Contributors: Pratima M. Kessarkar, V. Purnachandra Rao, S.M. Ahmad, S.K. Patil, A. Anil Kumar, G. Anil Babu, Sukalyan Chakraborty, R. Soundar Rajan

Date: 2005-09-01

sediment cores used in this study ...sediments compared to unit 1 in both the cores. The unit 2 sediments represent...sediments in core 1 (SK148/2) ...Details of sediment cores used in this study ...sediment at different intervals of cores 1 and 2 ...sediments are predominantly olive black/grey in colour with abundant finer...sediments recovered from two gravity cores of the lower and distal Bengal...concentrations of sediment samples (core 1 and 2) together with the reported...Late Quaternary...Late Quaternary...sediment core SK148/2. OB—olive black, MB—moderate brown. (B) Downcore...sediments are calcareous pelagic sediments, which started depositing ∼...63μm size) of the sediment in core SK148/2. (Aa) and (Ab) show the grain...sediments in core SK148/2 (A), and in AAS37/2 (B). ...keels—K)) in sediment core AAS37/2. OG—olive grey, YB—yellowish brown,...Late Quaternary: Sedimentological and isotopic evidence from the distal...sediments...sediment deposition by turbidity current activity ceased in the distal...core exhibits two distinct units, the lower unit 2 and upper unit 1 sediments...the sediments in core 1 (SK148/2) ... The sediments recovered from two gravity cores of the lower and distal Bengal Fan were investigated for sedimentological properties and Sr–Nd isotopes. Each core exhibits two distinct units, the lower unit 2 and upper unit 1 sediments. The unit 2 sediments are predominantly olive black/grey in colour with abundant finer silt-size fractions, low organic carbon and CaCO3, quartz and mica in the coarse fraction, dominant illite and chlorite in the <2μm fraction and uniform rock-magnetic properties. Biogenic constituents are extremely rare or restricted to the lower part of unit 2. The unit 1 sediments, on the other hand, are moderate brown/yellowish brown in colour with intermittent thin dark-coloured sediment layers. Higher clay, organic carbon, CaCO3, and biogenic constituents in the coarse fraction, and enriched smectite and kaolinite in the <2μm fraction are typical. Magnetic susceptibility values are higher and correlate well with acid-insoluble residue content. Higher Rb, Sr, Sm and Nd concentrations, 87Sr/86Sr ratios and more radiogenic εNd values are characteristic for unit 2 sediments compared to unit 1 in both the cores. The unit 2 sediments represent Pleistocene hemiturbidites, older than 1314CkyrBP with their source from the northern Bay of Bengal (NBOB), derived from the Himalayas and transported by the Ganges–Brahmaputra (G–B) River system. Unit 1 sediments are calcareous pelagic sediments, which started depositing ∼1214CkyrBP, with its clastic sediments derived from the Himalayas and SE Indian/Sri Lankan margins. The change in lithofacies from unit 2 to unit 1 suggests that the sediment deposition by turbidity current activity ceased in the distal Bengal Fan at ∼1214CkyrBP, perhaps because of the rapid rise in sea-level during the melt water pulse 1A and Holocene.

Contributors: R. Klöcker, R. Henrich

Date: 2006-09-20

Late Quaternary high-sedimentation rate core (573 m water depth, Pakistan...Late Quaternary high-sedimentation rate core (573 m water depth, Pakistan...core 137KA is indicated by a star. ...core 137KA indicating organic and carbonate productivity (modified after...transect) and core SO90 137KA off Pakistan. ...sediments, light grey=indistinctly laminated sediments, white=bioturbated...sediment samples showing good to very good preservation (LDX: 2.2 to 1.3...Late Quaternary...Late Quaternary...of core 137KA is indicated by a star. ...core SO90 137KA off Pakistan. ...Late Quaternary pteropod preservation on the Pakistan shelf and continental...sediment core 137KA off Pakistan: (a) present-day situation with shallow...in sediment core 137KA off Pakistan: (a) present-day situation with shallow...sediment samples from the Pakistan shelf and upper continental slope and ... Fifteen surface sediment samples from the Pakistan shelf and upper continental slope and a Late Quaternary high-sedimentation rate core (573 m water depth, Pakistan continental margin) have been analysed to improve the understanding of the factors influencing pteropod preservation. The aragonite compensation depth (ACD) is located at 250–400 m water depth, which corroborates previous observations of a very shallow ACD in the northern Arabian Sea. With the exception of the Hab transect off Karachi, the ACD coincides with the upper boundary of the OMZ located at 250 m water depth. The shell preservation index of the pteropod Limacina inflata (LDX) was applied on six surface sediment samples showing good to very good preservation (LDX: 2.2 to 1.3).

