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1
Boreham, S. „The Geology of the Wicken Vision Area, lower Cam valley, Cambridgeshire, UK“. Netherlands Journal of Geosciences - Geologie en Mijnbouw 92, Nr. 1 (April 2013): 47–59. http://dx.doi.org/10.1017/s0016774600000275.
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AbstractThe geology of the Wicken Vision Area in the lower Cam valley is described with reference to a stacked series of ten cross-sections through Holocene and Pleistocene deposits, and Cretaceous/Jurassic bedrock across the region. A detailed cross-section through a Holocene palaeochannel, with radiocarbon dating and pollen analyses is also presented. The structural geology of the bedrock and the stratigraphic arrangement of the Pleistocene and Holocene deposits are used to describe landscape development for the area. This study offers a new understanding of the stratigraphy and context of the Holocene, Weichselian and earlier Pleistocene deposits of the lower Cam valley, and provides a unique view of sediment architecture in valley-fill sediments at the fen edge.
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Boreham, Steve, und Karolina Leszczynska. „The Geology of the Middle Cam Valley, Cambridgeshire, UK“. Quaternary 2, Nr. 3 (12.07.2019): 24. http://dx.doi.org/10.3390/quat2030024.
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This study offers a new understanding of the stratigraphy and context of the Pleistocene (including Elsterian and Weichselian) and Holocene deposits of the Middle Cam valley, Cambridgeshire, United Kingdom, and provides a unique and detailed view of the sediment architecture of these valley-fill and interfluve sediments. The new insights into the geology of the area, including dating, pollen analyses, and sediment architecture, are presented with reference to a series of nine cross-sections through Holocene and Pleistocene deposits, as well as Cretaceous bedrock across the region. The structural geology of the bedrock and the stratigraphic arrangement of younger deposits are used to explain the landscape evolution of the area.
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Genov, Ivan. „Comment on “Holocene sedimentation in the southwestern Black Sea: Interplay between riverine supply, coastal eddies of the Rim Current, surface and internal waves, and saline underflow through the Strait of Bosphorus” by O. Ankindinova, A. E. Aksu, R. N. Hiscott [Marine Geology, 420 (2020) 106092]“. Review of the Bulgarian Geological Society 81, Nr. 2 (2020): 77–88. http://dx.doi.org/10.52215/rev.bgs.2020.81.2.6.
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Ankindinova et al. (2020) describe a series of hydrological events that have led to sedimentation and stratigraphic variations in the gradual sinking of the Black Sea shelf during the Holocene. A key aspect of the study is the attempt to provide a reliable stratigraphic basis for proving of a transgression in the basin throughout the Holocene. However, the conclusions of this approach run counter to the stratigraphic rules: redeposition and significant hiatus in the transgressive phase change of depth of sediment core location (M05-03P) – principle of superposition; merging of transgressive and regressive deposits into a common stratigraphic unit (contradicts the sequential stratigraphy). For this reason, the stability of the conclusion of Ankindinova et al. (2020) for the totally transgressive Holocene development of the Black Sea is doubtful. In addition, the study is based on the interpretation that the increase in the 87Sr /86Sr ratio is solely dependent on ocean water inflow, which is not always correct for enclosed and semi-enclosed basins.
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Zhou, Weijian, Zhisheng An und M. J. Head. „Stratigraphic Division of Holocene Loess in China“. Radiocarbon 36, Nr. 1 (1994): 37–45. http://dx.doi.org/10.1017/s0033822200014302.
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Loess deposition within the Loess Plateau of China records the history of environmental change over the last 2.5 Myr. Loess-paleosol sequences of the last 10 ka, which have preserved information of global climate change, relate closely to human occupation of the area. Hence, studies of the deposition and development of Holocene loess are significant for studying environmental change and problems associated with engineering geology. We present here stratigraphic relations among four profiles from the south, west and center of the Loess Plateau. On the basis of 14C radiometric and AMS dates of organic material extracted from the paleosols, together with magnetic susceptibility measurements down each profile, we discuss Holocene stratigraphic divisions within the Loess Plateau, and suggest that the Holocene optimum, characterized by paleosol complexes, occurred between 10 and 5 ka bp. From 5 ka BP to the present, neoglacial activity is characterized by recently deposited loess.
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Latypova, E. K., und B. L. Yakheemovich. „Geochronology of the Pleistocene and Holocene in the Fore-Urals“. Radiocarbon 35, Nr. 3 (1993): 441–47. http://dx.doi.org/10.1017/s003382220006046x.
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The paper presents the results for the 14C dating obtained recently in the Laboratory of the Institute of Geology, Ufa Science Centre, Russian Academy of Science, on the basis of megafaunal bones, peats, wood and mollusk shells. Dates are reported in stratigraphic sequence from the Late Würmian to the Holocene.
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Kurfurst, P. J., und S. R. Dallimore. „Engineering geology of nearshore areas off Richards Island, N.W.T.: a comparison of stable and actively eroding coastlines“. Canadian Geotechnical Journal 28, Nr. 2 (01.04.1991): 179–88. http://dx.doi.org/10.1139/t91-025.
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Nearshore areas off northern Richards Island can be expected to show considerable variability in lithology, strengths, and geothermal setting both in a temporal and a spatial sense. Drilling and laboratory studies carried out along onshore–offshore transects at a stable coastal site and an actively eroding coastal site have identified six major stratigraphic units of Holocene and pre-Holocene (Wisconsinan) age. The main factors controlling the geotechnical properties of these sediments and their distribution are the occurrence of shallow permafrost beneath areas seasonally covered by landfast sea ice, rapid degradation of permafrost in areas farther offshore, ice content of thawing pre-Holocene sediments, and variability in coastal processes. Key words: nearshore deposits, engineering geology, permafrost, physical properties, acoustic properties.
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Wheeler, A. J., und M. P. Waller. „The Holocene lithostratigraphy of Fenland, eastern England: a review and suggestions for redefinition“. Geological Magazine 132, Nr. 2 (März 1995): 223–33. http://dx.doi.org/10.1017/s0016756800011766.
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AbstractThe Fenland basin is filled with unconsolidated Holocene marine and freshwater deposits. Stratigraphic studies of the basin date back to 1877. This paper reviews the various lithostratigraphic schemes which have been proposed. Particular attention is paid to the presently accepted lithostratigraphy. Examples and a case study of a newly surveyed area are used to highlight its failings. Many of the difficulties experienced in Fenland are common to problems of lithostratigraphic classification in coastal lowland environments, as is demonstrated by reference to recent debate in the southeastern North Sea. In Fenland, as a result of the shortcomings of the various schemes, it is proposed that a new lithostratigraphy with formal stratotypes is devised. Suggestions are made as to the form this new stratigraphy could take. In the meantime, an informal lithostratigraphy should be adopted which has no regional or chronostratigraphic connotations.
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Allen, Wai K., Kenneth D. Ridgway, J. A. Benowitz, T. S. Waldien, S. M. Roeske, P. G. Fitzgerald und R. J. Gillis. „Neogene sedimentary record of the evolution of a translated strike-slip basin along the Denali fault system: Implications for timing of displacement, composite basin development, and regional tectonics of southern Alaska“. Geosphere 18, Nr. 2 (08.02.2022): 585–615. http://dx.doi.org/10.1130/ges02435.1.
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Abstract Analysis of the late Miocene to Holocene McCallum sedimentary basin, located along the south side of the eastern Denali fault system, provides a better understanding of strike-slip basin evolution, timing of displacement on the Denali fault, and tectonics of the southern Alaska convergent margin. Analysis of the McCallum basin utilizing measured stratigraphic sections, lithofacies analyses, and 40Ar/39Ar tephra ages documented a 564-m-thick, two-member stratigraphy. Fine-grained, lacustrine-dominated environments characterized deposition of the lower member, and coarse-grained, stream-dominated alluvial-fan environments characterized deposition of the upper member. The 40Ar/39Ar dating of tephras indicated that the lower member was deposited from 6.1 to 5.0 Ma, and the upper member was deposited from 5.0 to 3.8 Ma. Our stratigraphic analysis of the McCallum basin illuminates the development of a composite strike-slip basin, with the deposition of the lower member occurring along a transtensional fault section, and deposition of the upper member occurring along a transpressional fault section. This change in depositional and tectonic settings is interpreted to reflect ~79–90 km of transport of the basin along the Denali fault system based on Pleistocene–Holocene slip rates. Previous studies of the timing of Cenozoic displacement on the Denali fault system utilizing sedimentary records emphasized a Paleogene component; our findings, however, also require a significant Neogene component. Neogene strike-slip displacement and basin development along the Denali fault system were broadly coeval with development of high topography and related clastic wedges across southern Alaska in response to flat slab subduction of the Yakutat microplate.
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Thanh, Nguyen Trung, Paul Jing Liu, Mai Duc Dong, Dang Hoai Nhon, Do Huy Cuong, Bui Viet Dung, Phung Van Phach, Tran Duc Thanh, Duong Quoc Hung und Ngo Thanh Nga. „Late Pleistocene-Holocene sequence stratigraphy of the subaqueous Red River delta and the adjacent shelf“. VIETNAM JOURNAL OF EARTH SCIENCES 40, Nr. 3 (04.06.2018): 271–87. http://dx.doi.org/10.15625/0866-7187/40/3/12618.
