Depositional environment and OSL chronology of the Homeb silt deposits, Kuiseb River, Namibia

AbstractPrevious studies suggest that the Homeb silts of the Kuiseb valley, Namibia (i) accumulated in a dune-dammed lake, (ii) are end-point deposits, (iii) represent an aggrading river bed, and (iv) are slackwater deposits. Thus, they have been used alternatively as evidence of past drier conditions or past wetter conditions. Lithostratigraphic analysis of two sediment sequences at Homeb indicates sedimentation by aggradation of the Kuiseb River triggered by a transition from an arid to humid climate. OSL ages for the sequences were obtained by the SAR protocol on aliquots of 9.6-mm and 4.0-mm diameter and on single grains. Four-millimeter aliquot minimum ages closely approximate the single-grain minimum ages and are younger than 9.6-mm aliquot minimum and central ages. Based on these results, the small-aliquot (4-mm) approach appears to provide ages comparable to those obtained by the more laborious and time-consuming single-grain method. Minimum ages indicate rapid deposition of the Homeb Silts in at least two episodes centered at ∼15 ka and ∼6 ka during climate transitions from arid to humid. Flash floods eroded the valley fills during slightly more arid conditions.

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Sedimentology and geochemistry of Middle–Upper Permian in northwestern Turpan–Hami Basin, China: Implication for depositional environments and petroleum geology

Energy Exploration & Exploitation ◽

10.1177/0144598718779100 ◽

2018 ◽

Vol 36 (4) ◽

pp. 910-941

Author(s):

Jian Song ◽

Zhidong Bao ◽

Xingmin Zhao ◽

Yinshan Gao ◽

Xinmin Song ◽

...

Keyword(s):

Depositional Environment ◽

Saline Water ◽

Depositional Environments ◽

Source Rocks ◽

Petroleum Exploration ◽

Upper Permian ◽

Late Permian ◽

Humid Climate ◽

Mountain Area ◽

Volcanic Source

Studies have found that the Permian is another important stratum for petroleum exploration except the Jurassic coal measures within Turpan–Hami Basin recently. However, the knowledge of the depositional environments and its petroleum geological significances during the Middle–Late Permian is still limited. Based on the analysis about the sedimentological features of the outcrop and the geochemical characteristics of mudstones from the Middle Permian Taerlang Formation and Upper Permian Quanzijie Formation in the Taoshuyuanzi profile, northwest Turpan–Hami Basin, this paper makes a detailed discussion on the Middle–Late Permian paleoenvironment and its petroleum geological significances. The Middle–Upper Permian delta–lacustrine depositional system was characterized by complex vertical lithofacies assemblages, which were primarily influenced by tectonism and frequent lake-level variations in this area. The Taerlang Formation showed a significant lake transgression trend, whereas the regressive trend of the Quanzijie Formation was relatively weaker. The provenance of Taerlang and Quanzijie Formations was derived from the rift shoulder (Bogda Mountain area now) to the north and might be composed of a mixture of andesite and felsic volcanic source rocks. The Lower Taerlang Formation was deposited in a relatively hot–dry climate, whereas the Upper Taerlang and Quanzijie Formations were deposited in a relatively humid climate. During the Middle–Late Permian, this area belonged to an overall semi-saline water depositional environment. The paleosalinity values showed stepwise decreases from the Lower Taerlang Formation to the Upper Quanzijie Formation, which was influenced by the changes of paleoclimate in this region. During the Middle–Late Permian, the study area was in an overall anoxic depositional environment. The paleoenvironment with humid climate, lower paleosalinity, anoxic condition, and semi-deep to deep water during the deposition of the Upper Taerlang Formation was suitable for the accumulation of mudstones with higher TOC values.

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Small aliquot and single grain IRSL and post-IR IRSL dating of fluvial and alluvial sediments from the Pativilca valley, Peru

Quaternary Geochronology ◽

10.1016/j.quageo.2013.12.004 ◽

2014 ◽

Vol 22 ◽

pp. 163-174 ◽

Cited By ~ 39

Author(s):

Mareike Trauerstein ◽

Sally E. Lowick ◽

Frank Preusser ◽

Fritz Schlunegger

Keyword(s):

Alluvial Sediments ◽

Single Grain ◽

Small Aliquot

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The diagenesis of the Lower Triassic Bunter Sandstone Formation, Onshore Denmark

Danmarks Geologiske Undersøgelse Serie A ◽

10.34194/seriea.v15.7034 ◽

1986 ◽

Vol 15 ◽

pp. 1-51

Author(s):

Stanley Fine

Keyword(s):

