheless, based on otolith chemistry, there are landlocked individuals in the Uruguay River. The aim of the present study was to investigate the spatiotemporal scenario by which these landlocked individuals reached their current distribution: whether through a north-to-south continental route based on the connection between basins or from the marine environment. To this end, a fragment of the mitochondrial (mt)DNA control region was analysed from individuals collected along freshwater, estuarine and marine environments. We found a significant genetic differentiation between freshwater and coastal (estuarine and marine) populations. Larger haplotype diversities and female effective population size values were found in the coastal population. Nevertheless, the outgroup rooting positioned some Uruguay River haplotypes as hypothetical ancestors in the directed network and as early offshoots in the phylogeny, suggesting the landlocked population as an ancestral lineage. Therefore, the phylogenetic history and biogeography are consistent with a north-to-south continental colonisation route putatively associated with ancient connections between the Amazon and Parana basins followed by new evolutionary transitions to the coastal region associated with Quaternary sea level oscillations.
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Coram, Robert A., Jonathan D. Radley e Andrew J. Webster. "Continental bookends—the arrival and departure of the Jurassic Sea in southern England". Geology Today 39, n. 5 (settembre 2023): 189–95. http://dx.doi.org/10.1111/gto.12449.
Testo completoAbstract (sommario):
Rocks laid down during the Jurassic Period (201–143 Ma) in southern England are almost exclusively marine, but are sandwiched between continental deposits of the Late Triassic and Early Cretaceous. The transitions from fully continental to marine then back to continental, in response to continent movements and sea level change, mirror each other in important respects, taking place via intermediate environments which, although separated by approximately 60 million years, show remarkable similarities in their rocks and faunas.
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van der Ploeg, Robin, Bernard P. Boudreau, Jack J. Middelburg e Appy Sluijs. "Cenozoic carbonate burial along continental margins". Geology 47, n. 11 (6 settembre 2019): 1025–28. http://dx.doi.org/10.1130/g46418.1.
Testo completoAbstract (sommario):
Abstract Marine carbonate burial represents the largest long-term carbon sink at Earth’s surface, occurring in both deep-sea (pelagic) environments and shallower waters along continental margins. The distribution of carbonate accumulation has varied over geological history and impacts the carbon cycle and ocean chemistry, but it remains difficult to quantitatively constrain. Here, we reconstruct Cenozoic carbonate burial along continental margins using a mass balance for global carbonate alkalinity, which integrates independent estimates for continental weathering and pelagic carbonate burial. Our results indicate that major changes in marginal carbonate burial were associated with important climate and sea-level change events, including the Eocene-Oligocene transition (ca. 34 Ma), the Oligocene-Miocene boundary Mi-1 glaciation (ca. 23 Ma), and the middle Miocene climate transition (ca. 14 Ma). In addition, we find that a major increase in continental weathering from ca. 10 Ma to the present may have driven a concomitant increase in pelagic carbonate burial. Together, our results show that changes in global climate, sea level, and continental weathering have all impacted carbonate burial over the Cenozoic, but the relative importance of these processes may have varied through time.
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Fisher, Erich C., Hayley C. Cawthra, Irene Esteban, Antonieta Jerardino, Frank H. Neumann, Annette Oertle, Justin Pargeter et al. "Coastal occupation and foraging during the last glacial maximum and early Holocene at Waterfall Bluff, eastern Pondoland, South Africa". Quaternary Research 97 (14 maggio 2020): 1–41. http://dx.doi.org/10.1017/qua.2020.26.
Testo completoAbstract (sommario):
AbstractWaterfall Bluff is a rock shelter in eastern Pondoland, South Africa, adjacent to a narrow continental shelf that limited coastline movements across glacial/interglacial cycles. The archaeological deposits are characterized by well-preserved stratigraphy, faunal, and botanical remains alongside abundant stone artifacts and other materials. A comprehensive dating protocol consisting of 5 optically stimulated luminescence ages and 51 accelerator mass spectrometry 14C ages shows that the record of hunter-gatherer occupations at Waterfall Bluff persisted from the late Pleistocene to the Holocene, spanning the last glacial maximum and the transition from the Pleistocene to the Holocene. Here, we provide detailed descriptions about the sedimentary sequence, chronology, and characteristics of the archaeological deposits at Waterfall Bluff. Remains of marine mollusks and marine fish also show, for the first time, that coastal foraging was a component of some hunter-gatherer groups’ subsistence practices during glacial phases in the late Pleistocene. The presence of marine fish and shellfish further demonstrates that hunter-gatherers selectively targeted coastal resources from intertidal and estuarine habitats. Our results therefore underscore the idea that Pondoland's coastline remained a stable and predictable point on the landscape over the last glacial/interglacial transition being well positioned for hunter-gatherers to access resources from the nearby coastline, narrow continental shelf, and inland areas.
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Nieto, Luis M., José Miguel Molina, Pedro Alejandro Ruiz-Ortiz, José Manuel Castro, Matías Reolid e Ginés A. de Gea. "Palustrine Sediments between Two Isolated Shallow Carbonate Platforms (Aptian–Albian Transition, Prebetic of Jaén, South Spain)". Minerals 12, n. 2 (20 gennaio 2022): 116. http://dx.doi.org/10.3390/min12020116.
Testo completoAbstract (sommario):
During the Aptian-Albian transition, an extensional phase of the Central Atlantic which affected the Prebetic carbonate platform (South Iberian Continental Margin, northwestern margin of the Tethys) occurred. A graben morphology was developed in the platform coeval to a relative sea level fall. As a consequence, palustrine facies characterized by rhizoliths and some pond deposits of black lutites were established. Over these palustrine sediments, a second shallow carbonate platform was built during the early Albian. However, this process was not abrupt, as several levels with orbitolines and rudists were deposited intercalated between the continental facies, recording the transition to a new shallow marine carbonate platform developped during the Early Albian. The presence of these continental palustrine sediments between two episodes of shallow carbonate platform is described for the first time in the Prebetic. The demise of an upper Aptian isolated shallow carbonate platform drove to the deposition of these palustrine sediments in an extensional tectonic regime.
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Ajdanlijsky, George, Annette E. Götz e André Strasser. "The Early to Middle Triassic continental–marine transition of NW Bulgaria: sedimentology, palynology and sequence stratigraphy". Geologica Carpathica 69, n. 2 (1 aprile 2018): 129–48. http://dx.doi.org/10.1515/geoca-2018-0008.
Testo completoAbstract (sommario):
AbstractSedimentary facies and cycles of the Triassic continental–marine transition of NW Bulgaria are documented in detail from reference sections along the Iskar river gorge between the villages of Tserovo and Opletnya. The depositional environments evolved from anastomosing and meandering river systems in the Petrohan Terrigenous Group to mixed fluvial and tidal settings in the Svidol Formation, and to peritidal and shallow-marine conditions in the Opletnya Member of the Mogila Formation. For the first time, the palynostratigraphic data presented here allow for dating the transitional interval and for the precise identification of a major sequence boundary between the Petrohan Terrigenous Group and the Svidol Formation (Iskar Carbonate Group). This boundary most probably corresponds to the major sequence boundary Ol4 occurring in the upper Olenekian of the Tethyan realm and thus enables interregional correlation. The identification of regionally traceable sequence boundaries based on biostratigraphic age control is a first step towards a more accurate stratigraphic correlation and palaeogeographic interpretation of the Early to early Middle Triassic in NW Bulgaria.
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Sheldon, Nathan D., Stephen T. Grimes, Jerry J. Hooker, Margaret E. Collinson, Melanie J. Bugler, Michael T. Hren, Gregory D. Price e Paul A. Sutton. "Coupling of marine and continental oxygen isotope records during the Eocene-Oligocene transition". Geological Society of America Bulletin 128, n. 3-4 (14 settembre 2015): 502–10. http://dx.doi.org/10.1130/b31315.1.
