Uppermost Pleistocene Research Articles

Insect trace fossils as indicators of climatic conditions during the uppermost Pleistocene deposits in southern Brazilian Atlantic coast

AbstractThe Rio Grande do Sul Coastal Plain records sea-level oscillations driven by climatic changes during Quaternary glaciations, represented as four lagoon-barrier systems, the last one forming after the last glacial maximum and still active. Marine trace fossils are reported in the Pleistocene deposits, but terrestrial burrows also occur in the eolian deposits. The insect trace fossil assemblages from the uppermost Pleistocene deposits of the lagoon-barrier system III are used as relative proxies to infer the climate regimes that controlled sedimentation prior to the last glacial maximum. Two suites occur in the eolian deposits: the Vondrichnus suite, dominated by structures produced by termites, in the basal eolian beds; and the Celliforma suite, dominated by hymenopteran (bees and wasps) structures, in the upper eolian beds. The dominance of termite nests indicates humid conditions. The shift upward to the Celliforma suite signals a change in the humidity regime and the prevalence of drier conditions. The stratigraphic position of the ichnoassemblage, above the uppermost Pleistocene marine transgressive beds that formed during the last interglacial and below the record of the last glacial maximum in this coastal plain, suggests that the last glacial interval controlled this humid-dry fluctuation.

The uppermost Pleistocene–Holocene mud drape across the Marmara Sea: Quantification of detrital supply from southern Marmara rivers

The Marmara Sea (area 11,350 km2; volume 3378 km3; central basins >1100 m deep) straddles the North Anatolian Transform Fault separating the Eurasian and Aegean-Anatolian tectonic plates. Along with the shallow straits of Dardanelles and Bosphorus (depths ~63 m and ~40 m, respectively), the Marmara Sea forms the only marine connection between the Black Sea and the eastern Mediterranean. During Pleistocene glacial stages, the modern straits were subaerial valleys and the modern Marmara basin was occupied by the landlocked Propontis Lake. Previous researchers attributed major portions of a widely distributed uppermost Pleistocene–Holocene mud blanket (locally >10–25 m thick; volume 43–47 km3) to transport of suspended load through one or both of the straits, as either the Aegean Sea (at ~13.8 cal ka) or the Neoeuxine Lake (today's Black Sea, at ~11.1 cal ka) began to spill into the Marmara basin. To test these suggestions, the thicknesses and volume of the mud blanket were determined from >5000 line-km of airgun, sparker and boomer profiles and > 100 cores, and compared with the contemporary supply from local rivers to decide, by difference, if the straits might have had a significant role. Volume calculations for the detrital supply from rivers rely on (1) decades of daily water- and sediment-discharge data from gauging stations, acquired before 20th century dam construction and, independently, (2) the BQART model which uses a variety of hydrological, geomorphic, geological and climate data. These calculations demonstrate that >85–90% of the detritus in the offshore mud blanket was supplied by steep rivers (Kocasu River and its tributaries) and mountainous streams draining the highlands of the southern Marmara region. Geochemistry of the <38 μm fraction supports this source. Any input through the Dardanelles has been sporadic and limited to perhaps ~5 Gt of suspended load (equivalent to ~5.2 km3 of porous mud when deposited) because of changing directions and rates of flow since the Last Glacial Maximum. Resedimentation through mass wasting and transgressive shoreface erosion appear to be minor compared with river supply. The isolated nature of the Marmara basin and its supply from mostly a single watershed afford an opportunity to verify the reliability of this type of hindcast analysis, based upon sediment-discharge data and catchment models – analysis which cannot be completed with a comparable level of certainty along open marine coastlines elsewhere.