Late Stage ◽

Depositional Environment ◽

Sedimentary Facies ◽

Lower Triassic ◽

Low Energy ◽

Ti Oxides ◽

Arid Conditions ◽

Sandstone Formation ◽

Diagenetic Evolution ◽

Semi Arid

The Lower Triassic Bunter Sandstone Formation is a continental redbed sequence deposited under arid to semi-arid conditions in a low-energy, fluviatile-aeolian sabhka environment. The sediments display many diagenetic features in common with modern and ancient redbeds deposited under similar conditions, but local influences on the diagenetic assemblage by factors such as provenance, structural setting and depositional environment can be ascertained. With burial depths of only 1000-2000 meters, effects of compaction are limited, high intergranular porosities remain, and no clear depth-related patterns are noted. The diagenetic assemblage consists of quartz and feldspar overgrowths, Fe-Ti oxides, carbonates (calcite and dolomite), analcime, authigenic clays, anhydrite and halite. The distribution of authigenic minerals is controlled by sedimentary facies, with greater amounts of poikilotopic anhydrite and halite in sandstones and more abundant dolomite and analcime in claystones and heterolithic sands. In addition, the replacement of ferromagnesian minerals by mixed-layer clays results in the greater abundance of these clays in sandstones relative to claystones. A well-preserved eogenetic assemblage consisting of albite and quartz overgrowths, analcime, dolomite, calcite, gypsum and clays is indicative of highly evaporative conditions and may reflect higher sodium concentrations in the depositional brines associated with the more basinal, low-energy parts of the depositional environment. Such concentrated brines strongly influenced the diagenetic pathways. In contrast, anhydrite and halite are the product of mesogenetic reactions in association with late stage Zechstein brines which invaded the more permeable sands during halokinesis. The strength and character of the depositional brine is an early control on subsequent diagenetic evolution. Within the specific geochemical regime of a given lithofacies, selective reactions occur which characterize particular microenvironments. These reactions impart an early eogenetic imprint upon later diagenetic events.

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Testing the suitability of dim sedimentary quartz from northern Switzerland for OSL burial dose estimation

Geochronometria ◽

10.1515/geochr-2015-0058 ◽

2017 ◽

Vol 44 (1) ◽

pp. 66-76 ◽

Cited By ~ 13

Author(s):

Mareike Trauerstein ◽

Sally E. Lowick ◽

Frank Preusser ◽

Heinz Veit

Keyword(s):

Slow Component ◽

Data Set ◽

Northern Switzerland ◽

Signal Characteristics ◽

Wide Range ◽

Single Grain ◽

Small Aliquot ◽

Range Of Values ◽

Isothermal Decay ◽

Partial Bleaching

Abstract We investigate the suitability of sedimentary quartz associated with former glacial advances in northern Switzerland to provide reliable burial dose estimates using Optically Stimulated Luminescence (OSL). Previous studies on northern alpine quartz show that its signal characteristics can be poor and potentially problematic. We analyse quartz signals of small aliquots, which reveal the presence of a prominent medium or slow component in the initial part of some signals. Nonetheless, rejection of aliquots with unfavourable signal composition does not alter the burial dose estimates, but significantly reduces the data set for De determination. Signal lifetimes from isothermal decay measurements cover a wide range of values, yet the lowest lifetimes are high enough to guarantee a reliable burial dose estimate for samples of < 400 ka. Comparison of small aliquot and single grain burial dose distributions reveals that signal averaging masks partial bleaching in some of the samples. We therefore strongly recommend single grain measurements for samples from this setting and area, in order to exclude age overestimation due to partial bleaching.

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Flash-floods control

Periódico Eletrônico Fórum Ambiental da Alta Paulista ◽

10.17271/1980082717220212977 ◽

2021 ◽

Vol 17 (2) ◽

Author(s):

Emerson Luís Pawoski da Silva ◽

Maria Helena de Carvalho Rodrigues Silva ◽

Francisco de Assis Mendonça

Keyword(s):

Land Cover ◽

Meteorological Data ◽

Mass Movement ◽

Flash Floods ◽

Civil Defense ◽

Humid Climate ◽

Future Scenario ◽

Rugged Terrain ◽

Legal Provisions ◽

Risk Areas

Flash-Floods are among the hydrological disasters that most damage life and structures in Brazil. The frequency and impacts of flash-floods may become an increasing problem due to the future scenario of an increase in global temperature causing intense precipitation. Through the literature, the aim of this study was: clarify how flash-floods occur; present national policies and legal provisions related to disaster risk management and what actions are suggested for prevention and response. Flash-floods are intense water superficial movements that are not dependent on watercourses. They are depending of warm and humid climate, rugged terrain and waterproofing land cover. All over the planet, actions are proposed for these disasters. In Brazil, Civil Defense acts through monitoring, diagnosis, prognosis and structural actions, i.e., physical, and non-structural, or regulatory. The structural actions to flash-floods are focused on land cover and mainly vegetation, while non-structural actions focus on zoning risk areas and assisting of affected populations. These measurements can be improved with social data, as income, and meteorological data, as air mass movement, temperature, humidity and clouds. Information about flash-floods, responsible agencies and measures can be used to help manage the risk of these disasters.