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Olsen, Paul E., Dennis V. Kent e Jessica H. Whiteside. "Implications of the Newark Supergroup-based astrochronology and geomagnetic polarity time scale (Newark-APTS) for the tempo and mode of the early diversification of the Dinosauria". Earth and Environmental Science Transactions of the Royal Society of Edinburgh 101, n. 3-4 (settembre 2010): 201–29. http://dx.doi.org/10.1017/s1755691011020032.
Testo completoAbstract (sommario):
ABSTRACTThe Newark-APTS established a high-resolution framework for the Late Triassic and Early Jurassic. Palaeomagnetic polarity correlations to marine sections show that stage-level correlations of continental sequences were off by as much as 10 million years. New U–Pb ages show the new correlations and the Newark basin astrochronology to be accurate. Correlation of Newark-APTS to the Chinle Formation/Dockum Group, Glen Canyon Group, Fleming Fjord Formation and Ischigualasto Formation led to the following conclusions: (1) there are no unequivocal Carnian-age dinosaurs; (2) the Norian Age was characterised by a slowly increasing saurischian diversity but no unequivocal ornithischians; (3) there was profound Norian and Rhaetian continental provinciality; (4) the classic Chinle-, Germanic- and Los Colorados-type assemblages may have persisted to the close of the Rhaetian; (5) the distinct genus-level biotic transition traditionally correlated with the marine Carnian–Norian is in fact mid-Norian in age and within published error of the Manicouagan impact; (6) the end-Triassic marine and continental extinctions as seen in eastern North America were contemporaneous; and (7) compared to Triassic communities, Hettangian and Sinemurian age terrestrial communities were nearly globally homogenous and of low diversity. Consequently, the complex emerging picture of dinosaur diversification demands biostratigraphically-independent geochronologies in each of the faunally-important regions.
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Vilas-Boas, Margarida, Zélia Pereira, Simonetta Cirilli, Luís Vítor Duarte, Sérgio Luis Rodrigues Sêco e Paulo Fernandes. "Palynology and palynofacies studies in the lowermost Jurassic of the Lusitanian Basin (Pereiros Formation of the Silves Group), Portugal: evidence of the first transgressive episode". Acta Palaeobotanica 63, n. 2 (31 dicembre 2023): 129–50. http://dx.doi.org/10.35535/acpa-2023-0008.
Testo completoAbstract (sommario):
The Silves Group of the Lusitanian Basin in Portugal represents the initial infill of the continental rifting basins that formed during the breakup of northern Pangaea regions. Evaporites, especially halite, mark the transition from continental to marine settings and the beginning of the deposition in passive margin basins. This work presents the results of the palynostratigraphic and palynofacies analysis of two partial sections from the Pereiros Formation at the top of the Silves Group. The two sections are composed of sandstones, mudstones and dolostones interpreted as deposited in fluvial and lacustrine settings without apparent marine influence. The palynological content is diverse and wellpreserved, dating both sections to the early Hettangian (Lower Jurassic), indicated by the presence of spores Ischyosporites variegatus, Kraeuselisporites reissingeri, Porcellispora longdonensis and the pollen grains Perinopollenites elatoides and Pinuspollenites minimus. The palynological content of one of the sections (Lamas I) is noticeable by microforaminifera linings, suggesting evidence for a hitherto marine incursion at this age in the Silves Group stratigraphy. The beds that yielded the microforaminifera linings are interpreted as having been deposited in an estuarine-type setting, created by the first and short-lived marine transgressive event in the Lusitanian Basin during the early Hettangian.
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Domack, Eugene W., e P. T. Harris. "A new depositional model for ice shelves, based upon sediment cores from the Ross Sea and the MaC. Robertson shelf, Antarctica". Annals of Glaciology 27 (1998): 281–84. http://dx.doi.org/10.3189/1998aog27-1-281-284.
Testo completoAbstract (sommario):
We document the similarity of depositional facies occurring in gravity cores recovered from two disjunct regions of the Antarctic continental shelf: the Ross Sea and the MaC. Robertson shelf. The facies sequence model is represented in two cores, one collected during the 1995-1 cruise of the R/VNathaniel R. Palmer(core NBP95 TC-18) and the other collected by the RSVAurora Australisduring cruise 149 in 1995 (core 149 39GC38). Both cores show a succession of facies indicative of ice-shelf retreat during the late-Pleistocene to Holocene transition. Distinct lithofacies range in thickness from a few tens of cm to 1 m and consist of (from bottom to top) a coarse, granulated sandy mud; laminated silt and clay; structureless silly clay; poorly sorted sandy siliceous mud; and siliceous mud and ooze. These facies represent the passage of distinct depositional regimes across the core sites, including sub-ice shelf beneath a basal debris zone; sub-ice shell distal to a debris zone; calving-line transition; and open marine. This facies model represents an advance in our understanding of Glacial marine stratigraphy for the Antarctic continental shelf and will provide the basis for more realistic palaeoglacial reconstructions.
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SQUIER, ANGELA H., DOMINIC A. HODGSON e BRENDAN J. KEELY. "Evidence of late Quaternary environmental change in a continental east Antarctic lake from lacustrine sedimentary pigment distributions". Antarctic Science 17, n. 3 (17 agosto 2005): 361–76. http://dx.doi.org/10.1017/s0954102005002804.
Testo completoAbstract (sommario):
A sediment core from Progress Lake, one of the oldest lacustrine sequences in East Antarctica, contains distinct zones dating from a previous interglacial (most likely Marine Isotope Stage 5e, c. 125–115 kyr BP) and the present interglacial (Marine Isotope Stage 1), separated by a transition zone representing when the lake became sub-glacial. Profiles of fossil pigments, determined using high performance liquid chromatography and liquid chromatography-tandem mass spectrometry, show distinct differences in the photoautotrophic community during these two interglacial periods. The first was dominated by algae and purple phototrophic bacteria, with periods of photic zone euxinia indicated by pigments from anoxygenic phototrophic bacteria. Specific chlorophyll a derivatives reveal periods when grazing pressure impacted significantly on the phytoplankton community. The virtual absence of pigments in the transition zone reflects severe restriction of photoautotrophic activity, consistent with the lake having become sub-glacial. Retreat of snow and ice in the late Holocene (3345 14C yr BP) allowed establishment of a less diverse primary producer community, restricted to algae and cyanobacteria. Grazers were severely restricted and oxidative transformation was more important than during the previous interglacial. The pigment data provide a unique and detailed insight in to the evolution of the lake ecology over an interglacial-glacial-interglacial transition and strong evidence that the Marine Isotope Stage 5e interglacial in this region of coastal East Antarctica was several degrees warmer than at present.
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Cortés Sánchez, Miguel, Francisco J. Jiménez Espejo, María D. Simón Vallejo, Juan F. Gibaja Bao, António Faustino Carvalho, Francisca Martinez-Ruiz, Marta Rodrigo Gamiz et al. "The Mesolithic–Neolithic transition in southern Iberia". Quaternary Research 77, n. 2 (marzo 2012): 221–34. http://dx.doi.org/10.1016/j.yqres.2011.12.003.