Stratigraphy and origin of the uppermost Pleistocene to Holocene succession exposed on the Shinjima (Moeshima) Island, inner Kagoshima Bay, SW Japan

新島に露出する姶良カルデラ底下の最上部更新統〜完新統堆積物について，これまで議論のあった岩相層序を見直し，下位から順に下部新島シルト層，新島軽石，新島南部軽石，上部新島シルト層，燃島貝層に区分した．堆積物の産状や貝類，珪藻，有孔虫，貝形虫などの化石に基づけば，上部・下部新島シルト層は水深100-200mの内湾静水域の堆積物で，桜島などに由来するテフラを挟む．燃島貝層は桜島起源のラハール堆積物で，新島軽石と新島南部軽石は13-12kaの短期間に噴出した若尊カルデラ起源の水底密度流堆積物と考えられる．既知のテフラとの対比と14C年代などによれば，これらが堆積した時期は13 cal ka BPから2cal ka BPまでといえる．

The first directly dated evidence for Palaeolithic occupation on the Indian coast at Sandhav, Kachchh

South Asia has a rich Palaeolithic heritage, and chronological resolution for this record has substantially improved over the past decade as a result of focused, interdisciplinary research at a number of key sites. Expanding the spatial diversity of dated Palaeolithic sites in South Asia grows increasingly important to examine how patterns of change through time vary within and between the region’s diverse habitats. Critically, alternate models of modern human dispersals into South Asia highlight the significance of either coastal or continental routes of dispersal, but currently no coastal Palaeolithic sites directly dating to the timeframe of human expansions are known. Our previous research in Kachchh was the first study to clearly identify the presence of Palaeolithic sites in Late Pleistocene landscapes in close proximity to the Indian Ocean coastline. Here, we present the first results of surface survey and test excavation at the site of Sandhav (Kachchh, India), approximately 25 km from the modern shoreline. We characterise the geomorphology of the landscape, highlighting multiple phases of alluvial aggradation and post-depositional carbonate formation, associated with Palaeolithic artefacts. To date, excavations have tested the uppermost Pleistocene deposit, yielding a small collection of fresh Middle Palaeolithic artefacts associated with a luminescence age dating to the first half of MIS 5 (∼114 ka), which provides a minimum age for Late Acheulean artefacts in underlying units. We discuss our findings in the context of debates surrounding the timing, lithic technologies, and ecologies associated with the expansions of modern humans into South Asia.

KVARTÉRNÍ SEDIMENTY NA SEVERNÍM PŘEDHRADÍ LOKALITY POHANSKO U BŘECLAVI

Sedimentological study on the Northern bailey of the fortified site Pohansko allows identification of 9th lithofacies and 2 facies associations. The lower facies association is interpreted as an infill of fluvial channels (mostly mid-channel dunes) with two cycles of filling. The fluvial channels were relatively shallow and broad (high width/depth channel ratio) and they point to braided fluvial style and channel migration. The upper fluvial association reflects significant change of the fluvial style. The sedimentary infill of the upper fluvial association is interpreted as deposits of levee and overbank deposits. Results of the OSL dating for the sample of lower facies association provide an age of 13.5 ky. Such age can be correlated with the Upper Pleistocene Allerød Interstadial (13.7‒12.9 ky BP), i.e. relatively warmer phase of the Weichselian late glacial. Data of OSL dating for two samples from the upper facies association were 11.8 ky and 10.3 ky BP. The upper age can be correlated with Younger Dryas (12.9‒11.7 ky BP) whereas the lower one to Preboreal. The deposition of the upper facies associations are therefore interpreted as Uppermost Pleistocene to Early Holocene in age.

Diatom analysis of the uppermost Pleistocene to Holocene drilled core at Sarufutsu, northern Hokkaido, Japan:

Diatom analysis of the uppermost Pleistocene to Holocene drilled core at Sarufutsu, northern Hokkaido, Japan:

北海道東部厚岸湾・湖底表層堆積物と厚岸湾沖積層コアの珪藻分析 : 堆積環境・塩分指数・電気伝導度の検討

北海道東部厚岸湾・湖底表層堆積物と厚岸湾沖積層コアの珪藻分析 : 堆積環境・塩分指数・電気伝導度の検討

Late Pleistocene–Holocene palaeoenvironmental evolution of the Añamaza River valley (Iberian Range, NE Spain): Multidisciplinary approach on the study of carbonate fluvial systems