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Holocene Paleohydrology of the St. Elias Mountains, British Columbia and Yukon

Géographie physique et Quaternaire ◽

10.7202/032622ar ◽

2007 ◽

Vol 40 (1) ◽

pp. 47-53 ◽

Cited By ~ 4

Author(s):

Peter G. Johnson

Keyword(s):

British Columbia ◽

Sediment Transport ◽

Depositional Environment ◽

Temporal Changes ◽

The Holocene ◽

Lake Formation ◽

Valley Side ◽

Dammed Lake ◽

Fluctuation Model ◽

Talus Deposits

ABSTRACT The evolution of the Holocene paraglacial environment of the St. Elias Mountains has been dominated by hydrological variations which modify the direct glacial depositional environment and trigger instabilities in valley side glacial and talus deposits. Data from the Kaskawulsh Glacier demonstrate how discharge and sediment transport regimes vary through the season, as sediment is flushed out of the system, and a marginal to subglacial drainage change of the Grizzly Creek Glacier illustrates the effects of extraordinary events in transporting large volumes of sediment. A multiple glacier fluctuation model applied to the region produces rapid temporal changes in discharge and sediment regimes throughout the Holocene. The effect of these variations is enhanced by the occurrence of surges of many of the glaciers of the St. Elias Mountains and by sequences of glacier dammed lake formation and drainage in the region.

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Increased fluvial runoff terminated inorganic aragonite precipitation on the Northwest Shelf of Australia during the early Holocene

Scientific Reports ◽

10.1038/s41598-019-54981-7 ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 2

Author(s):

Maximilian Hallenberger ◽

Lars Reuning ◽

Stephen J. Gallagher ◽

Stefan Back ◽

Takeshige Ishiwa ◽

...

Keyword(s):

Hydrological Cycle ◽

Ocean Water ◽

Pronounced Change ◽

Humid Climate ◽

Proxy Data ◽

Carbonate Sedimentation ◽

Arid Conditions ◽

Common Process ◽

Geochemical Analyses ◽

Inorganic Precipitation

AbstractInorganic precipitation of aragonite is a common process within tropical carbonate environments. Across the Northwest Shelf of Australia (NWS) such precipitates were abundant in the late Pleistocene, whereas present-day sedimentation is dominated by calcitic bioclasts. This study presents sedimentological and geochemical analyses of core data retrieved from the upper 13 meters of IODP Site U1461 that provide a high-resolution sedimentary record of the last ~15 thousand years. Sediments that formed from 15 to 10.1 ka BP are aragonitic and characterised by small needles (<5 µm) and ooids. XRF elemental proxy data indicate that these sediments developed under arid conditions in which high marine alkalinity favoured carbonate precipitation. A pronounced change of XRF-proxy values around 10.1 ka BP indicates a transition to a more humid climate and elevated fluvial runoff. This climatic change coincides with a shelf-wide cessation of inorganic aragonite production and a switch to carbonate sedimentation dominated by skeletal calcite. High ocean water alkalinity due to an arid climate and low fluvial runoff therefore seems to be a prerequisite for the formation of shallow water aragonite-rich sediments on the NWS. These conditions are not necessarily synchronous to interglacial periods, but are linked to the regional hydrological cycle.

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Geochemistry, Depositional and Tectonic setting of the Barail Group of the Indo-Myanmar Ranges

Indian Association of Sedimentologists ◽

10.51710/jias.v38i1.103 ◽

2021 ◽

Vol 38 (1) ◽

pp. 13-22

Author(s):

Salam Ranjeeta Devi

Keyword(s):

Continental Margin ◽

Chemical Weathering ◽

Depositional Environment ◽

Tectonic Setting ◽

Active Continental Margin ◽

Source Rocks ◽

Humid Climate ◽

Geochemical Study ◽

High Degree ◽

Semi Arid

The present paper deals with the study of the depositional environment and tectonic setting during the sedimentation of the Barail Group of rocks of the Indo-Myanmar Ranges (IMR). The Barail Group (Oligocene) consist of sandstone intercalated with shale and siltstone. Geochemical study suggests low to high degree of chemical weathering. ICV vs. CIA, Al2O3 vs. TiO2 diagrams indicate that the sediments were derived from the multiple source rocks dominantly of mafic composition. Arid to semi-arid/semi-humid climate prevailed during the deposition of the Barail Group sediments. Sedimentation occurred in a tectonic setting of overlap of passive to active continental margin under marine environment.

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