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The model of Late Pleistocene-Holocene sequence stratigraphy of the subaqueous Red River delta and the adjacent shelf is proposed by interpretation of high-resolution seismic documents and comparison with previous research results on Holocene sedimentary evolution on the delta plain. Four units (U1, U2, U3, and U4) and four sequence stratigraphic surfaces (SB1, TS, TRS and MFS) were determined. The formation of these units and surfaces is related to the global sea-level change in Late Pleistocene-Holocene. SB1, defined as the sequence boundary, was generated by subaerial processes during the Late Pleistocene regression and could be remolded partially or significantly by transgressive ravinement processes subsequently. The basal unit U1 (fluvial formations) within incised valleys is arranged into the lowstand systems tract (LST) formed in the early slow sea-level rise ~19-14.5 cal.kyr BP, the U2 unit is arranged into the early transgressive systems tract (E-TST) deposited mainly within incised-valleys under the tide-influenced river to estuarine conditions in the rapid sea-level rise ~14.5-9 cal.kyr BP, the U3 unit is arranged into the late transgressive systems tract (L-TST) deposited widely on the continental shelf in the fully marine condition during the late sea-level rise ~9-7 cal.kyr BP, and the U4 unit represents for the highstand systems tract (HST) with clinoform structure surrounding the modern delta coast, extending to the water depth of 25-30 m, developed by sediments from the Red River system in ~3-0 cal.kyr BP.ReferencesBadley M.E., 1985. Practical Seismic Interpretation. International Human Resources Development Corporation, Boston, 266p.Bergh G.D. 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Earth-Science Reviews, 92, 1-33.Catuneanu O., Galloway W.E., Kendall C.G. St C., Miall A.D., Posamentier H.W., Strasser A. and Tucker M.. E., 2011. Sequence Stratigraphy: Methodology and Nomenclature. Newsletters on Stratigraphy, 44(3), 173-245.Coleman J.M and Wright L.D., 1975. Modern river deltas: variability of processes and sand bodies. In: Broussard M.L (Ed), Deltas: Models for exploration. Houston Geological Society, Houston, 99-149.Doan Dinh Lam, 2003. History of Holocene sedimentary evolution of the Red River delta. PhD thesis in Vietnam, 129p (in Vietnamese).Duc D.M., Nhuan M.T, Ngoi C.V., Nghi T., Tien D.M., Weering J.C.E., Bergh G.D., 2007. Sediment distribution and transport at the nearshore zone of the Red River delta, Northern Vietnam. Journal of Asian Earth Sciences, 29, 558-565.Dung B.V., Stattegger K., Unverricht D., Phach P.V., Nguyen T.T., 2013. Late Pleistocene-Holocene seismic stratigraphy of the Southeast Vietnam Shelf. 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Journal of Asian Earth Sciences, 23, 113-126.Hanebuth T.J.J., Voris H.K.., Yokoyama Y., Saito Y., Okuno J., 2011. Formation and fate of sedimentary depocenteres on Southeast Asia’s Sunda Shelf over the past sea-level cycle and biogeographic implications. Eath-Science Reviews, 104, 92-110.Hanebuth T., Stattegger K and Grootes P. M., 2000. Rapid flooding of the Sunda Shelf: a late-glacial sea-level record. Science, 288, 1033-1035.Helland-Hansen W and Gjelberg, J.G., 1994. Conceptual basis and variability in sequence stratigraphy: a different perspective. Sedimentary Geology, 92, 31-52.Hori K., Tanabe S., Saito Y., Haruyama S., Nguyen V., Kitamura., 2004. Delta initiation and Holocene sea-level change: example from the Song Hong (Red River) delta, Vietnam. Sedimentary Geology, 164, 237-249.Hunt D. and Tucker M.E., 1992. Stranded parasequences and the forced regressive wedge systems tract: deposition during base-level fall. Sedimentology Geology, 81, 1-9.Hunt D. and Tucker M.E., 1995. Stranded parasequences and the forced regressive wedge systems tract: deposition during base-level fall-reply. Sedimentary Geology, 95, 147-160.Lam D.D. and Boyd W.E., 2000. Holocene coastal stratigraphy and model for the sedimentary development of the Hai Phong area in the Red River delta, north Vietnam. Journal of Geology (Series B), 15-16, 18-28.Lieu N.T.H., 2006. Holocene evolution of the Central Red River Delta, Northern Vietnam. PhD thesis of lithological and mineralogical in Germany, 130p.Luu T.N.M., Garnier J., Billen G., Orange D., Némery J., Le T.P.Q., Tran H.T., Le L.A., 2010. Hydrological regime and water budget of the Red River Delta (Northern Vietnam). Journal of Asian Earth Sciences, 37, 219-228.Mather S.J., Davies J., Mc Donal A., Zalasiewicz J.A., and Marsh S., 1996. The Red River Delta of Vietnam. British Geological Survey Technical Report WC/96/02, 41p.Mathers S.J. and Zalasiewicz J.A.,1999. Holocene sedimentary architecture of the Red River delta, Vietnam. Journal of Coastal Research, 15, 314-325.Milliman J.D. and Mead R.H., 1983. Worldwide delivery of river sediment to the oceans. Journal of Geology, 91, 1-21.Milliman J.D and Syvitski J.P.M., 1992. Geomorphic/tectonic control of sediment discharge to the Ocean: the importance of small mountainous rivers. Journal of Geology, 100, 525-544.Mitchum Jr. R.M., Vail P.R., 1977. Seismic stratigraphy and global changes of sea-level. Part 7: stratigraphic interpretation of seismic reflection patterns in depositional sequences. In: Payton C.E. (Ed.), Seismic Stratigraphy-Applications to Hydrocarbon Exploration, A.A.P.G. Memoir, 26, 135-144.Nguyen T.T., 2017. Late Pleistocene-Holocene sedimentary evolution of the South East Vietnam Shelf, PhD thesis (in Vietnamese), Hanoi University of Science, Vietnam, 169p.Nummedal D., Riley G.W., Templet P.T., 1993. High-resolution sequence architecture: a chronostratigraphic model based on equilibrium profile studies. In: Posamentier H.W., Summerhayes C.P., Haq B.U., Allen G.P. (Eds.), Sequence stratigraphy and Facies Associations. International Association of Sedimentologists Special Publication, 18, 55-58.Posamentier H.W. and Allen G.P., 1999. Siliciclastic sequence stratigraphy: concepts and applications. SEPM Concepts in Sedimentology and Paleontology, 7, 210p.Posamentier H.W., Jervey M.T. and Vail P.R., 1988. Eustatic controls on clastic deposition I-Conceptual framework. Sea-level changes-An Integrated Approach, The Society of Economic Paleontologists and Mineralogist. SEPM Special Publication, 42, 109-124.Reineck H.E., Singh I.B., 1980. Depositional sedimentary environments with reference to terrigenous clastics. Springer-Verlag Berlin Heidelberg New York, 551p. Ross K., 2011. Fate of Red River Sediment in the Gulf of Tonkin, Vietnam. Master Thesis. North Carolina State University, 91p.Saito Y., Katayama H., Ikehara K., Kato Y., Matsumoto E., Oguri K., Oda M., Yumoto M. 1998. Transgressive and highstand systems tracts and post-glacial transgression, the East China Sea. Sedimentary Geology, 122, 217-232.Stattegger K., Tjallingii R., Saito Y., Michelli M., Nguyen T.T., Wetzel A., 2013. Mid to late Holocene sea-level reconstruction of Southeast Vietnam using beachrock and beach-ridge deposits. Global and Planetary Change, 110, 214-222.Tanabe S., Hori K., Saito Y., Haruyama S., Doanh L.Q., Sato Y., Hiraide S., 2003a. Sedimentary facies and radiocarbon dates of the Nam Dinh-1 core from the Song Hong (Red River) delta, Vietnam. Journal of Asian Earth Sciences, 21, 503-513.Tanabe S., Hori K., Saito Y., Haruyama S., Phai V.V., Kitamura A., 2003b. Song Hong (Red River) delta evolution related to millennium-scale Holocene sea-level changes. Quaternary Science Reviews, 22(21-22), 2345-2361.Tanabe S., Saito Y., Lan V.Q., Hanebuth T.J.J., Lan N.Q., Kitamura A., 2006. Holocene evolution of the Song Hong (Red River) delta system, northern Vietnam. Sedimentary Geology, 187, 29-61.Thanh T.D. and Huy D.V., 2000. Coastal development of the modern Red River Delta. Bulletin of the Geological Survey of Japan, 5, 276.Tjallingii R., Stattegger K., Wetzel A., Phung VP., 2010. Infilling and flooding of the Mekong River incised valley during deglacial sea-level rise. Quaternary Science Reviews, 29, 1432-1444.Vail P.R., 1987. Seismic stratigraphy interpretation procedure. In: Bally, A.W. (Ed), Atlats of Seismic Stratigraphy. American Association of Petroleum Geologist Studies in Geology, 27, 1-10.Van Wagoner J.C., Posamentier H.W., Mitchum R.M., Vail P.R., Sarg P.R., Louit J.F., Hardenbol J., 1988. An overview of the fundamental of sequence stratigraphy and key definitions. An Integrated Approach, SEPM Special Publication, 42, 39-45.Veeken P.C.H., 2006. Seismic stratigraphy Basin Analysis and Reservoir Characterization. Handbook of geophysical exploration, Elsevier, Oxford, 37509p.Yoo D.G., Kim S.P., Chang T.S., Kong G.S., Kang N.K., Kwon Y.K., Nam S.L., Park S.C., 2014. Late Quaternary inner shelf deposits in response to late Pleistocene-Holocene sea-level changes: Nakdong River, SE Korea. Quaternary International, 344, 156-169.