Contributors: Patrick T. Moss, John Tibby, Lynda Petherick, Hamish McGowan, Cameron Barr

Date: 2013-08-05

of the cores. NC is the code for the samples taken from Native Companion...Late Quaternary climate dynamics...sediment core with black representing peat sediments, brown reflecting... the sediment core with black representing peat sediments, brown reflecting...late Quaternary palaeoenvironmental variability available from the subtropics...sediment core with black representing peat sediments and yellow reflecting...Late Quaternary vegetation history of North Stradbroke Island, Queensland...cores. NC is the code for the samples taken from Native Companion Lagoon...Late Quaternary climate dynamics...late Quaternary palaeoenvironmental variability available from the subtropics...late deglacial of Reeves et al. (2013a) have been combined into the LGIT...and late deglacial of Reeves et al. (2013a) have been combined into the...sediments...lithology of the sediment core with black representing peat sediments ... Currently there is a paucity of records of late Quaternary palaeoenvironmental variability available from the subtropics of Australia. The three continuous palaeoecological records presented here, from North Stradbroke Island, subtropical Queensland, assist in bridging this large spatial gap in the current state of knowledge. The dominance of arboreal taxa in the pollen records throughout the past >40,000 years is in contrast with the majority of records from temperate Australia, and indicates a positive moisture balance for North Stradbroke Island. The charcoal records show considerable inter-site variability indicating the importance of local-scale events on individual records, and highlighting the caution that needs to be applied when interpreting a single site as a regional record. The variability in the burning regimes is interpreted as being influenced by both climatic and human factors. Despite this inter-site variability, broad environmental trends are identifiable, with changes in the three records comparable with the OZ-INTIMATE climate synthesis for the last 35,000 years.

Contributors: M.B.L. Mascarenhas-Pereira, B. Nagender Nath, S.D. Iyer, D.V. Borole, G. Parthiban, R. Jijin, V. Khedekar

Date: 2016-04-15

shards (no of shards g−1 of sediment) in BC 14, 20 and 25 with respect t...sediment cores. ...cores. The abundance of glass shards, composition of bulk sediments, and...sediment cores. The data of core BC 8 are provided for comparison. ...sediment cores from the CIB. ...sediment cores collected from water depths >5000m along the transect 76...sediment. The cryptotephra forms the fifth ash horizon and is of ~34ka...cores yielded five volcanic horizons of which four have visual and dispersed...late Quaternary sediments from the Central Indian Basin...bulk sediments). ... CIB sediment cores. ...sub-samples from the three sediment cores. The data of core BC 8 are provided...recovered from three sediment cores from the CIB. ...sediment) in BC 14, 20 and 25 with respect to age (ka) of the cores, with...cores BC 14, BC 20 and BC 25 showing sedimentation rates of 0.27, 0.23...sediments were used to distinguish the volcanic horizons. Of the four ... We have investigated three sediment cores collected from water depths >5000m along the transect 76°30′E in close proximity to a fracture zone in the Central Indian Basin (CIB). The cores yielded five volcanic horizons of which four have visual and dispersed shards. Rhyolitic glass shards of bubble wall, platy, angular and blocky types were retrieved from various stratigraphic horizons in the cores. The abundance of glass shards, composition of bulk sediments, and 230Thexcess ages of the host sediments were used to distinguish the volcanic horizons. Of the four volcanic horizons, three are now newly reported and correspond to ages of ~85, 107–109 and 142–146ka while the fourth horizon is of 70–75ka. By using trace element ratios and Cr and Nb-based normative calculations, cryptotephra has been identified for the first time from the CIB sediment. The cryptotephra forms the fifth ash horizon and is of ~34ka.