Testo completoAbstract (sommario):
New data and a review of historiographic information from Neolithic sites of the Malaga and Algarve coasts (southern Iberian Peninsula) and from the Maghreb (North Africa) reveal the existence of a Neolithic settlement at least from 7.5 cal ka BP. The agricultural and pastoralist food producing economy of that population rapidly replaced the coastal economies of the Mesolithic populations. The timing of this population and economic turnover coincided with major changes in the continental and marine ecosystems, including upwelling intensity, sea-level changes and increased aridity in the Sahara and along the Iberian coast. These changes likely impacted the subsistence strategies of the Mesolithic populations along the Iberian seascapes and resulted in abandonments manifested as sedimentary hiatuses in some areas during the Mesolithic–Neolithic transition. The rapid expansion and area of dispersal of the early Neolithic traits suggest the use of marine technology. Different evidences for a Maghrebian origin for the first colonists have been summarized. The recognition of an early North-African Neolithic influence in Southern Iberia and the Maghreb is vital for understanding the appearance and development of the Neolithic in Western Europe. Our review suggests links between climate change, resource allocation, and population turnover.
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Zhang, Jizhen, Wei Lin, Mingtao Li, Jianguo Wang, Xiao Xiao, Yu Li e Xiaochan Zhang. "Evolution Mechanism of Microscopic Pore System in Coal-Bearing Marine–Continental Transitional Shale with Increasing Maturation". Minerals 13, n. 12 (24 novembre 2023): 1482. http://dx.doi.org/10.3390/min13121482.
Testo completoAbstract (sommario):
The formation and evolution mechanisms of complex types and scales of marine–continental transitional shale pores are still indefinite, restricting the accurate evaluation of shale reservoir and the effective evaluation of coal-bearing marine–continental transitional shale gas resource quantity. Considering the Shanxi shale in Ordos basin of China as the research object, combining the FE-SEM images and petrophysical analysis, high-pressure mercury intrusion porosimetry, and CO2 and N2 adsorption–desorption experiments, the structure characteristics and differential evolution mechanisms of multiscale and multitype of coal-bearing shale pores were discussed. The results show that coal-bearing marine–continental transitional shales are rich in clay minerals and organic matters (OMs). Pores developed within organic matters, clay, and brittle minerals of coal-bearing shale have decreasing porosity values. OM pores are directly related to micro- and mesopores, with high specific surface areas, while the porosity of inorganic pores increases with the increasing pore diameter. The porosity of all pores shows a positive relationship with permeability, which changes periodically with the increase in maturity. Coal-bearing shale pores are mainly plate- and ink bottle-shaped, with multimodal pore size distributions. Controlled by both diagenesis and hydrocarbon generation, the evolution of coal-bearing shale pores could be mainly divided into four stages. Furthermore, the pore evolution model of coal-bearing marine–continental transitional shale was preliminarily constructed. This study would enhance the understanding of reservoir evolution of the coal-bearing shale and provide useful information for the assessment and evaluation of reservoir capacity.
24
Deconinck, J. F., A. Strasser e P. Debrabant. "Formation of illitic minerals at surface temperatures in Purbeckian sediments (Lower Berriasian, Swiss and French Jura)". Clay Minerals 23, n. 1 (marzo 1988): 91–103. http://dx.doi.org/10.1180/claymin.1988.023.1.09.
Testo completoAbstract (sommario):
AbstractThe clay-mineralogical assemblages of Purbeckian carbonate sediments of the Swiss and French Jura Mountains are often composed of illite and interstratified illite-smectite. These illitic minerals occur mainly in thin layers of green marls which show evidence of subaerial exposure and mark the top of shallowing-upward sequences. X-ray diffraction, chemical and thermal analyses coupled with transmission electron microscopy suggest that the Purbeckian illitic minerals replaced smectite in intermediate continental-marine environments. The transition from smectite to illite and interstratified illite-smectite probably resulted from repeated cycles of wetting by marine waters and subsequent drying in hypersaline environments, under a hot Purbeckian climate.
25
Chi Fru, Ernest, Nathalie P. Rodríguez, Camille A. Partin, Stefan V. Lalonde, Per Andersson, Dominik J. Weiss, Abderrazak El Albani, Ilia Rodushkin e Kurt O. Konhauser. "Cu isotopes in marine black shales record the Great Oxidation Event". Proceedings of the National Academy of Sciences 113, n. 18 (18 aprile 2016): 4941–46. http://dx.doi.org/10.1073/pnas.1523544113.
Testo completoAbstract (sommario):
The oxygenation of the atmosphere ∼2.45–2.32 billion years ago (Ga) is one of the most significant geological events to have affected Earth’s redox history. Our understanding of the timing and processes surrounding this key transition is largely dependent on the development of redox-sensitive proxies, many of which remain unexplored. Here we report a shift from negative to positive copper isotopic compositions (δ65CuERM-AE633) in organic carbon-rich shales spanning the period 2.66–2.08 Ga. We suggest that, before 2.3 Ga, a muted oxidative supply of weathering-derived copper enriched in 65Cu, along with the preferential removal of 65Cu by iron oxides, left seawater and marine biomass depleted in 65Cu but enriched in 63Cu. As banded iron formation deposition waned and continentally sourced Cu became more important, biomass sampled a dissolved Cu reservoir that was progressively less fractionated relative to the continental pool. This evolution toward heavy δ65Cu values coincides with a shift to negative sedimentary δ56Fe values and increased marine sulfate after the Great Oxidation Event (GOE), and is traceable through Phanerozoic shales to modern marine settings, where marine dissolved and sedimentary δ65Cu values are universally positive. Our finding of an important shift in sedimentary Cu isotope compositions across the GOE provides new insights into the Precambrian marine cycling of this critical micronutrient, and demonstrates the proxy potential for sedimentary Cu isotope compositions in the study of biogeochemical cycles and oceanic redox balance in the past.
26
DELMER, André, Michiel DUSAR e Bernard DELCAMBRE. "Upper Carboniferous lithostratigraphic units (Belgium)". Geologica Belgica 4, n. 1-2 (15 aprile 2002): 95–103. http://dx.doi.org/10.20341/gb.2014.045.
Testo completoAbstract (sommario):
Upper Carboniferous, Namurian to Westphalian coal measures in Belgium form part of the Variscan Foredeep in northwestern Europe, with maximum preserved thickness over 3500 m. Despite post-depositional separation of the Wallonian and Campine coal basins by the Brabant Massif and different tectonic styles, a common lithostratigraphic nomenclature can be applied. The stratigraphic subdivision is based on the distinction between a carbonate-dominated marine "Dinantian" and siliciclastic continental, coal-bearing "Silesian". Basal units testify of a marine transgression, locally continuous with Dinantian carbonate sedimentation, elsewhere drowning an emergent karst landscape. Progressive advance and uplift of the Variscan orogenic belt caused rapid subsidence in the foreland and transition from prodelta mudstones to upper alluvial plain conglomerates, with fewer marine incursions. The Belgian Coal Measures Group encompasses this complete tectonically-driven sedimentary succession.
27
Lézine, Anne-Marie, Franck Bassinot e Jean-Yves Peterschmitt. "Orbitally-induced changes of the Atlantic and Indian monsoons over the past 20,000 years: New insights based on the comparison of continental and marine records". Bulletin de la Société Géologique de France 185, n. 1 (1 gennaio 2014): 3–12. http://dx.doi.org/10.2113/gssgfbull.185.1.3.