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Tessier, Bernadette, Isabelle Billeaud und Patrick Lesueur. „Stratigraphic organisation of a composite macrotidal wedge: the Holocene sedimentary infilling of the Mont-Saint-Michel Bay (NW France)“. Bulletin de la Société Géologique de France 181, Nr. 2 (01.03.2010): 99–113. http://dx.doi.org/10.2113/gssgfbull.181.2.99.
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Abstract The Mont-Saint-Michel Bay (NW France) is a composite macrotidal environment that was filled up in the course of the Holocene transgression and sea-level highstand. Three main sub-environments constitute the present-day landscape of the bay: 1) a wide embayment with extensive mud to sandflats in the south, 2) a sandy to muddy channel-and-shoal estuarine system in the east, 3) a wave-dominated sandy coast composed of beach and dune barrier in the north. The Holocene infill of this composite macrotidal basin has been studied thanks to a set of vibrocores and VHR seismic data. The main results are summarized as follows: the TST is composed by a low-energy aggradational unit in the axis of the estuarine valley, and by high-energy sediment bodies (tidal dunes and banks) outside the valley; the HST (post 6500 yr B.P.) constitutes the main component of the infill. In the north, it is characterised by an aggradational unit made of back-barrier tidal lagoonal infill successions. In the embayment, it is represented by an aggradational unit composed of tidal-flat deposits. In the estuarine axis, the HST is constituted by a sand-dominated tidal channel-and-shoal belt. The rate of the Holocene sea-level rise appears to be the main factor of control of the infill architecture of the Mont-Saint-Michel Bay since the most significant change occurred around 6500 yr B.P. when the transgression slowed down. The interaction between hydrodynamic agents and sediment supply exerts as well a key control, especially during the late Holocene, when transgression is slow. The impact of climate changes is recorded in the infill during this period. The rocky substrate hypsometry should be considered also as a major forcing parameter as it determines the potential of preservation of the infill in relation with the depth of ravinement by tidal currents.
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Ortega-Guerrero, Beatriz, Sandra García, Guadalupe Cruz, Claudio Salinas, Margarita Caballero, Ismerai Reyes und Lizeth Caballero. „Holocene and Upper Pleistocene stratigraphy of Xochimilco lake, central Mexico“. Revista Mexicana de Ciencias Geológicas 39, Nr. 2 (26.07.2022): 167–78. http://dx.doi.org/10.22201/cgeo.20072902e.2022.2.1687.
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The lacustrine system developed in the basin of Mexico has been of great interest in studies of various geological and social disciplines. Its sediments preserve the history of the environmental changes that occurred during the late Quaternary. Between 2016 and 2018, a set of lacustrine sediment cores were collected in the Xochimilco sub-basin, located south of the basin of Mexico. From these sedimentary sequences, a master sequence was constructed that represents the upper 66.5 m of the lacustrine deposits. For the establishment of its stratigraphic column, 15 lithotypes were defined from their sedimentary components in which the clastic components made up of silicates dominate, mostly silt and clay in size. The most abundant biogenic fraction is diatoms that frequently form oozes, and ostracods are a common component in most of the sequence, which locally form hashes. Interbedded with the clastic and biogenic lithotypes are volcaniclastic deposits. Eight lithological units were defined based on their dominant lithotypes. The time scale of the sequence is still uncertain for the oldest sediments; however, it is estimated that it covers the last 300000 to 350000 years. From this temporality, environmental oscillations of millennial scales are inferred. Diatom-rich laminated sediments represent the deepest phases in the lake. The deposits with higher biogenic and authigenic calcareous components indicate the phases of higher ionic concentration during which the lake was shallower. The detailed analysis of the stratigraphy and the description of the sedimentary components in Xochimilco allows to establish an initial interpretation of the variations in the depositional environments, and provides the base from which the detailed studies of paleoclimatic indicators will be supported.
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Mikharevich, M. V., und A. V. Shpansky. „PROBLEMS OF AGE AND GENETIC DIAGNOSTICS OF QUATERNARY DEPOSITS IN THE VALLEY OF THE YENISEI RIVER MIDDLE COURSE (YENISEI – LOWER ANGARA STRATIGRAPHIC REGION AND THE MINUSINSK BASINS AREA)“. Geology and mineral resources of Siberia, Nr. 10s (Dezember 2021): 57–68. http://dx.doi.org/10.20403/2078-0575-2021-10c-57-68.
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The article is devoted to the state of stratigraphic exploration maturity of the Eopleistocene – Neo-Рleistocene Quaternary deposits on the boundary of mountain and plain territories in the non-glacial area. The material analysis shows an inadequate rationale of the existing stratigraphic schemes, according to which the ladder of alluvial terraces of these territories was formed sequentially during the Eopleistocene, Neo-Pleistocene and Holocene. The revising of representative sections was carried out, the provision of them with geochronological data, the accuracy of age and genetic diagnostics were evaluated.
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Hansen, Louise, Raymond Eilertsen, Inger-Lise Solberg und Kåre Rokoengen. „Stratigraphic evaluation of a Holocene clay-slide in Northern Norway“. Landslides 4, Nr. 3 (20.01.2007): 233–44. http://dx.doi.org/10.1007/s10346-006-0078-4.
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Tessier, Bernadette, Nicolas Delsinne und Philippe Sorrel. „Holocene sedimentary infilling of a tide-dominated estuarine mouth. The example of the macrotidal Seine estuary (NW France)“. Bulletin de la Société Géologique de France 181, Nr. 2 (01.03.2010): 87–98. http://dx.doi.org/10.2113/gssgfbull.181.2.87.
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Abstract The results of a seismo-stratigraphic study performed to study the Holocene sedimentary infilling at the mouth of the Seine River are presented. Combined data comprise very high resolution seismic reflection profiles, vibrocores, up to 4.5 m long, radiocarbon dating and old bathymetric charts. The infill is divided into two main stages: the transgressive systems tract, relative to the early Holocene high rate of sea-level rise, from 9000 to 7000 cal B.P., made of fine-grained, organic-rich, tidal flat to swamp deposits; the highstand systems tract, relative to the middle to late Holocene low rate of sea-level rise, from 7000 to 3000 cal B.P., characterized by the development of the high energy estuarine body above the main axis of the incised valley. Simultaneously, on the southern edge of the valley, a coastal barrier constructed above a bedrock plateau under the dominant action of waves. At 3000 cal B.P., probably in relation to a major climatic deterioration, the destruction of the barrier occurred and the tidal estuarine body expanded finally over the whole incised valley area. The rate of sea-level rise and the bedrock morphology appear to be the two main key-factors that control the sedimentary infilling architecture of this macrotidal, tide-dominated estuarine setting at the pluri-millenium Holocene time scale. Also, rapid climate changes determine part of the infill pattern, especially during the late Holocene sea-level highstand context.
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Larsen, B., und L. T. Andersen. „Late Quaternary stratigraphy and morphogenesis in the Danish eastern North Sea and its relation to onshore geology“. Netherlands Journal of Geosciences 84, Nr. 2 (Juli 2005): 113–28. http://dx.doi.org/10.1017/s0016774600023003.
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AbstractGeological structures and Late Quaternary stratigraphy of the shallow subsurface along the southernmost Danish North Sea coast have been investigated using seismic data and shallow boreholes. A large-scale glaciotectonic thrust complex has been mapped in an area of 15 km by 40 km in the Fanø Bugt area. The affected succession consists of Neogene and Quaternary sediments deformed down to a depth of 200 – 360 m. A kineto-stratigraphic correlation to onshore glaciotectonic deformation suggests that the deformation took place during a westward advance stage of the Late Saalian (Warthe) glaciation. The western limit of the glaciotectonic structures constitutes an N-S striking deformation front situated 35 km off the west coast. Based on the glacial stratigraphy outside the deformation front, it is suggested that the same ice advance that caused the glaciotectonic deformation, eroded the top of the thrust sheets, and subsequently deposited a lower unit of meltwater sediments and an upper heterogenous glacigenic unit. The upper glacigenic unit forms a bank about 30 km offshore. Between the bank and the shore, the surface of the Saalian glacial landscape forms a wide depression ca. 50 m below sea level. This basin has controlled deposition in the area since the late Saalian and is filled with sediments of late Saalian, Eemian, Weichselian and Holocene age. The base of the Holocene marine deposits is thus a flat erosional surface extending eastward several kilometres below the onshore coastal areas and the northern Wadden Sea. This surface was transgressed 8800 years ago. An inverted, in plan view T-shaped, Holocene sand accumulation approximately 25 km long, 30 km wide and 15 – 25 m thick is situated on top of this surface at Blåvands Huk. According to recent estimates by the Danish Coastal Protection Board some 2.5 million m3 sediments are supplied annually to the system from the north. In the last 3000 years, 25 km of the west coast and the associated shoreface slope have prograded ca. 3 km towards the west forming a barrier spit complex. Large aeolian dunes and cover sands now conceal the spit complex. Extending twenty km west of Blåvands Huk is a highly dynamic bank, the Inner Horns Rev, with active sand-accumulation on the slopes. The Inner Horns Rev bank has grown ca. 3.5 km westward during the last 800 years. The deposits seem to be sourced by the coastal longshore sand transport from the north. The Outer Horns Rev was previously assumed to be a Saalian terminal moraine. However, this investigation reveals that it is also mainly a Holocene marine accumulation landform, but sourced from the west. Other sand accumulations, which are situated 20 – 30 km west of the coast, are probably sourced from both the south and the west.