Abstract The uppermost Pleistocene and Holocene palaeoenvironmental evolution of the Anamaza river valley (Iberian Range, NE Spain) is deduced using multidisciplinary approach including stratigraphical, mineralogical, palynological, geochemical, geophysical methods and drilling. Main changes were registered in distinct subenvironments of a carbonate fluvial system, including the channelled zone and wetlands in the floodplain. Tufa barrages dominated although pools also existed. Geophysical survey and coring reveal tufa build-ups and pool facies also in the subsoil. Lower water temperature and scarce evaporation are deduced for the Pleistocene fluvial system that progressively changed through the Holocene, with more hydrologically closed areas and higher evaporation influence. A general aggrading evolution during warm stages related with increasing base level and damming due to fast carbonate precipitation, characterised the Holocene. Detrital tufa indicates erosive high-energy floods or colder stages when water level would decrease favouring erosion. 14 C and 230 Th/ 234 U dating reveal high sedimentation rates and three main discontinuities related with cold episodes: Younger Dryas, middle part of the Holocene Climate Optimum and Iron Age Epoch. During the uppermost Pleistocene tufa growth would be enhanced during warmer episodes as the Bolling/Allerod. In the Younger Dryas scarce vegetation favoured erosion of both, slopes and tufa constructions. Subsequent warmer temperatures during the first part of the Holocene favoured vegetated slopes, enhanced tufa growing (although interrupted in the middle part of the Holocene Climate Optimum), and development of wetlands with riparian vegetation in the floodplain, where either siliciclastics or detrital tufa incoming alternated with low-energy waters stages and mud settling. Progressive decline in tufa is deduced for the upper Holocene but it is not possible to determine whether this, and other palaeoenvironmental changes were related either to climate or increasing human activities. During the Roman and Medieval Warm Periods more oxidizing conditions in the wetlands and increasing erosion prevailed, probably conditioned by human activities. The pollen record shows for the Early Holocene development of Pinus forest with Betula, and expansion of deciduous Quercus, xerophilous and heliophilous grassland. Subsequent increasing moisture supported open forests with deciduous (Quercus, Ulmus, Corylus) and evergreen (Quercus ilex, Pistacia) species. From ca.4000 yrBP, a dominant deciduous Quercus forest with groves of Corylus, Ulmus, Acer, Fagus and Taxus expanded and human activities (grazing) occurred. From 1200 yrBP dry grassland expanded due to intensive land use (agropastoral activities). Almost completely deforested plateaus surround the site today with slopes covered by patchy grass with junipers groves and screeds with little soil.

Geo-archaeology of the Roman palaeosurface of Sena Gallica (Senigallia, Italy)

ABSTRACTSena Gallica (Senigallia), in the northern Marche region, was the first Roman colony on the Adriatic coast founded at the beginning of the third century BC. This research adopted an integrated approach to different information sources that combines old and new data, archaeological excavations, topographic and geophysical surveys, and geological and geomorphological analyses. The data are managed within a GIS and supported by 3D modelling. One of the results of this work is a map which represents the geomorphological setting of the Roman colony, close to the mouth of the Misa river. The settlement exploited the top-surface of the uppermost Pleistocene–early Holocene coastal fan of the Misa river, now only preserved at the apex sector truncated seaward by wave erosion. The top-surface of the fan apex, in turn, was partly re-incised by stream erosion producing a series of slight topographic mounds, which were selected for the earliest human settlement (V-IV c. BC). Some of the mounds resulted in a protected, slightly elevated, area enclosed by the meandering course of the Misa River and the Sant'Angelo/Penna streams, where the Romans decided to found their colony (284 BC). The tight interaction between human activities and the natural environment has always influenced the development of the town, from the earliest phases to the modern age. This map focuses on the time when the Roman colony was founded, but the combined study in progress allows understanding of the main transformations that occurred during the following centuries.