Testo completoAbstract (sommario):
Abstract Variations of Atlantic and Indian monsoon systems since the last glacial period are investigated by comparing eolian fluxes from two marine cores (ODP site 658 off western Africa and core 74KL off the Arabian peninsula) with 2147 hydrological records (lacustrine, palustrine, spring and fluvial, arid) gathered over a large continental area extending between 10 and 30°N across Africa, Arabia and western India. We show that the hydrological response to the Holocene humid phase in the northern tropics strongly differs from a region to another. The humid period is significantly shorter in the Arabian peninsula and the horn of Africa compared to northern Africa even though its maximum is contemporaneous (11,000–7,000 cal yr BP). Western India displays a specific hydrological signal characterized by the importance of well-developed fluvial systems from the Himalayas and the paucity of lakes compared to the other regions. In western India, the humid peak is shifted toward the mid Holocene (8,000–6,000 cal yr BP). Both marine records show a peak between ~ 11,000 and 7,000 cal yr BP for the Holocene humid period, in good accordance with African-Arabian records. However, while continental hydrological data suggest that the onset and termination of this humid period might have been relatively progressive, the marine windborne records indicate abrupt transitions, somewhat out-of-phase with continental evidence (e.g. abrupt decrease of aeolian proxies as early as ~ 15,000 cal yr BP). Discrepancies between marine and continental likely result from the fact that aeolian fluxes at a given marine location do not simply record monsoon-related changes of humidity over the adjacent continental sources but could be affected also by changes of the source area (e.g., emersion of the Arabo-Persian gulf associated to the glacial, low sea-level stand), and changes in wind intensity and/or direction.
28
Szameitat, Luizemara Soares Alves, Francisco José Fonseca Ferreira, Gianreto Manatschal e Monica da Costa Pereira Lavalle Helbron. "EVIDENCE OF MANTLE INHERITANCE ON THE ULTRA-DISTAL WESTERN IBERIAN MARGIN FROM TRANSFORMED TOTAL MAGNETIC ANOMALY". Revista Brasileira de Geofísica 36, n. 3 (6 settembre 2018): 1. http://dx.doi.org/10.22564/rbgf.v36i3.1957.
Testo completoAbstract (sommario):
ABSTRACT. Inheritance on continental lithosphere is considered as an important aspect on passive margins, since they may control magmatic budget and strain evolution during rifting and lithospheric breakup. On the distal Western Iberian margin, the transition to a steady state oceanic crust was little sampled and less investigated, in comparison to the more proximal parts near to the continental edge. In this work, we use marine magnetic data to analyze some aspects of the transition between the zone of exhumed continental mantle (ZECM) and the unequivocal oceanic crust, using transformed magnetic data. We observe that the end of the ZECM presents some straight magnetic features, especially at the eastern limit of the J anomaly. These magnetic lineaments are consistent with Early Cretaceous flow lines of the Iberian Plate. Straight structures are not expected in a newly formed oceanic lithosphere. Instead, it seems to be controlled by mantle inheritance. These straight magnetic features may indicate basement inheritance controlling magmatic insertions at the beginning of the oceanic crust formation.Keywords: Iberia, Magnetometry, Ocean-Continent Transition, Inherited Structures, Magma-Poor Margin. RESUMO. Estruturas herdadas na litosfera continental são um aspecto importante em margens passivas, pois poderão condicionar a entrada de magma e a evolução da deformação durante o rifteamento e quebra litosférica. Na porção distal da Margem Ibérica Ocidental, a transição da crosta continental até a crosta oceânica bem estabelecida possui menos dados e é menos investigada em comparação com a porção junto do limite de crosta continental. Neste trabalho, usamos dados magnéticos marinhos para analisar alguns aspectos entre a zona de exumação mantélica e a crosta oceânica inequívoca, através de dados magnéticos transformados. Observa-se que o final da zona de exumação mantélica apresenta algumas feições retilíneas, especialmente no limite leste da Anomalia J. Estes lineamentos magnéticos estão em conformidade com linhas de fluxo mesozoicas da Placa Ibérica. Feições retilíneas não são esperadas em uma litosfera oceânica neoformada. Ao contrário, estas aparentam ser um controle dado por estruturas pretéritas do manto. Portanto, estas feições magnéticas retilíneas sugerem uma herança do embasamento continental controlando as intrusões magmáticas no início da formação da crosta oceânica.Palavras-chave: Ibéria, Magnetometria, Transição Continente-Oceano, Estruturas Herdadas, Margem Pobre em Magma.
29
Smith, D. B., J. C. M. Taylor, R. S. Arthurton, M. E. Brookfield e K. W. Glennie. "Permian". Geological Society, London, Memoirs 13, n. 1 (1992): 87–96. http://dx.doi.org/10.1144/gsl.mem.1992.013.01.10.
Testo completoAbstract (sommario):
AbstractPermian strata in the British Isles crop out mainly in northern and central England but are extensive in the subsurface both on land and in several adjoining offshore areas. Their base is defined as in Smith et al. (1974) and their top is within red beds, overlying the Zechstein evaporites.We emphasize that both the base and the top of the nominally Permian rocks lie in continental strata almost devoid of stratigraphically useful fossils and that, accordingly, these boundaries are only doubtfully correlated with internationally acceptable biostratigraphic standards.Subdivision of British Permian strata into Lower and Upper series follows the traditional view summarized by Smith et al. (1974). The junction between the series is taken at the incoming of marine strata in northern England and adjoining offshore areas, and at approximately equivalent levels in continuous continental sequences elsewhere; recent limited palynological studies suggest that the early Permian-late Permian transition adopted here and in most of northwest Europe may be mid or late Kazanian or even Tatarian in age which is somewhat younger than the base-Kazanian/Ufimian position taken in more continuous marine sequences.There has been no comprehensive revision of the stratigraphy and nomenclature of early Permian strata in and around the British Isles since the work of Smith et al. (1974) and Rhys (1974), but these aspects of the early Permian continental deposits of several cuvettes and inland drainage basins in southwest Scotland were reviewed by Brookfield (1978) and the age of continental deposits in the Elgin area was reconsidered
30
Jiao, Pengfei, Genshun Yao, Shangwen Zhou, Zhe Yu e Shiluo Wang. "A Comparative Study of the Micropore Structure between the Transitional and Marine Shales in China". Geofluids 2021 (7 aprile 2021): 1–14. http://dx.doi.org/10.1155/2021/5562532.
Testo completoAbstract (sommario):
To compare the micropore structure of marine-continental transitional shale with marine shale, organic geochemical, field emission scanning electron microscopy, and low-temperature nitrogen adsorption experiments were conducted on shale samples from the Shanxi Formation in the eastern Ordos Basin and the Longmaxi Formation in the southern Sichuan Basin. The results show that Shanxi Formation shale has a smaller specific surface area and pore volume than Longmaxi Formation shale; therefore, the transitional shales fail to provide sufficient pore spaces for the effective storage and preservation of natural gas. Both the transitional and marine shales are in an overmature stage with high total organic carbon content, but they differ considerably in pore types and development degrees. Inorganic pores and fractures are dominantly developed in transitional shales, such as intragranular pores and clay mineral interlayer fractures, while organic nanopores are rarely developed. In contrast, organic pores are the dominant pore type in the marine shales and inorganic pores are rarely observed. The fractal analysis also shows that pore structure complexity and heterogeneity are quite different. These differences were related to different organic types, i.e., type I of marine shale and type III of transitional shale. Marine Longmaxi shale has experienced liquid hydrocarbon cracking, gas generation, and pore-forming processes, providing good conditions for natural gas to be preserved. However, during the evolution of transitional Shanxi shale, gas cannot be effectively preserved due to the lack of the above evolution processes, leading to the poor gas-bearing property. The detailed comparison of the micropore structure between the transitional and marine shales is of great importance for the future exploitation of marine-continental transitional shale gas in China.
31
Nittrouer, Charles A., David J. DeMaster, Steven A. Kuehl, Alberto G. Figueiredo, Richard W. Sternberg, L. Ercilio C. Faria, Odete M. Silveira et al. "Amazon Sediment Transport and Accumulation Along the Continuum of Mixed Fluvial and Marine Processes". Annual Review of Marine Science 13, n. 1 (3 gennaio 2021): 501–36. http://dx.doi.org/10.1146/annurev-marine-010816-060457.