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Isla, Manuel F., Ernesto Schwarz, Gonzalo D. Veiga, Jerónimo J. Zuazo und Mariano N. Remirez. „Discriminating intra-parasequence stratigraphic units from two-dimensional quantitative parameters“. Journal of Sedimentary Research 91, Nr. 8 (27.08.2021): 887–911. http://dx.doi.org/10.2110/jsr.2020.203.
Annotation:
ABSTRACT The intra-parasequence scale is still relatively unexplored territory in high-resolution sequence stratigraphy. The analysis of internal genetic units of parasequences has commonly been simplified to the definition of bedsets. Such simplification is insufficient to cover the complexity involved in the building of individual parasequences. Different types of intra-parasequence units have been previously identified and characterized in successive wave-dominated shoreface–shelf parasequences in the Lower Cretaceous Pilmatué Member of the Agrio Formation in central Neuquén Basin. Sedimentary and stratigraphic attributes such as the number of intra-parasequence units, their thickness, the proportions of facies associations in the regressive interval, the lateral extent of bounding surfaces, the degree of deepening recorded across these boundaries, and the type and lateral extent of associated transgressive deposits are quantitatively analyzed in this paper. Based on the analysis of these quantified attributes, three different scales of genetic units in parasequences are identified. 1) Bedset complexes are 10–40 m thick, basin to upper-shoreface successions, bounded by 5 to 16 km-long surfaces with a degree of deepening of one to three facies belts. These stratigraphic units represent the highest hierarchy of intra-parasequence stratigraphic units, and the vertical stacking of two or three of them typically forms an individual parasequence. 2) Bedsets are 2–20 m thick, offshore to upper-shoreface successions, bounded by up to 10 km long surfaces with a degree of deepening of zero to one facies belt. Two or three bedsets stack vertically build a bedset complex. 3) Sub-bedsets are 0.5–5 m thick, offshore transition to upper-shoreface successions, bounded by 0.5 to 2 km long surfaces with a degree of deepening of zero to one facies belt. Two or three sub-bedsets commonly stack to form bedsets. The proposed methodology indicates that the combination of thickness with the proportion of facies associations in the regressive interval of stratigraphic units can be used to discriminate between bedsets and sub-bedsets, whereas for higher ranks (bedsets and bedset complexes) the degree of deepening, lateral extent of bounding surfaces, and the characteristics of associated shell-bed deposits become more effective. Finally, the results for the Pilmatué Member are compared with other ancient and Holocene examples to improve understanding of the high-frequency evolution of wave-dominated shoreface–shelf systems.
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Frey, R. W., und J. D. Howard. „Beaches and beach-related facies, Holocene barrier islands of Georgia“. Geological Magazine 125, Nr. 6 (November 1988): 621–40. http://dx.doi.org/10.1017/s0016756800023438.
Annotation:
AbstractThe mesotidal coast of Georgia encompasses diverse sedimentary features and depositional environments, most of which typify major facies of the entire Georgia Bight – a broad embayment on the southeastern U.S. shelf. Barrier island strandline environments especially include tidal inlets and shoals, the beach shoreface, foreshore, and backshore, and dunes and washover fans. Low energy beach segments may grade directly into small seaside tidal flats. Relict salt marsh deposits crop out on erosional beaches. All deposits are in dynamic equilibrium with fluctuating coastal conditions and a gradual rise in sea level.Most of these facies are important in interpreting ancient epeiric transgressive/regressive coastal sequences. Pronounced local variations in the overall sequence result from complex latero-vertical relationships between (1) the shoreface, foreshore, and shoals, and (2) the shoals, low energy beaches, and beach-related tidal flats. Washover fans and relict deposits on erosional beaches cause perturbations within present day lateral relationships but are normal in transgressive facies tracts along such coasts. Close stratigraphic control of outcrops or cores would be necessary for detailed reconstructions of, or correlations among, ancient analogs.
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Gaudenyi, Tivadar, Drazenko Nenadic, Mladjen Jovanovic und Petar Stejic. „The revision of quaternary stratigraphy of the Zrenjanin artesian well borehole profile (Banat, Vojvodina, Serbia)“. Annales g?ologiques de la Peninsule balkanique, Nr. 00 (2022): 7. http://dx.doi.org/10.2298/gabp210306007g.
Annotation:
The geological analysis of artesian borehole material from Sombor, Subotica, and Zrenjanin, was in the first campaign of detailed stratigraphic studies of Vojvodina in 1892-1895. The results of Quaternary stratigraphy from Zrenjanin were published by HalavAts m ore than a decade later (1914). The significance of the Zrenjanin, Sombor, and Subotica artesian well profiles for more than a century is considered the representative local profiles for the Quaternary stratigraphy of Vojvodina recognized by Serbian (Yugoslavian) and Hungarian geologists. Significant changes were after the taxonomical revision of molluscan material and its stratigraphic context, which was done through the excellent work of Krolopp in the 1970-ies. Unfortunately, the mentioned changes were not applied in the studies during the geological surveying of former Yugoslavia. The developments in Quaternary geology, changes in the Quater nary chronostratigraphic scale, and the results shown by this paper enable the Lower Pleistocene fluvial deposits to be defined as the Pleistocene Corbicula beds, the Viviparus boeckhi Horizon. The Lower Pleistocene at Zrenjanin was documented from 234.54 to 58.36 m depth. The interval between 234.54 and 208.50 m comprises the Upper Paludina - Viviparus vucotinovici zone, while the Viviparus boeckhi Horizons were identified between 135.18 m and 58.36 m. The interval between 58.36 m and 37.75 m is defined as Pleistocene (Lower- and Middle Pleistocene) based on sedimentological and the molluscan record. The interval from 37.75 m to 21.67 m depth was identified as Middle Pleistocene, according to its lithology and the paleontological material. The fluvial sediments? 21.69 m and 7.31 m depths cannot be determined according to the faunistic data; we can only consider them as Pleistocene age. The Holocene sediment and soil horizons ascend to a 2.90 m depth.
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Erskine, Wayne D., und M. D. Melville. „Geomorphic and stratigraphic complexity: holocene alluvial history of upper wollombi brook, australia“. Geografiska Annaler: Series A, Physical Geography 90, Nr. 1 (März 2008): 19–35. http://dx.doi.org/10.1111/j.1468-0459.2008.00331.x.
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Amos, Salvador. „A stable Cenozoic geologic time scale is indispensable“. GeoArabia 11, Nr. 4 (01.10.2006): 155–57. http://dx.doi.org/10.2113/geoarabia1104155.
Annotation:
A stable, standard geologic time scale is indispensable for the clear and precise communication among geologists; it is a basic tool of geologic work. Considerable progress has been made to achieve such a stable time scale. However, during the last few years several proposals have been made to modify the Cenozoic section of the geologic time scale that threaten to destabilize it. Seven articles published in Episodes since 2000 that could contribute to this destabilization are discussed. They provide excellent examples of the profusion of different terminologies, hierarchies, and stratigraphic relationships that have been proposed: to eliminate the Tertiary and the Quaternary or to raise their rank to suberathems; to extend the Neogene to the present, to make the Quaternary a formal subsystem of the Neogene, or consider it an informal stratigraphic unit; to eliminate the Holocene, and to decouple the base of the Pleistocene from the base of the Quaternary. If adopted, these proposals would cause nothing but great confusion and controversy. They disregard the clear preferences of geologists the world over as reflected by the terminology they have been using for many decades. Common sense would dictate the continued use of this terminology in its current, widely accepted form.
21
Lomando, Anthony J. „Structural Influences on Facies Trends of Carbonate Inner Ramp Systems, Examples from the Kuwait-Saudi Arabian Coast of the Arabian Gulf and Norhtern Yucatan, Mexico“. GeoArabia 4, Nr. 3 (01.07.1999): 339–60. http://dx.doi.org/10.2113/geoarabia0403339.
Annotation:
ABSTRACT The value of integrating structural influences with sedimentology is identifying the significant changes that occur along strike and downdip. Understanding where and how these changes occur can have a profound influence on exploration risk assessment along inner ramp and inner shelf trends, particularly in the search for stratigraphic traps. Dip-oriented structural elements along depositional strike of inner ramps of the discussed areas include major fault zones, folds, smaller faults, and impact craters. These tectonic influences control often discontinuous facies distribution patterns of barrier islands, lagoons, sabkhas, and inner ramp carbonate factories. In contrast, strike-oriented structural influences often control the location of facies trends which promotes trend continuity. Wave-dominated Holocene and modern inner ramp deposits from southern Kuwait-northern Saudi Arabia and Northern Yucatan, Mexico, provide complementary models to the classic channelized ramp system of Abu Dhabi. Structural influences relative to coastal orientations control regional and local depositional styles, trend continuity/discontinuity, the location of carbonate factories and landward lagoon and tidal flat depositional characteristics. As reservoir-updip seal pairs for stratigraphic trap exploration, these analogues also demonstrate that changes along depositional strike should be expected, and in many cases could be predictable. These relationships emphasize the need to carefully integrate structure with facies and paleo-environmental reconstructions when mapping trends and assessing exploration risk in the search for stratigraphic and combination traps.
22
Manyuk, Volodymyr. „Geological history of the Dnipro Rapids from Paleogene to Holocene“. Journal of Geology, Geography and Geoecology 28, Nr. 1 (20.04.2019): 114–32. http://dx.doi.org/10.15421/111913.