Contributors: N. Basavaiah, J.L.V. Mahesh Babu, P.B. Gawali, K.Ch.V. Naga Kumar, G. Demudu, Siddharth P. Prizomwala, P.T. Hanamgond, K. Nageswara Rao

Date: 2015-06-12

cores were obtained which included significant peat. The conventional ...layers of the cores as indicated by SIRM/χ values (Fig. 4). For example...inter-deltaic sediments at Kolleru Lake (after Biswas, 1993; Rode et al...sediments. The variation in magnetic mineralogy is related to paleoclimatic...Down-core and Late Quaternary temporal variations in environmental magnetic...sediments at Kolleru Lake (after Biswas, 1993; Rode et al., 2010; Nageswara...during the Late Quaternary period with their mineral magnetic and geochemical...cores, the details of which are given in Table 1, were collected from ...during the Late Carboniferous, resulting in deposition and preservation...cores RG, MW, PN and PP. (b) Age depth model for RG, MW and PN sediment...cores corroborated by mineral magnetic and geochemical proxies indicates...sections of cores RG, MW, PN and PP. (b) Age depth model for RG, MW and...Down-core and Late Quaternary temporal variations in elemental concentrations... of the cores as indicated by SIRM/χ values (Fig. 4). For example, the...cores are characterized by such transition from magnetite to hematite ...sediments representing the inter-deltaic part of the Krishna–Godavari ...Down-core and Late Quaternary temporal variations in environmental magnetic...Late Carboniferous, resulting in deposition and preservation of an ∼8 ...Late Quaternary environmental and sea level changes from Kolleru Lake,...traps of Late Cretaceous–Palaeocene age, Archaean granites and unclassified...Down-core and Late Quaternary temporal variations in elemental concentrations...Late Quaternary period with their mineral magnetic and geochemical imprints...cores as indicated by SIRM/χ values (Fig. 4). For example, the peat sediments...Late Pleistocene. Similarly, the peat layers rich in mangrove pollen indicate...Late Cretaceous–Palaeocene age, Archaean granites and unclassified crystallines...cores as indicated by SIRM/χ (Saturation Isothermal Remanent Magnetization...sediment record compared to climatically modulated riverine supply. The ... The present study employs mineral magnetic, geochemical, and textural parameters to elucidate the climate and sea level change signatures from Kolleru lake sediments representing the inter-deltaic part of the Krishna–Godavari sedimentary basin (KG basin). For this purpose, four cores were obtained which included significant peat. The conventional radiocarbon dating suggested that the peat formation took place during 9 ka–6 ka with an average sedimentation rate of 0.31 cm/y. Thermomagnetic analysis identifies titanomagnetite, magnetite and hematite as the dominant magnetic mineralogy of the KG basin sediments. The variation in magnetic mineralogy is related to paleoclimatic and paleoenvironmental processes; the transitions between (titano)magnetite and hematite coincide with peat layers of the cores as indicated by SIRM/χ (Saturation Isothermal Remanent Magnetization/Magnetic Susceptibility) and S-ratio defined by IRM−0.3T/SIRM values. The various mineral magnetic parameters, χ and S-ratio along with major elemental concentrations of Ti, Al, Fe and Zr show signatures of an arid event before 10 ka, between 9 ka–8 ka periods and during the last 5.5 ka. The overall climate of warm and humid type was inferred from 10 ka to 9 ka, which correlates with Early Holocene Optima and 6 ka to 5.5 ka of Middle Holocene. The presence of evaporite crystals in the lowermost part of the cores corroborated by mineral magnetic and geochemical proxies indicates sub-aerially weathered facies of the arid Late Pleistocene. Similarly, the peat layers rich in mangrove pollen indicate sea level changes between 10 ka and 6 ka. The sub-surface position of the Pleistocene weathered layer and the Holocene peat layer suggests tectonic subsidence of the area, which is situated over the basement graben, known as Gudiwada sub-basin.

Contributors: Olaf Juschus, Maksim Pavlov, Georg Schwamborn, Frank Preusser, Grigory Fedorov, Martin Melles

Date: 2011-11-01

Quaternary lake-level history as derived from sediment cores from the ...sediment cores at the southern shelf and in the deepest part of the lake...sediments on the shelf indicate high lake levels during a warm Mid-Pleistocene...cores Lz1027 and Lz1028 from the southern lake shelf. The oldest sediments...Late Quaternary...sediment cores from the southern lake shelf. There, a cliff-like bench...Late Quaternary...late glacial times the lake level was around 10m lower than today (d).... In late glacial times the lake level was around 10m lower than today ...and position of sediment cores at the southern shelf and in the deepest...relation to wet sediment weight. ...Late Quaternary lake-level changes of Lake El'gygytgyn, NE Siberia...sediment weight. ... to dry sediment weight. ...sediment parallel to the coast and towards the outlet, where the material...from cores Lz1027 and Lz1028 from the southern lake shelf. The oldest sedim...sedimentation occurred. Subsequently, the lake level rose rapidly to the ... Lake El'gygytgyn is situated in a 3.6Ma old impact crater in northeastern Siberia. Presented here is a reconstruction of the Quaternary lake-level history as derived from sediment cores from the southern lake shelf. There, a cliff-like bench 10m below the modern water level has been investigated. Deep-water sediments on the shelf indicate high lake levels during a warm Mid-Pleistocene period. One period with low lake level prior to Marine Oxygen Isotope Stage (MIS) 3 has been identified, followed by a period of high lake level (10m above present). In the course of MIS 2 the lake level dropped to −10m. At the end of MIS 2 the bench was formed and coarse beach sedimentation occurred. Subsequently, the lake level rose rapidly to the Holocene level. Changes in water level are likely linked to climate variability. During relatively temperate periods the lake becomes free of ice in summer. Strong wave actions transport sediment parallel to the coast and towards the outlet, where the material tends to accumulate, resulting in lake level rise. During cold periods the perennial lake ice cover hampers any wave activity and pebble-transport, keeping the outlet open and causing the lake level to drop.