Late Quaternary aggradation rates and stratigraphic architecture of the southern Po Plain, Italy

AbstractThePoRiverBasin, where accumulation and preservation of thick sedimentary packages are enhanced by high rates of tectonic subsidence, represents an ideal site to assess the relations between vertical changes in stratigraphic architecture and sediment accumulation rates. Based on a large stratigraphic database, a markedly contrasting stratigraphy ofLatePleistocene andHolocene deposits is reconstructed from the subsurface of the modern alluvial and coastal plains. Laterally extensive fluvial channel bodies and related pedogenically modified muds of latest Pleistocene age are unconformably overlain byHolocene overbank fines, grading seaward into paralic and nearshore facies associations. In the interfluvial areas, a stiff paleosol, dating at about 12.5–10 cal kyBP, marks thePleistocene–Holocene boundary. Across this paleosol, aggradation rates (ARs) from 16 radiocarbon‐dated cores invariably show a sharp increase, from 0.1–0.9 mm year−1to 0.9–2.9 mm year−1. Comparatively lowerPleistocene values are inferred to reflect fluvial activity under a low‐accommodation (lowstand and early transgressive) regime, whereas higherARs during theHolocene are related to increasing accommodation under late transgressive and highstand conditions. Holocene sediment accumulation patterns vary significantly from site to site, and do not exhibit common trends. Very high accumulation rates (20–60 mm year−1) are indicated by fluvial channel or progradational delta facies, suggesting that extremely variable spatial distribution ofHoloceneARs was primarily controlled by autogenic processes, such as fluvial channel avulsion or delta lobe switching. ContrastingARbetween uppermostPleistocene andHolocene deposits also are reported from the interfluves of several coeval, alluvial‐coastal plain systems worldwide, suggesting a key control by allogenic processes. Sediment accumulation curves from adjacent incised valley fills show, instead, variable shapes as a function of the complex mechanisms of valley formation and filling.

Correlation between electrical conductivity and salinity index calculated from diatom assemblages of the uppermost Pleistocene to Holocene cores drilled in the Ishikari lowland, Hokkaido, Japan

Correlation between electrical conductivity and salinity index calculated from diatom assemblages of the uppermost Pleistocene to Holocene cores drilled in the Ishikari lowland, Hokkaido, Japan

Geologic framework of the northern North Carolina, USA inner continental shelf and its influence on coastal evolution

The inner continental shelf off the northern Outer Banks of North Carolina was mapped using sidescan sonar, interferometric swath bathymetry, and high-resolution chirp and boomer subbottom profiling systems. We use this information to describe the shallow stratigraphy, reinterpret formation mechanisms of some shoal features, evaluate local relative sea-levels during the Late Pleistocene, and provide new constraints, via recent bedform evolution, on regional sediment transport patterns. The study area is approximately 290 km long by 11 km wide, extending from False Cape, Virginia to Cape Lookout, North Carolina, in water depths ranging from 6 to 34 m. Late Pleistocene sedimentary units comprise the shallow geologic framework of this region and determine both the morphology of the inner shelf and the distribution of sediment sources and sinks. We identify Pleistocene sedimentary units beneath Diamond Shoals that may have provided a geologic template for the location of modern Cape Hatteras and earlier paleo-capes during the Late Pleistocene. These units indicate shallow marine deposition 15–25 m below present sea-level. The uppermost Pleistocene unit may have been deposited as recently as Marine Isotope Stage 3, although some apparent ages for this timing may be suspect. Paleofluvial valleys incised during the Last Glacial Maximum traverse the inner shelf throughout the study area and dissect the Late Pleistocene units. Sediments deposited in the valleys record the Holocene transgression and provide insight into the evolutionary history of the barrier-estuary system in this region. The relationship between these valleys and adjacent shoal complexes suggests that the paleo-Roanoke River did not form the Albemarle Shelf Valley complex as previously proposed; a major fluvial system is absent and thus makes the formation of this feature enigmatic. Major shoal features in the study area show mobility at decadal to centennial timescales, including nearly a kilometer of shoal migration over the past 134 yr. Sorted bedforms occupy ~ 1000 km 2 of seafloor in Raleigh Bay, and indicate regional sediment transport patterns between Capes Hatteras and Lookout that help explain long-term sediment accumulation and morphologic development. Portions of the inner continental shelf with relatively high sediment abundance are characterized by shoals and shoreface-attached ridges, and where sediment is less abundant, the seafloor is dominated by sorted bedforms. These relationships are also observed in other passive margin settings, suggesting a continuum of shelf morphology that may have broad application for interpreting inner shelf sedimentation patterns. • We mapped ~ 3200 km 3 of the North Carolina inner continental shelf. • Modern Cape Hatteras may have been the location of several ancient paleo-capes. • Major shoal complexes are shown to migrate ~ 1 km per century. • Sediment availability determines the morphology of the inner continental shelf. • Seafloor bedforms reflect sediment availability and transport directions.