Annotation:
During its long history, the rapids section of the large river the Dnipro not only posed a problem for navigation, but also attracted people with its picturesque rocky landscapes unusual for the Steppe Prydniprovie. Nobody who had saw their beauty was left indifferent. History has preserved lots of recorded impressions from various visits to the Rapids from the Ancient Greek philosphers to exceptional works of Dmitro Yavornytsky. However, the geological studies were fragmented and there is no integrated source focussing on the geological structure of the Dnipro Rapids. We analyzed the results of the explorations of Valerian Domger, a famous researcher of the geology of Middle Prydniprovie.His routes investigated almost every corner of the then Katerynoslav governorate. After the creation of the Prydriprovie Regional Landscape Park (PRLP) in 2008 within the territory of part of the Dnipro Rapids, a question of restoration of its geological history should have emerged, but that has not happened. The year 2017 became the year of rebirth of the PRLP andrecognition of geological component as the key feature of its restoration. The Pre-Cambrian stage of the geological history of the Naddniprovia Rapids is described in the author`s publication in early 2018, which focused on the most ancient history of the Rapids. The Phanerozoic Eon is analyzed in this work and focuses on the lithogical-facial peculiarities of the sedimentary rocks from Paleogene to Quaternary rocks on the basis of stratigraphic and paleontological data, according to which they have beendivided in detail. We determined the patterns in the structure of Quaternary deposits, the correlation of subaerial and subaquaticformations of different genetic types was made according to the use of the climatic-stratigraphic or paleoclimatic principle of division. Thepossibilities of creating a geological park on the basis of the“Dnipro Rapids” Regional Landscape Park ( "Dniprovi Porohy' RLP) areexplored and substantiated.
23
Bitinas, A., A. Damušytė, G. Hütt, T. Martma, G. Ruplėnaitė, M. Stančikaitė, D. Ūsaitytė und R. Vaikmäe. „STRATIGRAPHIC CORRELATION OF LATE WEICHSELIAN AND HOLOCENE DEPOSITS IN THE LITHUANIAN COASTAL REGION“. Proceedings of the Estonian Academy of Sciences. Geology 49, Nr. 3 (2000): 200. http://dx.doi.org/10.3176/geol.2000.3.03.
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Zanchetta, Giovanni, Marta Pappalardo, Alessio Di Roberto, Monica Bini, Ilenia Arienzo, Ilaria Isola, Adriano Ribolini et al. „A Holocene tephra layer within coastal aeolian deposits north of Caleta Olivia (Santa Cruz Province, Argentina)“. Andean Geology 48, Nr. 2 (31.05.2021): 267. http://dx.doi.org/10.5027/andgeov48n2-3290.
Annotation:
In this paper we illustrate the stratigraphy, geochronology, and geochemistry (major, minor, trace elements and Sr-isotopes) of a Holocene tephra layer found within coastal sedimentary deposits north of Caleta Olivia (Santa Cruz Province, Argentina). The stratigraphic succession comprises beach deposits with basal erosive surface resting on the local substrate (“Formación Patagonia”) followed by a poorly developed paleosoil. The paleosoil is covered by a lenticular fine-grained (Mdφ: 5.2, 0.027 mm), well sorted (σφ: 1.2) volcanic ash layer and aeolian sands. The geochemical composition of shard fragments points to an origin from the Hudson volcano, located in the southern Andes, ca. 400 km to the west. The geochemistry, Sr-isotopes and the radiometric constraints (younger than the age of the underlying marine layer dated at ca. 4,100 a cal BP) further allow correlating this tephra with the so-called H2 eruption (ca. 3,900 a cal BP). This finding is of interest owing to the poor preservation potential of tephra within the Late Holocene sedimentary deposits of the Atlantic coast of Patagonia and represents the first finding of H2 eruption in this area, improving our knowledge of the dispersion of the fine-grained distal deposit of the Hudson volcanic explosive activity, thus allowing a better estimate of the eruptive dynamics and the risks associated with the Hudson volcano.
25
Zol'nikov, I. D., und S. A. Gus'kov. „The paleogeographic and stratigraphic confinement of giant floods in West Siberia in the Late Neopleistocene–Holocene“. Russian Geology and Geophysics 50, Nr. 2 (Februar 2009): 143–47. http://dx.doi.org/10.1016/j.rgg.2008.08.003.
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Corrado, Giuseppe, Sabrina Amodio, Pietro P. C. Aucelli, Gerardo Pappone und Marcello Schiattarella. „The Subsurface Geology and Landscape Evolution of the Volturno Coastal Plain, Italy: Interplay between Tectonics and Sea-Level Changes during the Quaternary“. Water 12, Nr. 12 (02.12.2020): 3386. http://dx.doi.org/10.3390/w12123386.
Annotation:
The Volturno alluvial-coastal plain is a relevant feature of the Tyrrhenian side of southern Italy. Its plan-view squared shape is due to Pliocene-Quaternary block-faulting of the western flank of the south-Apennines chain. On the basis of the stratigraphic analysis of almost 700 borehole logs and new geomorphological survey, an accurate paleoenvironmental reconstruction before and after the Campania Ignimbrite (CI; about 40 ky) eruption is here presented. Tectonics and eustatic forcing have been both taken into account to completely picture the evolution of the coastal plain during Late Quaternary times. The upper Pleistocene-Holocene infill of the Volturno plain has been here re-organized in a new stratigraphic framework, which includes seven depositional units. Structural analysis showed that two sets of faults displaced the CI, so accounting for recent tectonic activity. Yet Late Quaternary tectonics is rather mild, as evidenced by the decametric vertical separations operated by those faults. The average slip rate, which would represent the tectonic subsidence rate of the plain, is about 0.5 mm/year. A grid of cross sections shows the stratigraphic architecture which resulted from interactions among eustatic changes, tectonics and sedimentary input variations. On the basis of boreholes analysis, the trend of the CI roof was reconstructed. An asymmetrical shape of its ancient morphology—with a steeper slope toward the north-west border—and the lack of coincidence between the present course of the Volturno River and the main buried bedrock incision, are significant achievements of this study. Finally, the morpho-evolutionary path of the Volturno plain has been discussed.
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Lyon, Eva C., Michael M. McGlue, Edward W. Woolery, Sora L. Kim, Jeffery R. Stone und Susan R. H. Zimmerman. „Sublacustrine geomorphology and modern sedimentation in a glacial scour basin, June Lake, eastern Sierra Nevada, U.S.A.“ Journal of Sedimentary Research 89, Nr. 10 (21.10.2019): 919–34. http://dx.doi.org/10.2110/jsr.2019.52.
Annotation:
ABSTRACT Small sub-alpine glacial lakes are often targeted as Holocene paleoclimate archives, but their evolution as landforms and depositional basins is understudied. At June Lake in the eastern Sierra Nevada of California (USA), bathymetry, surface sediment composition, and seismic stratigraphy are studied to assess the modern sedimentary system and gain insight into the basin's origins. A basin-wide seismic survey reveals sublacustrine morphological features that attest to the role of ice in scouring the June Lake basin, including a prominent abraded bedrock shoal and an adjacent overdeepened depression. The seismic survey reveals four acoustically distinct stratigraphic units that reflect the history of sedimentation following glacial scouring. The youngest of these is represented in the recovered lacustrine core records as hemipelagically deposited, organic-rich, laminated diatomaceous oozes alternating with coarse tephra beds. The organic-rich oozes are characterized by low carbon and nitrogen stable-isotope values and occur in profundal areas of the modern lake floor. These sediments suggest an algae-dominated productivity regime and preservation of organic matter at depth. With no perennial streams entering June Lake, surface-sediment grain-size distribution and geochemistry are controlled by water depth and basin morphology. Additional modern facies types include poorly sorted coarse detrital landslide deposits below steep basin walls and volcaniclastic sandy gravel in windward littoral areas. These data provide a modern facies model for sedimentation in ice-scoured, hydrologically closed sub-alpine lakes and a baseline for future paleoclimate studies using June Lake sediment cores.
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Sabol, Martin, Diana Slyšková, Silvia Bodoriková, Tomáš Čejka, Andrej Čerňanský, Martin Ivanov, Peter Joniak, Marianna Kováčová und Csaba Tóth. „Revised floral and faunal assemblages from Late Pleistocene deposits of the Gánovce-Hrádok Neanderthal site – biostratigraphic and palaeoecological implications“. Fossil Imprint 73, Nr. 1-2 (15.08.2017): 182–96. http://dx.doi.org/10.2478/if-2017-0010.
Annotation:
Revisory research of floral and animal assemblages from the Neanderthal site of Gánovce-Hrádok confirmed the previous stratigraphic division of the travertine mound to five horizons on the basis of different petrological and palaeontological contents, indicating climatic and palaeoenvironmental changes in the vicinity, from the Saalian termination to the Holocene. At least two species of molluscs and approximately 20 taxa of vertebrates have been determined, and at least 8 endocasts of large mammals have been re-discovered. Revised floral record contained 570 specimens, but no more than 20% were suitable for taxonomic revision.
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Nabhan, Abdullah I., und Wan Yang. „Stratigraphic variability of Upper Holocene marginal marine sediments along the Al Qahmah Coast of Red Sea, Saudi Arabia“. Sedimentary Geology 433 (Mai 2022): 106134. http://dx.doi.org/10.1016/j.sedgeo.2022.106134.
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Su, Ming, Tiago M. Alves, Wei Li, Zhibin Sha, Kan-Hsi Hsiung, Jinqiang Liang, Zenggui Kuang, Nengyou Wu, Boda Zhang und Cheng-Shing Chiang. „Reassessing two contrasting Late Miocene-Holocene stratigraphic frameworks for the Pearl River Mouth Basin, northern South China Sea“. Marine and Petroleum Geology 102 (April 2019): 899–913. http://dx.doi.org/10.1016/j.marpetgeo.2018.12.034.