Testo completoAbstract (sommario):
Sediment transfer from land to ocean begins in coastal settings and, for large rivers such as the Amazon, has dramatic impacts over thousands of kilometers covering diverse environmental conditions. In the relatively natural Amazon tidal river, combinations of fluvial and marine processes transition toward the ocean, affecting the transport and accumulation of sediment in floodplains and tributary mouths. The enormous discharge of Amazon fresh water causes estuarine processes to occur on the continental shelf, where much sediment accumulation creates a large clinoform structure and where additional sediment accumulates along its shoreward boundary in tidal flats and mangrove forests. Some remaining Amazon sediment is transported beyond the region near the river mouth, and fluvial forces on it diminish. Numerous perturbations to Amazon sediment transport and accumulation occur naturally, but human actions will likely dominate future change, and now is the time to document, understand, and mitigate their impacts.
32
Herrero-Hernández, Antonio, Fernando Gómez-Fernández e Francisco Javier López-Moro. "Upper Cretaceous marine-continental transition (Leonese Area, NW Spain) defined from integrated outcrop and seismic stratigraphy". Geological Journal 50, n. 1 (8 agosto 2013): 39–55. http://dx.doi.org/10.1002/gj.2525.
Testo completo
33
Stori, L., J. B. Diez, M. Juncal, R. De la Horra, V. Borruel-Abadía, J. Martín-Chivelet, J. F. Barrenechea, J. López-Gómez e A. Ronchi. "The Anisian continental-marine transition in Sardinia (Italy): state of the art, new palynological data and regional chronostratigraphic correlation". Journal of Iberian Geology 48, n. 1 (16 febbraio 2022): 79–106. http://dx.doi.org/10.1007/s41513-021-00184-x.
Testo completoAbstract (sommario):
AbstractThe scarce evidence of paleontological records between the upper Permian and the Anisian (Middle Triassic) of Western Europe could reflect (1) large stratigraphic gaps in the continental successions and/or (2) the persistence of disturbed conditions after the Permian–Triassic Boundary extinction event and the succession of ecological crises that occurred during the Early Triassic. In this context, the study of palynological associations, integrated with the stratigraphical and sedimentological data, plays a key role in dating and correlating the successions of the Western European domain and improves our understanding of environmental and paleoclimatic conditions. In some cases, pre-Anisian paleontological evidence is lacking, as in Sardinia (Italy), where a long gap encompasses the middle Permian (pars) to late Lower Triassic successions. Although fragmented and disseminated, the continental Lower-Middle Triassic sedimentary successions (Buntsandstein) of Sardinia have proved crucial to our understanding of the evolution of the southern edge of the Paleo-Europe and the different timings of the Tethys transgression (Muschelkalk facies) in some of these areas. Various paleogeographic reconstructions were attempted in previous works, without providing any consensus on the precise position of Sardinia and its surrounding seaways in the Western Tethys domain during this time interval. At present, the configuration and distribution of the subsiding and emerging landmasses and the temporal development of the transgressions of the Western Tethys during the Middle Triassic remain unclear. This work focuses on the stratigraphical, sedimentological and palynological aspects of three Middle Triassic continental-marine sedimentary successions in Sardinia, with particular attention to the analysis of the palynological associations sampled there, and it also provides a detailed review of all previous palynological publications on the Sardinian Anisian. The studied successions are: Su Passu Malu section (Campumari, SW Sardinia), Arcu is Fronestas section and Escalaplano section (Escalaplano, Central Sardinia). These sections were also correlated to other significant sections in the SW (Scivu Is Arenas) and NW (Nurra) parts of the island.
34
Occhietti, Serge, Sanda Balescu, Michel Lamothe, Martine Clet, Thomas Cronin, Pierre Ferland e Pierre Pichet. "Late Stage 5 Glacio-isostatic Sea in the St. Lawrence Valley, Canada and United States". Quaternary Research 45, n. 2 (marzo 1996): 128–37. http://dx.doi.org/10.1006/qres.1996.0015.
Testo completoAbstract (sommario):
AbstractAlthough post-glacial marine sediments of late Wisconsinan and early Holocene age are common in eastern Canada and the northeastern United States, remnants of older Pleistocene marine sediments are scarce. A fossiliferous marine clay that predates the classical Wisconsinan was recently discovered in the St. Lawrence Valley. A dominantly estuarine environment is inferred from the geochemistry of the shells (δ18O = −7.1) and from benthic foraminifer and ostracode assemblages. The clay indicates a marine invasion (Cartier Sea) shallower and probably shorter than that during the upper late Wisconsinan Champlain Sea episode (12,000–9,500 yr B.P.). The pollen content shows that regional vegetation during the marine episode began as open tundra, then became a Betula and Alnus crispa forest, reached a climatic optimum with Quercus, Corylus, and Abies, and concluded as a Pinus/Picea boreal forest. A corrected infrared stimulated luminescence age of 98,000 ± 9000 yr is compatible with the epimerization ratio of shells. The Cartier Sea resulted from a post-glacial glacio-isostatic marine invasion in the St. Lawrence lowlands. It probably occurred during late stage 5 and is tentatively assigned to the transition of oxygen isotope substages 5b/5a. This marine episode dates to stage 5 of the preceding continental glacier which extended to middle latitudes in NE America.
35
Zhang, Manting, Mingyi Hu, Quansheng Cai, Qingjie Deng, Sile Wei, Kai Wang, Yuqian Li e Ye Han. "Controlling Factors of Organic Matter Enrichment in Marine–Continental Transitional Shale: A Case Study of the Upper Permian Longtan Formation, Northern Guizhou, China". Minerals 14, n. 6 (24 maggio 2024): 540. http://dx.doi.org/10.3390/min14060540.
Testo completoAbstract (sommario):
The marine–continental transitional shale of the Upper Permian Longtan Formation in northern Guizhou is an important source rock in the upper Yangtze region of China, and it holds significant potential for the exploration of shale gas. To investigate the correlation between sedimentary conditions and the accumulation of organic matters in marine–continental transitional shale, this paper performed an extensive analysis using organic geochemical testing, organic petrology examination, a cross-section polisher–scanning electron microscope (CP-SEM), and geochemical analysis. The Jinsha and Dafang drilling cores were selected as the research subjects. The results showed that the TOC of the Longtan Formation in the study area was relatively high, and the TOC content of the tidal flat–lagoon environment (average of 8.37%) was significantly higher than that of the delta samples (average of 2.77%). The high content of Al2O3 (average of 17.41% in DC-1, average of 16.53% in JC-1) indicated strong terrigenous detrital input. The proxies indicated that the Longtan Formation shale in northern Guizhou was deposited in a climate that was both warm and humid, with oxic–dysoxic sedimentary water characterized by high biological productivity and a rapid sedimentation rate. The organic-rich shales during the marine and continental transitional phases were affected by various factors, including the paleo-climate, water redox properties, paleo-productivity, sedimentation rate, and other variables, which directly or indirectly impacted the availability, burial, and preservation of organic matter.
36
Zhang, Bing, Siyu Wen, Kai Yang, Kai Ma, Pengwan Wang, Chuan Xu e Gaoquan Cao. "Diagenetic Evolution Sequence and Pore Evolution Characteristics: Study on Marine-Continental Transitional Facies Shale in Southeastern Sichuan Basin". Minerals 13, n. 11 (18 novembre 2023): 1451. http://dx.doi.org/10.3390/min13111451.