New evidence for large earthquakes on the Central Iran plateau: palaeoseismology of the Anar fault

SUMMARY The Central Iran plateau appears aseismic during the last few millenniums based on instrumental and historical seismic records. Nevertheless, it is sliced by several strike-slip faults that are hundreds of kilometres long. These faults display along-strike, horizontal offsets of intermittent gullies that suggest the occurrence of earthquakes in the Holocene. Establishing this is crucial for accurately assessing the regional seismic hazard. The first palaeoseismic study performed on the 200-km long, NS striking Anar fault shows that this right-lateral fault hosted three large (Mw≈ 7) earthquakes during the Holocene or possibly Uppermost Pleistocene for the older one. These three seismic events are recorded within a sedimentary succession, which is not older than 15 ka, suggesting an average recurrence of at most 5 ka. The six optically stimulated luminescence ages available provide additional constraints and allow estimating that the three earthquakes have occurred within the following time intervals: 4.4 ± 0.8, 6.8 ± 1 and 9.8 ± 2 ka. The preferred age of the more recent event, ranging between 3600 and 5200 yr, suggests that the fault is approaching the end of its seismic cycle and the city of Anar could be under the threat of a destructive earthquake in the near future. In addition, our results confirm a previous minimum slip rate estimate of 0.8 ± 0.1 mm yr−1 for the Anar fault indicating that the westernmost prominent right-lateral faults of the Central Iran plateau are characterized by slip rates close to 1 mm yr−1. These faults, which have repeatedly produced destructive earthquakes with large magnitudes and long recurrence interval of several thousands of years during the Holocene, show that the Central Iran plateau does not behave totally as a rigid block and that its moderate internal deformation is nonetheless responsible for a significant seismic hazard.

Coastal barrier dune construction during sea-level highstands in MIS 3 and 5a on Tottori coast-line, Japan

The southern coast of Japan Sea exhibits a number of Late Pleistocene coastal barrier dunes, where the sediment record potentially provides important evidence for the palaeoenvironmental history of East Asia. The lack of direct dating of these barrier dunes, however, has veiled relationships between dune deposition, sea level, and other controlling factors. Quartz single aliquot regenerative optically-stimulated luminescence (OSL) dating was applied to the Late Pleistocene barrier dune at the Tottori coast, southern central Japan Sea. We investigated a borehole drilled in a continuous ground-penetrating radar (GPR) profile of the dune and an outcrop excavation, where there has been recognised a sedimentary succession exposed of the Pleistocene dune sand, palaeosol, Daisen–Kurayoshi Pumice (DKP) tephra, palaeosol, and Holocene dune sand, in ascending order. The gradual transition from the Pleistocene dune sand to palaeosol indicates a termination of the Late Pleistocene dune activity. Five OSL ages from the uppermost Pleistocene dune overlap within the period 48.2–51.4 ka, which confirms that both deposition and termination of the dune occurred in early to mid Marine Isotope Stage (MIS) 3. Another OSL age from the lower section was 77.7 ± 6.1 ka, and indicates an earlier depositional stage in late MIS 5a. These reveal that the coastal dune deposition occurred in relation to the sea-level highstands. It would appear that a sea level of c. –50 m relative to the present was the threshold for the dune activation. Morphology and sediment distribution of the modern shelf off the Tottori coast suggest that the sea-level lower than − 50 m leads to increasingly unfavourable conditions for coastal dune activity due to longer sediment transport distances and decreased sediment supply. These results have implications for the Late Pleistocene barrier dune along the southern Japan Sea coast and suggest that other dunes, correlated with Tottori based on the DKP tephra, possibly would also have experienced a similar termination in relation to the sea-level fall from mid MIS 3. Results also demonstrate that the depositional setting of the Late Pleistocene dunes was different from those constructed in the Holocene due to the lower interstadial sea-level highstands and resultant longer distance to the shore during MIS 3 and 5a. As a result, the Pleistocene dune exhibits less pronounced stratification and in finer grain size than the outer Holocene dune ridge, where sand is directly fed from the shore. The grain size of the inner Holocene dune ridge in contrast is almost identical to the Pleistocene dune, suggesting that the inner ridge partly consists of sand reworked from the Pleistocene dune.