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Sweeney, Mark R., Eric V. McDonald, Lucas P. Chabela und Paul R. Hanson. „The role of eolian-fluvial interactions and dune dams in landscape change, late Pleistocene–Holocene, Mojave Desert, USA“. GSA Bulletin 132, Nr. 11-12 (02.04.2020): 2318–32. http://dx.doi.org/10.1130/b35434.1.
Annotation:
Abstract The formation of the Kelso Dunes in the eastern Mojave Desert, California, was a landscape-changing event triggered by an increase in sediment supply that followed the incision of Afton Canyon by the Mojave River ca. 25 ka. Eastward migration of sand dunes occurred along a well-defined eolian transport corridor. Dunes temporarily blocked washes resulting in substantial aggradation of eolian and fluvial sediments. Stratigraphic exposures reveal numerous fining-up sequences with interbedded eolian sands that provide evidence of dune dams and subsequent aggradation. Luminescence ages reveal that dune blocking and aggradation correspond to a regional pulse of alluvial fan sedimentation that occurred ca. 14–9 ka. Meanwhile, relative landscape stability occurred downstream of dune dams, resulting in the formation of a moderately developed soil on abandoned fluvial deposits. The next pulse of alluvial fan activity ca. 6–3 ka likely resulted in the breaching of the dune dams, followed by incision. Eolian system sediment state theory suggests that eolian activity in the Mojave Desert is closely tied to enhanced sediment supply, primarily related to the Mojave River–Lake Mojave system. Our data suggests that Intermittent Lake Mojave I, ca. 26–22 ka, triggered a large dune-building event that impounded massive amounts of sediment derived from alluvial fans deposited during the Pleistocene-Holocene transition. Breaching of dune dams and sediment recycling may have also increased sediment supply that contributed to late Holocene eolian activity. This profound impact on the regional geomorphology highlights the critical importance of eolian-fluvial interactions in desert environments.
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Elsheikh, Mahmoud. „Seismic Stratigraphic Analysis and Hydrocarbon Potential of Miocene-Quaternary Deposits in the Western Nile Delta Basin“. Iraqi Geological Journal 54, Nr. 2C (30.09.2021): 1–12. http://dx.doi.org/10.46717/igj.54.2c.1ms-2021-09-20.
Annotation:
This study focuses on the subsurface Miocene-Pleistocene sedimentary sequence of the Western Delta of Deep-Sea field. Analysis of seismic, based on obtainable well data, and seismic data, allows us to divide the studied successions into two mega sequences: Pre and Post Messinian complexes resulting in transgressive-regressive sedimentation cycles of sea level during the evolution of the Miocene-Pleistocene subsurface sedimentary sequence. The Relative level of the sea was extremely falling in the time of the Messinian period, although it was largely rising at the time of the lower to Middle Pliocene. Pre-Messinian complex encompasses the Miocene strata, while the Post-Messinian complex consists of a thickness pattern of deposits in the time of Pliocene to Pleistocene and ended up with Holocene. The comprehensive study presented here divides these complexes into several orders of sea-level cycles. Pre and Post-Messinian complexes are consisting of several third-order cycles, which is called a depositional sequence, hence the thickness pattern starts from Sidi Salem Formation and ends up with Mit Ghamr Formation (Pleistocene). The interpreted anticline represents a characteristic overlap that can create an appropriate structural trap for hydrocarbons in the sandy intermission of the formations of the Western Deep-Sea Delta field such as Kafr El Sheik siliceous clastic. Besides, the recognized individual and various hidden routes, such as channel and sub-channel in the Pre-Messinian complex are approved for additional inspection to discover hydrocarbons.
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Witter, Robert C., Adrian M. Bender, Katherine M. Scharer, Christopher B. DuRoss, Peter J. Haeussler und Richard O. Lease. „Geomorphic expression and slip rate of the Fairweather fault, southeast Alaska, and evidence for predecessors of the 1958 rupture“. Geosphere 17, Nr. 3 (06.05.2021): 711–38. http://dx.doi.org/10.1130/ges02299.1.
Annotation:
Abstract Active traces of the southern Fairweather fault were revealed by light detection and ranging (lidar) and show evidence for transpressional deformation between North America and the Yakutat block in southeast Alaska. We map the Holocene geomorphic expression of tectonic deformation along the southern 30 km of the Fairweather fault, which ruptured in the 1958 moment magnitude 7.8 earthquake. Digital maps of surficial geology, geomorphology, and active faults illustrate both strike-slip and dip-slip deformation styles within a 10°–30° double restraining bend where the southern Fairweather fault steps offshore to the Queen Charlotte fault. We measure offset landforms along the fault and calibrate legacy 14C data to reassess the rate of Holocene strike-slip motion (≥49 mm/yr), which corroborates published estimates that place most of the plate boundary motion on the Fairweather fault. Our slip-rate estimates allow a component of oblique-reverse motion to be accommodated by contractional structures west of the Fairweather fault consistent with geodetic block models. Stratigraphic and structural relations in hand-dug excavations across two active fault strands provide an incomplete paleoseismic record including evidence for up to six surface ruptures in the past 5600 years, and at least two to four events in the past 810 years. The incomplete record suggests an earthquake recurrence interval of ≥270 years—much longer than intervals <100 years implied by published slip rates and expected earthquake displacements. Our paleoseismic observations and map of active traces of the southern Fairweather fault illustrate the complexity of transpressional deformation and seismic potential along one of Earth's fastest strike-slip plate boundaries.
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SVEDHAGE, KRISTER. „Stratigraphic indications of a Pleistocene/Holocene transgression in the Göta ÁUlv river valley, SW Sweden“. Boreas 14, Nr. 1 (16.01.2008): 87–95. http://dx.doi.org/10.1111/j.1502-3885.1985.tb00892.x.
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Sincavage, Ryan, Paul M. Betka, Stuart N. Thomson, Leonardo Seeber, Michael Steckler und C. Zoramthara. „Neogene shallow-marine and fluvial sediment dispersal, burial, and exhumation in the ancestral Brahmaputra delta: Indo-Burman Ranges, India“. Journal of Sedimentary Research 90, Nr. 9 (01.09.2020): 1244–63. http://dx.doi.org/10.2110/jsr.2020.60.
Annotation:
ABSTRACT The stratigraphic record of Cenozoic uplift and denudation of the Himalayas is distributed across its peripheral foreland basins, as well as in the sediments of the Ganges–Brahmaputra Delta (GBD) and the Bengal–Nicobar Fan (BNF). Recent interrogation of Miocene–Quaternary sediments of the GBD and BNF advance our knowledge of Himalayan sediment dispersal and its relationship to regional tectonics and climate, but these studies are limited to IODP boreholes from the BNF (IODP 354 and 362, 2015-16) and Quaternary sediment cores from the GBD (NSF-PIRE: Life on a tectonically active delta, 2010-18). We examine a complementary yet understudied stratigraphic record of the Miocene–Pliocene ancestral Brahmaputra Delta in outcrops of the Indo-Burman Ranges fold–thrust belt (IBR) of eastern India. We present detailed lithofacies assemblages of Neogene delta plain (Tipam Group) and intertidal to upper-shelf (Surma Group) deposits of the IBR based on two ∼ 500 m stratigraphic sections. New detrital-apatite fission-track (dAFT) and (U-Th)/He (dAHe) dates from the Surma Group in the IBR help to constrain maximum depositional ages (MDA), thermal histories, and sediment accumulation rates. Three fluvial facies (F1–F3) and four shallow marine to intertidal facies (M1–M4) are delineated based on analog depositional environments of the Holocene–modern GBD. Unreset dAFT and dAHe ages constrain MDA to ∼ 9–11 Ma for the Surma Group, which is bracketed by intensification of turbidite deposition on the eastern BNF (∼ 13.5–6.8 Ma). Two dAHe samples yielded younger (∼ 3 Ma) reset ages that we interpret to record cooling from denudation following burial resetting due to a thicker (∼ 2.2–3.2 km) accumulation of sediments near the depocenter. Thermal modeling of the dAFT and dAHe results using QTQt and HeFTy suggest that late Miocene marginal marine sediment accumulation rates may have ranged from ∼ 0.9 to 1.1 mm/yr near the center of the paleodelta. Thermal modeling results imply postdepositional cooling beginning at ∼ 8–6.5 Ma, interpreted to record onset of exhumation associated with the advancing IBR fold belt. The timing of post-burial exhumation of the IBR strata is consistent with previously published constraints for the avulsion of the paleo-Brahmaputra to the west and a westward shift of turbidite deposition on the BNF that started at ∼ 6.8 Ma. Our results contextualize tectonic controls on basin history, creating a pathway for future investigations into autogenic and climatic drivers of behavior of fluvial systems that can be extracted from the stratigraphic record.
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Sarti, Giovanni, Veronica Rossi und Alessandro Amorosi. „Influence of Holocene stratigraphic architecture on ground surface settlements: A case study from the City of Pisa (Tuscany, Italy)“. Sedimentary Geology 281 (Dezember 2012): 75–87. http://dx.doi.org/10.1016/j.sedgeo.2012.08.008.
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Gentili, Bernardino, Gilberto Pambianchi, Domenico Aringoli, Marco Materazzi und Marco Giacopetti. „Pliocene –Pleistocene geomorphological evolution of the Adriatic side of Central Italy“. Geologica Carpathica 68, Nr. 1 (01.02.2017): 6–18. http://dx.doi.org/10.1515/geoca-2017-0001.