Testo completoAbstract (sommario):
Diagenesis and pore structure are essential factors for reservoir evaluation. marine-continental transitional facies shale is a new shale gas reservoir of concern in the Sichuan Basin. The research on its diagenesis pore evolution model has important guiding significance in its later exploration and development. However, the current research on pore structure changes, diagenesis, and the evolution of marine-continental transitional facies shale is not sufficient and systematic. In order to reveal the internal relationship between pore structure changes and diagenesis, the evolution of marine-continental transitional facies shale was tested by X-ray diffraction, field emission scanning electron microscopy, low-pressure gas adsorption, nuclear magnetic resonance, and the diagenetic evolution sequence and nanopore system evolution of Longtan Formation shale was systematically studied. The results show that the Longtan Formation shale underwent short-term shallow after sedimentation, followed by long-term deep burial. The main diagenetic mechanisms of the Longtan Formation shale include compaction, dissolution, cementation, thermal maturation of organic matter, and transformation of clay minerals, which are generally in the middle-late diagenetic stage. The pore structure undergoes significant changes with increasing maturity, with the pore volumes of both micropores and mesopores reaching their minimum values at Ro = 1.43% and subsequently increasing. The change process of a specific surface area is similar to that of pore volumes. Finally, the diagenetic pore evolution model of Longtan Formation MCFS in Southeastern Sichuan was established.
37
Sabin, Ann L., e Nicklas G. Pisias. "Sea Surface Temperature Changes in the Northeastern Pacific Ocean during the Past 20,000 Years and Their Relationship to Climate Change in Northwestern North America". Quaternary Research 46, n. 1 (luglio 1996): 48–61. http://dx.doi.org/10.1006/qres.1996.0043.
Testo completoAbstract (sommario):
Modern ocean–atmosphere interactions in the northeastern Pacific Ocean have a significant effect on the climate of the west coast of North America. We present radiolarian microfossil-based temperature reconstructions for the eastern North Pacific spanning the past 20,000 yr to examine possible correlations and linkages between continental climate change and changes in sea surface temperature (SST) in the northeastern Pacific Ocean on millennial time scales. The reconstructions indicate that the regional pattern of ocean circulation off the west coast of North America was further south 15,000 cal yr B.P. than it is today, and reached its present location 13,000 cal yr B.P. The North Pacific Drift and Transition Zone were further south as a result of a more southerly North Pacific high pressure cell prior to 13,000 cal yr B.P. While two continental paleoclimate records from northwestern North America show regional differences, they also can be correlated to the SST changes. A coastal site at 48°N shows similar patterns in summer temperatures, as observed in offshore marine records of SSTs. However, an inland continental record seems to reflect more-regional-scale changes in sea surface conditions showing a thermal maximum centered at 10,000 cal yr B.P which is observed in the marine transect south of 42°N. We conclude, based on the pattern of oceanographic change as reflected in radiolarian assemblages, that changes in the past latitudinal position of the North Pacific Drift played a significant role in controlling continental climate immediately to its east, as it does in the present environment. We also conclude that during the past 20,000 yr much of the evolution of oceanographic change is related to the migration of the atmospheric pressure cells (the North Pacific high and Aleutian low) of the northeastern Pacific.
38
Ramos, Amparo. "Transition from alluvial to coastal deposits (Permian–Triassic) on the Island of Mallorca, western Mediterranean". Geological Magazine 132, n. 4 (luglio 1995): 435–47. http://dx.doi.org/10.1017/s001675680002149x.
Testo completoAbstract (sommario):
AbstractNon-marine redbeds (Permian and Triassic) in the island of Mallorca consist of a 0.4 km-thick alluvial succession that passes upwards into siliciclastic–carbonate coastal deposits. Tectonics and sealevel changes have been the main influences in their evolution. Low in this succession (the ‘Areniscas y lutitas de Port des Canonge’ unit) sandstone sheets with lateral accretion surfaces (macroscale inclined strata) and mudstones with frequent exposure structures are interpreted as the products of a sinuous alluvial system and floodplain. Climatic fluctuations are considered to be responsible for some significant up-section changes in the evolution of the alluvial deposits. Low-angle or horizontally stratified sandy units, interpreted as the result of flash floods, alternate upwards with point-bar deposits in the ‘Areniscas de Asá’. The hydrological response to minor climatic changes was evidently nearly instantaneous due to the lack of significant vegetation cover.During accumulation of mudstones and sandstones of the overlying ‘Lutitas y Areniscas de Son Serralta’ unit, the interpreted environment of deposition changed from a distal braidplain, mainly constructed by superposition of sandy bedforms with straight or linguoid crestlines in low sinuosity river channels, into a coastal plain with evidence of both continental and marine influences. The overlying carbonate platform (Muschelkalk) marks the development of a more homogeneous marine environment resulting from the Tethyan transgressive event that affected the whole peri-Mediterranean realm during the Anisian (middle Triassic).
39
Ng, Christiano, Cristina Silveira Vega e Maria da Saudade Araujo Santos Maranhão. "Mixed carbonate-siliciclastic microfacies from Permian deposits of Western Gondwana: Evidence of gradual marine to continental transition or episodes of marine transgression?" Sedimentary Geology 390 (luglio 2019): 62–82. http://dx.doi.org/10.1016/j.sedgeo.2019.07.006.
Testo completo
40
WELCOMME, JEAN-LOUP, MOULOUD BENAMMI, JEAN-YVES CROCHET, LAURENT MARIVAUX, GRÉGOIRE MÉTAIS, PIERRE-OLIVIER ANTOINE e IBRAHIM BALOCH. "Himalayan Forelands: palaeontological evidence for Oligocene detrital deposits in the Bugti Hills (Balochistan, Pakistan)". Geological Magazine 138, n. 4 (luglio 2001): 397–405. http://dx.doi.org/10.1017/s0016756801005428.
Testo completoAbstract (sommario):
In the southwestern Sulaiman geological province (Balochistan, Pakistan), terrestrial detrital facies from the Bugti Hills region have yielded the richest Tertiary vertebrate faunas to be found in Asia thus far. New fossils from five successive and distinct ‘bone beds’ bridge the supposed Oligocene sedimentary hiatus within the Sulaiman geological province; the lowermost continental levels of the previously described Miocene Chitarwata Formation, known as the Bugti Member, are Oligocene in age in the Bugti area. Neither a mixture of heterochronic faunal elements nor endemism of any fauna is evident in this area. Additional microfaunal material from the Bugti Member constrains an Oligocene age for the lower Chitarwata Formation in Zinda Pir (northeast of the Bugti Hills). This Oligocene transition between the marine Kirthar (Eocene) and continental Siwalik (Miocene) deposits consists of a regressive fluvio-deltaic system occupying a vast floodplain. It represents an early-stage molasse in the palaeo-Indus Basin which drained western orogenic highlands resulting from the collision between the Indian and Eurasian plates.
41
Komarov, V. N., e S. A. Samokhvalov. "On the textbook “Genetic analysis of terrigenous deposits”". Proceedings of higher educational establishments. Geology and Exploration, n. 3 (22 novembre 2022): 94–98. http://dx.doi.org/10.32454/0016-7762-2022-64-3-94-98.
Testo completoAbstract (sommario):
The textbook under review considers the fundamentals of the genetic analysis of terrigenous and associated sediments. A classification scheme of the genetic types, subgroups, groups, and supergroups of these deposits is provided. According to the proposed scheme, continental, transitional, marine, and mixed genetic types are sequentially described. A set of sedimentation features that allow for identification of the genetic type, its lateral and vertical transitions to other genetic types, is introduced. The form and size of modern accumulative bodies formed by genetic types of deposits and their fossil analogues are indicated.