Contributors: Selin Eda TEKIROĞLU, Vedat EDIGER, Semal YEMENICIOĞLU, Selim KAPUR, Erhan AKÇA

Date: 2001-01-01

the cores. ...content (%) of the sediments; unit 1 (+), unit 2 (x), unit 3 (▵) turbidites... silt content (%) of the sediments; unit1 (+), unit2 (x), unit 3 (▵) turbidites...sediments; unit 1 (+), unit 2 (x), unit 3 (▵) turbidites and coccoliths...core, off the south-eastern shelf, indicates the downward increasing precipitation...sediments, some with organic material. The metal concentration is diluted...sedimentation pattern and sedimented material is believed to be the response...core. ...cores. ... taken from each core. ...sediments of Black Sea. ...types of rocks and sediments of Black Sea. ...Late Quaternary deposits of the Black Sea...sediments; unit1 (+), unit2 (x), unit 3 (▵) turbidites and coccoliths ...sediments taken from the south-eastern and western Black Sea have been...sediments form the shore deposits, the deep-sea sediments mainly consist ... Holocene sediments taken from the south-eastern and western Black Sea have been investigated in relation to their geochemical, sedimentological and mineralogical characteristics. Their textures are characterized by their low amount of sand, upward-increasing silt and downward-increasing clay contents. While the terrigenous materials transported from Anatolian volcanic-based sources and European alluvial sediments form the shore deposits, the deep-sea sediments mainly consist of the marine biological production. The highest amount of organic carbon was deposited following the formation of anoxic conditions at the bottom until the beginning of the still continuing carbonate-rich coccolith (Emiliania huxleyi) deposition. The high metal concentrations are associated with fine-grained sediments, some with organic material. The metal concentration is diluted by high organic carbon and carbonate contents within the depositional sequences. While the abundance of illite in the western Black Sea describes the deltaic depositions, the downward decreasing smectite/illite ratio along the core, off the south-eastern shelf, indicates the downward increasing precipitation during the deposition. The variation in the sedimentation pattern and sedimented material is believed to be the response of the biochemical environment in the sea to the changing geological, biological and chemical conditions in and around the Black Sea during the last climatic changes.

Contributors: Wells, Patricia, Wells, Graeme, Cali, Joe, Chivas, Allan R

Date: 1994-02-18

Core...Late Quaternary sediments of core BMR96GC21 in the southeast Indian Ocean ... Abstract: Not Available Category: geoscientificInformation Source: Not Available Supplemental Information: Not Availble Coverage: EVENT LABEL: * LATITUDE: -23.772167 * LONGITUDE: 108.500667 * ELEVATION: -2100.0 m * Recovery: 1.8 m * LOCATION: Southeast Indian Ocean * DEVICE: Core

Contributors: Bernhard Diekmann, Gerhard Kuhn, Volker Rachold, Andrea Abelmann, Uta Brathauer, Dieter K Fütterer, Rainer Gersonde, Hannes Grobe