Annotation:
Abstract This work is a significant contribution to knowledge of the Quaternary and pre-Quaternary morphogenesis of a wide sector of central Italy, from the Apennine chain to the Adriatic Sea. The goal is achieved through a careful analysis and interpretation of stratigraphic and tectonic data relating to marine and continental sediments and, mostly, through the study of relict limbs of ancient landscapes (erosional surfaces shaped by prevailing planation processes). The most important scientific datum is the definition of the time span in which the modelling of the oldest morphological element (the “summit relict surface”) occurred: it started during Messinian in the westernmost portion and after a significant phase during middle-late Pliocene, ended in the early Pleistocene. During the middle and late Pleistocene, the rapid tectonic uplift of the area and the climate fluctuations favoured the deepening of the hydrographic network and the genesis of three orders of fluvial terraces, thus completing the fundamental features of the landscape. The subsequent Holocene evolution reshaped the minor elements, but not the basic ones.
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Arcusa, Stephanie H., Tobias Schneider, Pablo V. Mosquera, Hendrik Vogel, Darrell Kaufman, Sönke Szidat und Martin Grosjean. „Late Holocene tephrostratigraphy from Cajas National Park, southern Ecuador“. Andean Geology 47, Nr. 3 (30.09.2020): 508. http://dx.doi.org/10.5027/andgeov47n3-3301.
Annotation:
Lakes located downwind of active volcanoes serve as a natural repository for volcanic ash (tephra) produced during eruptive events. In this study, sediment cores from four lakes in Cajas National Park, southern Ecuador, situated approximately 200 km downwind of active volcanoes in the Northern Andes Volcanic Zone, were analysed to document the regional history of tephra fall extending back around 3,000 a cal BP. The ages of the lacustrine sedimentary sequences were constrained using a total of 20 AMS radiocarbon ages on plant remains. The tephra layers were correlated among the lakes based on their radiocarbon age, elemental composition, colour, and grain morphology. We found five unique tephra layers, each at least 0.2 cm thick, and further constrained their ages by combining the results from two age-depth modelling approaches (clam and rbacon). The tephra layers were deposited 3,034±621, 2,027±41, 1,557±177, 733±112, and 450±70 a cal BP. The ages of all but the youngest tephra layer overlap with those of known eruptions from Tungurahua. Some tephra layers are missing as macroscopic layers in several cores, with only two of the five tephra layers visible in the sediment of three lakes. Likewise, previous studies of lake sediment cores from the region are missing the four youngest tephra layers, further highlighting the need to sample multiple lakes to reconstruct a comprehensive history of fallout events. The newly documented stratigraphic marker layers will benefit future studies of lake sediments in Cajas National Park.
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Townsend, Kirk F., Michelle S. Nelson, Tammy M. Rittenour und Joel L. Pederson. „Anatomy and evolution of a dynamic arroyo system, Kanab Creek, southern Utah, USA“. GSA Bulletin 131, Nr. 11-12 (02.05.2019): 2094–109. http://dx.doi.org/10.1130/b35195.1.
Annotation:
Abstract Many alluvial valleys in the American Southwest are entrenched within continuous arroyos, and stratigraphic evidence indicates that these fluvial systems experienced repeated periods of entrenchment and aggradation during the mid- to late-Holocene. Previous research suggests arroyo dynamics were regionally quasi-synchronous, implying that they were driven by allogenic forcing due to hydroclimatic fluctuations. However, several of these interpretations rely on records with limited age control and include distal correlations across the American Southwest. While hydroclimatic variability must exert some role, autogenic mechanisms related to catchment-specific geomorphic thresholds are hypothesized to partially control the timing of arroyo dynamics. If driven by autogenic processes, episodes of arroyo cutting and filling may not be regionally contemporaneous. Recent improvements in dating methods permit more detailed reconstructions of the timing and evolution of arroyo dynamics, allowing for a more nuanced assessment of these competing hypotheses. Here we present a uniquely large and focused chronostratigraphic data set from two alluvial reaches of Kanab Creek, located in the Grand Staircase region of southern Utah. Episodes of prehistoric arroyo cutting and filling are reconstructed from 27 sites through recognition of soils and buttressed unconformities in the arroyo-wall stratigraphy, and age control derived from 54 optically stimulated luminescence (OSL) ages and 50 radiocarbon ages. Our chronostratigraphic data set indicates five periods of channel aggradation occurred since ca. 6.0 ka, with each interrupted by an episode of arroyo entrenchment. Repeated aggradation to a similar channel elevation suggests attainment of a threshold profile, and comparison of the pre-entrenchment longitudinal profile with the modern arroyo channel demonstrates that changes between end-member entrenched and aggraded states are expressed in channel concavity and slope. We propose that arroyo dynamics are partially driven by sediment supply and the rate of channel aggradation, and that these systems must approach complete re-filling before they become sensitive to incision. Entrenchment itself appears to be associated with rapid transitions from pronounced decadal-scale aridity to pluvial (wetter) periods. Not all such hydroclimatic fluctuations are associated with arroyo entrenchment, which highlights the importance of threshold controls on the behavior of these systems. The collective period of “dynamic instability” characterized by epicycles of arroyo entrenchment and aggradation did not initiate until the mid-Holocene, when a climatic shift toward warmer and drier conditions likely increased fine-grained sediment supply to the fluvial system.
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Tamura, T. „Preservation and Grain-Size Trends of Holocene Wave-Dominated Facies Successions in Eastern Japan: Implications for High-Resolution Sequence Stratigraphic Analysis“. Journal of Sedimentary Research 74, Nr. 5 (01.09.2004): 718–29. http://dx.doi.org/10.1306/021304740718.
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WILSON, BRENT. „The significance of iron-stained foraminifera off SE Trinidad, West Indies, western central Atlantic Ocean“. Geological Magazine 147, Nr. 5 (10.02.2010): 728–36. http://dx.doi.org/10.1017/s0016756810000026.
Annotation:
AbstractEleven samples of seafloor sediment were taken from water depths of 78–90 m within the Savonette Field, off SE Trinidad, western Atlantic Ocean. This surface sediment is relict, having been deposited during an early Holocene transgression. The samples yielded much iron-stained quartz and a rich assemblage of dead foraminifera, of which 75% of planktonic foraminifera were stained with iron, as was 66.5% of the calcareous benthonic foraminiferal assemblage. The fauna, both iron-stained and unstained, was dominated by Cibicidoides ex. gr. pseudoungerianus, and is concluded, despite the proximity of the Orinoco Delta, to be equivalent to a relict Cibicidoides biofacies in carbonate-rich areas of the Gulf of Mexico. Staining was by limonite and hematite. Differing percentages of calcareous benthonic species had been stained with iron, ANOVA revealing three groups of species within which the mean percentage of iron-stained specimens per sample did not differ: (a) Globocassidulina subglobosa and Hanzawaia concentrica; (b) Amphistegina gibbosa, Cassidulina norcrossi australis Cibicioides ex. gr. pseudoungerianus, C. io, Elphidium translucens and Quinqueloculina lamarckiana; and (c) Eponides antillarum and E. repandus. It is concluded that species differ in their susceptibility to iron staining, and that planktonic foraminifera are more susceptible than most benthonic species. Although waters off northern South America are turbid and the photic zone only ~25 m deep, the relict assemblage contained 8.4% algal symbiont-bearing foraminifera (especially A. gibbosa and E. translucens) that would be limited to the photic zone. These are thought to have lived at a time early in the Holocene transgression when sequestration of sediment within the Orinoco delta rendered the water sufficiently clear for viable populations of symbiont-bearing foraminifera. Should iron-stained foraminifera prove to be restricted to transgressive systems tracts, this would make them a useful sequence stratigraphic tool.
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CORDANI, UMBERTO G., ANA M. MIZUSAKI, KOJI KAWASHITA und ANTONIO THOMAZ-FILHO. „Rb–Sr systematics of Holocene pelitic sediments and their bearing on whole-rock dating“. Geological Magazine 141, Nr. 2 (März 2004): 233–44. http://dx.doi.org/10.1017/s0016756803008616.
Annotation:
In many cases, when dealing with argillaceous fine-grained sedimentary rocks, the isotopic ages obtained from Rb–Sr whole-rock isochron calculations are of geological significance, despite the fact that the initial conditions of Sr isotopic homogenization are not fulfilled. To explain this, a mechanical mixing during deposition has been suggested, leading to an aggregate of mixed material with fairly uniform 87Sr/86Sr values, whatever Rb/Sr ratio is found in the analysed samples. This investigation of the behaviour of Rb and Sr during sedimentation and early diagenesis, involves study of more than 60 samples of fine-grained recent sediments from selected coastal localities of Brazil. The results indicate that pelitic samples from some recent to present-day transitional or shallow marine environments, such as the Jacarepaguá tidal flat and the Amazonas River mouth, where halmirolysis could have occurred, may produce nearly horizontal best-fit lines in a Rb–Sr isochron diagram. Moreover, the initial isotopic 87Sr/86Sr ratios appear to be well above 0.710. In open marine environments, such as the Campos Basin, where sampling was spread over more than 100 metres, exchanges between the argillaceous sediments and seawater potentially happen at low temperature, inducing a reduction of the 87Sr/86Sr isotopic composition of the sediments to nearly 0.710. An almost horizontal best-fit line is produced for the entire stratigraphic section, independent of the sedimentation age. We believe that in similar environments such ‘zero age isochrons’ are maintained for some time, testifying to exchanges between the sediment and the interstitial fluids, before the onset of burial diagenesis. The above described studies on fine-grained and recent argillaceous sediments seem to confirm the production of horizontal best-fit lines in isochron diagrams, justifying the application of the Rb–Sr whole-rock method to pelitic sedimentary rocks. The nature of the material is critical. The pelitic sediments to be analysed should contain only very limited amounts of coarse clastic material (especially feldspars and mica fragments) and consist mainly of fine clay minerals in which smectites, illite and mixed layers illite–smectite largely predominate.