42
Filipescu, Sorin, Angela Miclea, Martin Gross, Mathias Harzhauser, Kamil Zágoršek e Cătălin Jipa. "Early Sarmatian paleoenvironments in the easternmost Pannonian Basin (Borod Depression, Romania) revealed by the micropaleontological data". Geologica Carpathica 65, n. 1 (1 febbraio 2014): 67–81. http://dx.doi.org/10.2478/geoca-2014-0005.
Testo completoAbstract (sommario):
Abstract The Sarmatian sedimentary record of the Borod Depression (eastern Pannonian Basin) consists of a marine sequence with continental influence. The investigated section, located near Vârciorog, was biostratigraphically and paleoenvironmentally analysed. The micro- and macrofossil assemblages include dasycladaceans, characeans, foraminifera, molluscs, polychaetes, ostracods, crabs, bryozoans, fish and vertebrate remains, which are characteristic for a shallow marine setting with local transitions to continental facies. The microfossil assemblages are characteristic for the Elphidium reginum Zone and Mohrensternia Zone of the early Sarmatian (Serravallian). The succession of populations correlates with the sedimentological trend, allowing the separation of several genetic units. The relative sea-level changes and the progradational trend from the top of the section suggest active tectonics in the hinterland (Apuseni Mountains). The shallow seas surrounding the emerging islands (Apuseni Mountains) provided the connections between the Pannonian and Transylvanian basins during the early Sarmatian
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Sutter, Johannes, Hubertus Fischer, Klaus Grosfeld, Nanna B. Karlsson, Thomas Kleiner, Brice Van Liefferinge e Olaf Eisen. "Modelling the Antarctic Ice Sheet across the mid-Pleistocene transition – implications for Oldest Ice". Cryosphere 13, n. 7 (19 luglio 2019): 2023–41. http://dx.doi.org/10.5194/tc-13-2023-2019.
Testo completoAbstract (sommario):
Abstract. The international endeavour to retrieve a continuous ice core, which spans the middle Pleistocene climate transition ca. 1.2–0.9 Myr ago, encompasses a multitude of field and model-based pre-site surveys. We expand on the current efforts to locate a suitable drilling site for the oldest Antarctic ice core by means of 3-D continental ice-sheet modelling. To this end, we present an ensemble of ice-sheet simulations spanning the last 2 Myr, employing transient boundary conditions derived from climate modelling and climate proxy records. We discuss the imprint of changing climate conditions, sea level and geothermal heat flux on the ice thickness, and basal conditions around previously identified sites with continuous records of old ice. Our modelling results show a range of configurational ice-sheet changes across the middle Pleistocene transition, suggesting a potential shift of the West Antarctic Ice Sheet to a marine-based configuration. Despite the middle Pleistocene climate reorganisation and associated ice-dynamic changes, we identify several regions conducive to conditions maintaining 1.5 Myr (million years) old ice, particularly around Dome Fuji, Dome C and Ridge B, which is in agreement with previous studies. This finding strengthens the notion that continuous records with such old ice do exist in previously identified regions, while we are also providing a dynamic continental ice-sheet context.
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OLIVIER, NICOLAS, ARNAUD BRAYARD, EMMANUEL FARA, KEVIN G. BYLUND, JAMES F. JENKS, EMMANUELLE VENNIN, DANIEL A. STEPHEN e GILLES ESCARGUEL. "Smithian shoreline migrations and depositional settings in Timpoweap Canyon (Early Triassic, Utah, USA)". Geological Magazine 151, n. 5 (17 gennaio 2014): 938–55. http://dx.doi.org/10.1017/s0016756813000988.
Testo completoAbstract (sommario):
AbstractIn Timpoweap Canyon near Hurricane (Utah, USA), spectacular outcrop conditions of Early Triassic rocks document the geometric relationships between a massive Smithian fenestral-microbial unit and underlying, lateral and overlying sedimentary units. This allows us to reconstruct the evolution of depositional environments and high-frequency relative sea-level fluctuations in the studied area. Depositional environments evolved from a coastal plain with continental deposits to peritidal settings with fenestral-microbial limestones, which are overlain by intertidal to shallow subtidal marine bioclastic limestones. This transgressive trend of a large-scale depositional sequence marks a long-term sea-level rise that is identified worldwide after the Permian–Triassic boundary. The fenestral-microbial sediments were deposited at the transition between continental settings (with terrigenous deposits) and shallow subtidal marine environments (with bioturbated and bioclastic limestones). Such a lateral zonation questions the interpretation of microbial deposits as anachronistic and disaster facies in the western USA basin. The depositional setting may have triggered the distribution of microbial deposits and contemporaneous marine biota. The fenestral-microbial unit is truncated by an erosional surface reflecting a drop in relative sea level at the scale of a medium depositional sequence. The local inherited topography allowed the recording of small-scale sequences characterized by clinoforms and short-distance lateral facies changes. Stratal stacking pattern and surface geometries allow the reconstruction of relative sea-level fluctuations and tracking of shoreline migrations. The stacking pattern of these small-scale sequences and the amplitude of corresponding high-frequency sea-level fluctuations are consistent with climatic control. Large- and medium-scale sequences suggest a regional tectonic control.
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Musa, Ojochenemi K., Ewa E. Kurowska, Tomasz Krzykawski e Jimoh A. Onimisi. "X-ray diffraction studies of onshore mud volcanoes in parts of the Upper Benue Trough, northeastern Nigeria". Geology, Geophysics and Environment 47, n. 4 (30 dicembre 2021): 203–16. http://dx.doi.org/10.7494/geol.2021.47.4.203.
Testo completoAbstract (sommario):
The mineralogical studies of clay from the onshore mud volcanoes discovered in parts of the Upper Benue Trough of Nigeria provide a clue about the geological formation from which the extruded mud originates. The study area is a part of the Cretaceous Upper Benue Trough filled with Early Cretaceous continental deposits and Late Cretaceous marine deposits, having a history of magmatism dating from the Albian to the Pleistocene. The study approach involves integrated inorganic geochemical analysis of the samples to reveal their composition and origin. The results of XRD analysis of the fresh clays from the mud volcano revealed the presence of quartz, kaolinite, and other clay minerals (illite-smectite), feldspars, and in much lower quantities, other accessory minerals including muscovite, evaporites, calcite and dolomite, trona, barite, goethite. The saprolite samples are composed mainly of quartz, kaolinite, smectite-illite associations, and feldspars, traces of goethite, calcite, and evaporate minerals (sylvite, halite). The presence of calcite, dolomite, sylvite, and halite suggests the marine origin of the rocks, while trona mineral is a non-marine evaporate. The coexistence of these minerals in some of the analyzed samples suggests the deposition of sediments in a transitional environment of deposition. Traces of marine minerals are present in some of the samples but completely absent in others collected from another site. This suggests that the source rock formations from which the material originated are within the Upper Bima Sandstone interpreted as being deposited in a non-marine environment or the Yolde Formation, which is known as a transitional unit (transitional between the outcropping continental Upper Bima Sandstone and marine Pindiga Formation).
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Morales, Ethel, Hung Kiang Chang, Matías Soto, Gerardo Veroslavsky, Bruno Conti, Héctor de Santa Ana e Fernando Santos Corrêa. "Speculative petroleum systems of the Punta del Este Basin (offshore Uruguay)". Brazilian Journal of Geology 47, n. 4 (dicembre 2017): 645–56. http://dx.doi.org/10.1590/2317-4889201720170078.