Date: 2000-01-01

sediment. We discuss downcore variations of compositional data of two sediment cores from the northern and southern Scotia Sea that correlate...stages in the investigated sediment cores and reference core RC11-120 ...Late Quaternary marine sediments from the Scotia Sea trace sources and...Late Quaternary marine sediments from the Scotia Sea trace sources and...parameters in sediment core PS2515-3 from the northern Scotia Sea: Gr,...sediment provenance...Sediments were derived from very different sources at both localities,...sediment transfer from adjacent seas. The observed temporal compositional...sediment cores and reference core RC11-120 (Hays et al., 1976). Stratigraphic...sediment cores PS2319-1 (○) and PS2515-3 (•). Sediment core samples comprise...pre-Quaternary sediments, and coastal erosion along the eastern Patagonian...from sediment cores PS2319-1 (○) and PS2515-3 (•). Sediment core samples...the SPECMAP ages presented for the sediment-core data. Especially the ...sediment input of interbasinal origin. Current transport is mainly responsible... and in samples from sediment cores PS2319-1 (○) and PS2515-3 (•). Sediment...pre-Quaternary sediments scoured on the Burwood Bank. The small inset ...sediment supply in the Scotia Sea (Southern Ocean): response to Late Quaternary ... Geochemical and mineralogical compositions of modern and Late Quaternary marine sediments from the Scotia Sea trace sources and transport paths of terrigenous sediment. We discuss downcore variations of compositional data of two sediment cores from the northern and southern Scotia Sea that correlate with fluctuations in magnetic susceptibility. Sediments were derived from very different sources at both localities, as revealed by contrasting clay-mineral assemblages. However, a common feature is the input of more basic and undifferentiated crustal material with the potential of high magnetic susceptibility during glacial periods, indicated by variable quartz/feldspar ratios and major, trace and rare earth elements. Terrigenous sediments mainly originate from nearby terrestrial sources or are introduced through interbasinal sediment transfer from adjacent seas. The observed temporal compositional variations have to be attributed to changes in the relative detrital contributions from the diverse source areas. Ice-mass extensions in southern Patagonia, on the Antarctic Peninsula and adjacent islands likely control the supply of glaciogenic detritus to the open ocean during times of glacial expansion, diluting the sediment input of interbasinal origin. Current transport is mainly responsible for sediment dispersal to the pelagic Scotia Sea and may amplify the glaciological source signals during glacial climate periods, because of a stronger wind forcing of the Antarctic Circumpolar Current.

Contributors: M Thamban, V Purnachandra Rao, R.R Schneider

Date: 2002-07-10

sediment cores from the western margin of India...in core GC-5. Intervals showing enhanced gibbsite peaks are shown by +... ...Do...ratios in core GC-3. Presence of gibbsite is marked by + signs. Age scale...Down-core variations in grain size parameters, major clay mineral percentages...core GC-3. Presence of gibbsite is marked by + signs. Age scale is based...late quaternary...Down-core variations in grain size parameters, major clay mineral percentages...cores. C – chlorite, G – gibbsite, I – illite, K+C – kaolinite+chlorite...late Holocene witnessed reduced rainfall activity and resultant decrease...late Quaternary monsoon oscillations based on clay mineral proxies using...core GC-5. Intervals showing enhanced gibbsite peaks are shown by + marks...late Quaternary, two sediment cores from the southwestern continental ...core off Cochin. Illite with increasing kaolinite content towards the core top was found to dominate in a core from the continental slope off...late quaternary...late glaciation, with distinct events of intensification at ∼28 000 and...cores and schematic geological map of the study area. Core GC-3 is from...late Quaternary, two sediment cores from the southwestern continental ... In order to reconstruct the variations in the intensity of summer monsoon precipitation during the late Quaternary, two sediment cores from the southwestern continental margin of India were studied for their clay mineral composition and grain size parameters. Kaolinite, illite and gibbsite were dominant in a core off Cochin. Illite with increasing kaolinite content towards the core top was found to dominate in a core from the continental slope off Goa. Major sources of clays at both the core sites were from the hinterland rocks and soils. Careful evaluations of several factors that could complicate the clay distribution in marine environment indicate that the clay mineral parameters can be used as proxies for the intensity of summer monsoon precipitation in the past. The relatively low values of humidity proxies (kaolinite content, K/C and K/I ratios) and higher illite crystallinity with significant variations indicate that the summer monsoons in general were weaker during the late glaciation, with distinct events of intensification at ∼28 000 and 22 000 yr BP. The last deglaciation was characterised by an increased terrigenous input with high values of humidity proxies during 15 700–14 800 cal yr BP, indicating an early strengthening of summer monsoon activity in the region. The most remarkable increase in kaolinite content, K/C and K/I ratios associated with much reduced values of chlorite and illite and illite crystallinity, however, occur between 8800 and 6400 cal yr BP. It appears that the Holocene precipitation maxima occurred after 9000 cal yr BP and lagged behind the precessional forcing. The late Holocene witnessed reduced rainfall activity and resultant decrease in hydrolysis starting at 5600 cal yr BP.