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Liang, Xia, Xiaopeng Dong, Jiyuan Yan und Xiaobo Liu. „Holocene stratigraphic sequences in the northern Ordos Plateau and its implications for the disappearance of Huoluochaideng ancient city in the Han Dynasty, North China“. Geological Journal 55, Nr. 11 (03.09.2020): 7400–7414. http://dx.doi.org/10.1002/gj.3966.
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Sanders, Diethard. „Rocky shore-gravelly beach transition, and storm/post-storm changes of a holocene gravelly beach (Kos island, Aegean sea): Stratigraphic significance“. Facies 42, Nr. 1 (Januar 2000): 227–43. http://dx.doi.org/10.1007/bf02562574.
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Williams, Martin. „When the Land Sings: Reconstructing Prehistoric Environments Using Evidence from Quaternary Geology and Geomorphology, with Examples Drawn from Fluvial Environments in the Nile and Son Valleys“. Quaternary 5, Nr. 3 (18.07.2022): 32. http://dx.doi.org/10.3390/quat5030032.
Annotation:
Geomorphic evidence from rivers and lakes can help explain past changes in the locations of archaeological sites as well as environmental and climatic changes in their catchment areas. Examples drawn from the Blue and White Nile valleys in northeast Africa and from the Son and Belan valleys in north-central India reveal how Quaternary climatic fluctuations in the headwaters of these rivers are reflected in changes in river channel patterns downstream as well as in the type of sediment transported. Soils and sediments that contain prehistoric and historic artefacts can be analysed to show the type of environment in which the artefacts accumulated. Beds of volcanic ash may preserve former landscapes and their fossil remains and can provide a synchronous time marker against which to assess changes in the archaeological record. The pattern and tempo of past sea level fluctuations has controlled the distribution of coastal archaeological sites and helps to explain the absence of certain Holocene Neolithic sites in southeast Asia. Disturbance of archaeological sites by plants and animals, especially termites in tropical regions, can affect the stratigraphic and chronological integrity of the site.
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Şengül, M. Alper, Şule Gürboğa, İsmail Akkaya und Ali Özvan. „Deformation patterns in the Van region (Eastern Turkey) and their significance for the tectonic framework“. Geologica Carpathica 70, Nr. 3 (01.06.2019): 193–208. http://dx.doi.org/10.2478/geoca-2019-0011.
Annotation:
Abstract The area of investigation is located on the south-eastern shore of Lake Van in Eastern Turkey where a destructive earthquake took place on 23rd October, 2011 (Mw = 7.1). Following the earthquake, different source mechanisms, deformations, and types of faulting have been suggested by different scientists. In this research, Edremit district and vicinities located on the southern side of Van have been investigated to understand the deformation pattern in a travertine (400 ka) formation on the surface, and its structural and stratigraphic relationships with the main faults under the surface by using two-dimensional (2D) Electrical Resistivity Tomography (ERT) profiles. The results were used to document the deformation pattern of rocks with the Miocene and the Holocene (400 ka travertine) in ages. By means of the investigations, deformation patterns implying the tectonic regimes during the Oligocene–Miocene–Pliocene, and Quaternary time have been determined. According to detailed field work, the local principal stress direction has been defined as approximately N 35° W. This is also supported by the joint set and slip-plane data. Moreover, Oligocene– Miocene units provide a similar principal stress direction. Our data suggest that the southern part of the Elmalık fault is characteristic of reverse faults rather than of the normal fault system that has been previously reported. In addition, the Gürpınar fault controlling the deformation patterns of the region is a reverse fault with dextral component.
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Chang, Tae Soo, Burghard W. Flemming, Elke Tilch, Alexander Bartholomä und Ralf Wöstmann. „Late Holocene stratigraphic evolution of a back-barrier tidal basin in the East Frisian Wadden Sea, southern North Sea: transgressive deposition and its preservation potential“. Facies 52, Nr. 3 (18.07.2006): 329–40. http://dx.doi.org/10.1007/s10347-006-0080-2.
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Schwab, William C., Wayne E. Baldwin, Jane F. Denny, Cheryl J. Hapke, Paul T. Gayes, Jeffrey H. List und John C. Warner. „Modification of the Quaternary stratigraphic framework of the inner-continental shelf by Holocene marine transgression: An example offshore of Fire Island, New York“. Marine Geology 355 (September 2014): 346–60. http://dx.doi.org/10.1016/j.margeo.2014.06.011.
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Dill, Harald G., Sobhi Nasir und Hamad Al-Saad. „Lithological and structural evolution of the northern sector of Dukhan anticline, Qatar, during the early Tertiary: with special reference to sequence stratigraphic bounding surfaces“. GeoArabia 8, Nr. 2 (01.04.2003): 201–26. http://dx.doi.org/10.2113/geoarabia0802201.
Annotation:
ABSTRACT Early Tertiary sediments are widely exposed in Qatar and only in coastal areas and a few places inland do Holocene deposits mask them. The variable resistance to weathering of the Tertiary sediments is responsible for the general low-relief landscape interspersed with flat-topped hills, the most prominent of which are in western Qatar where they are the surface expression of the Dukhan anticline. The early Tertiary was a time of shallow-marine sedimentation and several transgressive and regressive cycles occurred. Sedimentation began on a dolomitic carbonate shelf, which gave way to a mixed carbonate-siliciclastic shelf that became increasingly calcitic. Coarsening-upward sequences with fine-grained muddy sediments at the base and grainstones and boundstones on top attested to a cyclic change in the energy regime. Small-scale cycles and major unconformities resulted from eustatic sea-level changes. In the Dukhan study area, the most prominent sequence boundary was near the Ypresian-Lutetian boundary. Following this hiatus, a Lutetian transgressive system tract evolved that was terminated by a maximum flooding surface correlated with the named MFS Pg20. Minor unconformities and NE-trending faults of post-Miocene age resulted from the interplay of local diapiric salt movements in the Dukhan anticline and a regionally changing stress field. Extensional faulting was succeeded by a compressional phase that caused the reactivation of some normal faults as steeply dipping reverse faults. Diagenetic processes and the pervasive etching of the landscape formed ferrous, siliceous, and gypsiferous duricrusts. Phosphate was reworked and concentrated above the Ypresian-Lutetian unconformity. Ferricretes were derived from iron-bearing phyllosilicates and disulfides. Ferric iron-oxide hydrates were the result of oxidizing conditions but their parent material furnished evidence of less-oxygenated conditions and a rising sea level during the Lutetian transgression. The studies provided information on the economic potential of aggregates, clay, hydraulic binders, and building stones, and the prediction of subsidence-prone areas.
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Crow, Ryan S., Keith A. Howard, L. Sue Beard, Philip A. Pearthree, P. Kyle House, Karl E. Karlstrom, Lisa Peters et al. „Insights into post-Miocene uplift of the western margin of the Colorado Plateau from the stratigraphic record of the lower Colorado River“. Geosphere 15, Nr. 6 (16.10.2019): 1826–45. http://dx.doi.org/10.1130/ges02020.1.
Annotation:
Abstract The spatial and temporal distribution of Pliocene to Holocene Colorado River deposits (southwestern USA and northwestern Mexico) form a primary data set that records the evolution of a continental-scale river system and helps to delineate and quantify the magnitude of regional deformation. We focus in particular on the age and distribution of ancestral Colorado River deposits from field observations, geologic mapping, and subsurface studies in the area downstream from Grand Canyon (Arizona, USA). A new 4.73 ± 0.17 Ma age is reported for a basalt that flowed down Grand Wash to near its confluence with the Colorado River at the eastern end of what is now Lake Mead (Arizona and Nevada). That basalt flow, which caps tributary gravels, another previously dated 4.49 ± 0.46 Ma basalt flow that caps Colorado River gravel nearby, and previously dated speleothems (2.17 ± 0.34 and 3.87 ± 0.1 Ma) in western Grand Canyon allow for the calculation of long-term incision rates. Those rates are ∼90 m/Ma in western Grand Canyon and ∼18–64 m/Ma in the eastern Lake Mead area. In western Lake Mead and downstream, the base of 4.5–3.5 Ma ancestral Colorado River deposits, called the Bullhead Alluvium, is generally preserved below river level, suggesting little if any bedrock incision since deposition. Paleoprofiles reconstructed using ancestral river deposits indicate that the lower Colorado River established a smooth profile that has been graded to near sea level since ca. 4.5 Ma. Steady incision rates in western Grand Canyon over the past 0.6–4 Ma also suggest that the lower Colorado River has remained in a quasi–steady state for millions of years with respect to bedrock incision. Differential incision between the lower Colorado River corridor and western Grand Canyon is best explained by differential uplift across the Lake Mead region, as the overall 4.5 Ma profile of the Colorado River remains graded to Pliocene sea level, suggesting little regional subsidence or uplift. Cumulative estimates of ca. 4 Ma offsets across faults in the Lake Mead region are similar in magnitude to the differential incision across the area during the same approximate time frame. This suggests that in the past ∼4 Ma, vertical deformation in the Lake Mead area has been localized along faults, which may be a surficial response to more deep-seated processes. Together these data sets suggest ∼140–370 m of uplift in the past 2–4 Ma across the Lake Mead region.