Testo completoAbstract (sommario):
ABSTRACT: The Uruguayan continental margin was generated as the result of the breakup of Gondwana and, later, the opening of the South Atlantic Ocean, which began in the Jurassic. Three major areas of Meso-Cenozoic sedimentation are located in the Uruguayan offshore: the Punta del Este Basin, the southernmost sector of the Pelotas Basin and the Oriental del Plata Basin. These basins share the classical stages of tectono-sedimentary evolution of the other Atlantic basins, including the prerift (Paleozoic), rift (Jurassic-Early Cretaceous), transition (Barremian-Aptian) and postrift (Aptian-present) phases. Based on the analysis of basin evolution through seismic sections and well data as well as on the establishment of analogies with productive Atlantic basins, four speculative petroleum systems are proposed for the Punta del Este Basin: 1) Marine petroleum system of the prerift stage: Devonian/Permian-Devonian/Permian(?), 2) Lacustrine petroleum system of the synrift stage: Neocomian-Neocomian(?), 3) Marine petroleum system of the Cretaceous postrift: Aptian-Late Cretaceous(?), 4) Marine petroleum system of the Cenozoic postrift: Paleocene-Paleogene/Neogene(?).
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Tosi, Luigi, Cristina Da Lio, Pietro Teatini, Antonio Menghini e Andrea Viezzoli. "Continental and marine surficial water – groundwater interactions: the case of the southern coastland of Venice (Italy)". Proceedings of the International Association of Hydrological Sciences 379 (5 giugno 2018): 387–92. http://dx.doi.org/10.5194/piahs-379-387-2018.
Testo completoAbstract (sommario):
Abstract. Understanding the continental-marine surficial water–groundwater exchanges in transitional coastal environments is really challenging at large scale. It requires an image of the saltwater–freshwater relationship which is difficult to be obtained especially in wetlands, lagoons, and marine areas. This study is focused on the coastland of the southern Venice lagoon – northern Po river delta (Italy), a precarious environment subject to both natural changes and anthropogenic pressures. Here, saltwater severely affects farmlands and aquifers. We used an airborne electromagnetics (AEM) survey with the goal of characterizing the continental and marine surficial water–groundwater interactions in such coastal region. The AEM survey allowed depicting a clear image of the fresh water–saltwater occurrence in shallow aquifers along mainland-lagoon – littoral-sea profiles, up to 20 km long. The results reveal that continental groundwater is located in the lagoon subsoil below a 10–20 m thick saline aquifer and extends down to 70 m depth. The whole low-lying farmland located south of the lagoon margin is seriously affected by saltwater contamination, which occurs from a few to about 50 m depth. The integrated analysis of AEM, seismic and borehole data shows that buried morpho-geological structures, such as paleo-channels and over-consolidated clay units control the saline contamination from the lagoon and the sea into the coastal aquifer system.
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Bender, Adrian M., Richard O. Lease, Lee B. Corbett, Paul R. Bierman, Marc W. Caffee, James V. Jones e Doug Kreiner. "Yukon River incision drove organic carbon burial in the Bering Sea during global climate changes at 2.6 and 1 Ma". Earth Surface Dynamics 10, n. 5 (28 ottobre 2022): 1041–53. http://dx.doi.org/10.5194/esurf-10-1041-2022.
Testo completoAbstract (sommario):
Abstract. River erosion affects the carbon cycle and thus climate by exporting terrigenous carbon to seafloor sediment and by nourishing CO2-consuming marine life. The Yukon River–Bering Sea system preserves rare source-to-sink records of these processes across profound changes in global climate during the past 5 million years (Ma). Here, we expand the terrestrial erosion record by dating terraces along the Charley River, Alaska, and explore linkages among previously published Yukon River tributary incision chronologies and Bering Sea sedimentation. Cosmogenic 26Al/10Be isochron burial ages of Charley River terraces match previously documented central Yukon River tributary incision from 2.6 to 1.6 Ma during Pliocene–Pleistocene glacial expansion, and at 1.1 Ma during the 1.2–0.7 Ma Middle Pleistocene climate transition. Bering Sea sediments preserve 2–4-fold rate increases of Yukon River-derived continental detritus, terrestrial and marine organic carbon, and silicate microfossil deposition at 2.6–2.1 and 1.1–0.8 Ma. These tightly coupled records demonstrate elevated terrigenous nutrient and carbon export and concomitant Bering Sea productivity in response to climate-forced Yukon River incision. Carbon burial related to accelerated terrestrial erosion may contribute to CO2 drawdown across the Pliocene–Pleistocene and Middle Pleistocene climate transitions observed in many proxy records worldwide.
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Ma, Yuanzhen, Meng Wang, Ruying Ma, Jiamin Li, Asiya Bake e Yadi Shan. "Micropore Characteristics and Gas-Bearing Characteristics of Marine-Continental Transitional Shale Reservoirs in the East Margin of Ordos Basin". Adsorption Science & Technology 2021 (22 maggio 2021): 1–15. http://dx.doi.org/10.1155/2021/5593245.
Testo completoAbstract (sommario):
In order to deeply study the exploration potential of Carboniferous-Permian marine-continental transitional shale reservoirs in the Ordos Basin, the shale samples from well Y1 in the central-southern part of the Hedong Coalfield were used as the research object. The organic geochemical test, scanning electron microscope, X-ray diffraction, and high pressure mercury injection and low-temperature nitrogen adsorption experiments have studied the microscopic characteristics and gas content characteristics of shale reservoirs. The results show that the organic matter type of the sample is type III; the TOC content ranges from 0.28% to 16.87%, with an average of 2.15%; R o is from 2.45% to 3.36%, with an average value of 2.86%; the shale pores in the study area are well developed, containing more organic pores and intergranular pores of clay minerals. Based on the two-dimensional SEM image fractal theory to study different types of pores, the fractal dimension of shale pore fracture morphology is between 2.34 and 2.50, and the heterogeneity is moderate. The high-pressure mercury intrusion experiment characterizes the pore size distribution of shale macropores and transition pores. The pore diameters are mostly nm-scale. Transition pores are the main pores of the shale in the study area. Based on the characteristics of the pore structure, the adsorption capacity and gas content of CH4 in shale reservoir were analyzed by methane isothermal adsorption and gas content experiments. The results showed that the pore volume and specific surface area were positively correlated with clay mineral content, TOC, and RO, but negatively correlated with the quartz content. In clay minerals and brittle minerals, pore volume and specific surface area are positively correlated with illite content and negatively correlated with the quartz and kaolinite content. The measured total gas content and desorbed gas content are significantly positively correlated with TOC, but are weakly positively correlated with the quartz and illite content. This study finely characterizes the physical properties, micropore characteristics, gas-bearing characteristics, and influencing factors of shale reservoirs, which has certain theoretical guiding significance for the research and development of coal-measure shale in the Ordos Basin.
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GLÜCK, FRANZISKA U., SABINE STÖHR, RALF BOCHERT e MICHAEL L. ZETTLER. "Brittle stars (Echinodermata: Ophiuroidea) from the continental shelf off Angola and Namibia". Zootaxa 3475, n. 1 (10 settembre 2012): 1. http://dx.doi.org/10.11646/zootaxa.3475.1.1.
Testo completoAbstract (sommario):
The fauna occurring in waters off South-West Africa is of a remarkable composition and highly diverse due to local waterbodies, flow conditions and abiotic factors. These parameters predominate as a result of the cooperation of a major coastalupwelling system (the Benguela Current Large Marine Ecosystem), the Benguela Current flowing northwards, thesouthward directed Angola Current and the Angola–Benguela Frontal Zone formed in the transition zone of both watercurrents. This area has been insufficiently explored within the last decades and major gaps in biodiversity knowledge existto date. Two expeditions were conducted in 2004/2008, which collected benthic fauna samples. This is a list of brittle starsfound and a comprehensive research study relating to Ophiuroidea in waters off Angola and Namibia. 17 species could beidentified at depths from the littoral zone down to 125 m. The known depth and geographical distributions were extended for several species. Short diagnoses and ecological data are included.