Heavy mineral stratigraphy of sediments from the southern outer shelf of the East China Sea since the last glaciation using fuzzy C-means cluster method

Correspondence analysis and fuzzy C-means cluster methods were used to divide the stratigraphy of heavy mineral assemblages, and the sediment sources and depositional dynamics of the environment reconstructed. The assemblages were taken from marine sediments from the late Pleistocene to the Holocene in Core Q43 situated on the outer shelf of the East China Sea. Based on the variable boundaries of the mineral assemblage at 63 and 228 cmbsf (cm below sea floor), the core might have previously been divided into three sediment strata marked with units I, II and III, which would be consistent with the divided sediment stratum of the core using minor element geochemistry. The downcore distribution of heavy minerals divided the sedimentary sequence into three major units, which were further subdivided into four subunits. The interval between 0 and 63 cmbsf of the core (unit I), which spans the Holocene and the uppermost late Pleistocene, is characterized by a hornblende-epidote-pyroxene assemblage, and contains relatively a smaller amount of schistic mineral and authigenic pyrite. In comparison, the interval between 63 and 228 cmbsf (unit II), is representative of the Last Glacial Maximum (LGM), and features a hornblende-epidote-magnetite-ilmenite assemblage containing the highest concentrations of heavy minerals and opaque minerals. However, the interval between 228 and 309 cmbsf (unit III), which spans the subinterglacial period, is characterized by a hornblende-authigenic-pyrite-mica assemblage. Relative ratios of some heavy minerals can be used as tracers of clastic sediment sources. The lower part of the sediment core shows the highest magnetite/ilmenite ratio and relatively high hornblende/augite and hornblende/epidote ratios. The middle core shows the highest hornblende/augite and hornblende/epidote ratios, and the lowest magnetite/ilmenite ratio. The upper part exhibits a slightly higher magnetite/ilmenite ratio, and also the lowest hornblende/augite and hornblende/epidote ratios. The distribution of the mineral ratio is consistent with stratigraphic division in heavy mineral data using correspondence analysis and fuzzy C-means clustering. Variations in heavy mineral association and mineral ratio in core Q43 revealed changes in provenance and depositional environment of the southern outer shelf of the East China Sea since the late Pleistocene, well corresponding to interglacial and glacial cycles.

Shallow Subsurface Geology of the Ohmi Basin

This study clarified the stratigraphy and sedimentary facies of the shallow subsurface strata of the Ohmi Basin, an inland lake basin in central Japan. Stratigraphic divisions in the basin are based on regional tephra and widely distributed humic layers. The shallow subsurface strata of the basin are divided into two units. Unit II comprises middle to upper Pleistocene terrace deposits. The overlying Unit I comprises uppermost Pleistocene to Holocene postglacial deposits. Although the lithofacies of Unit II vary horizontally and vertically, the uppermost part consistently consists of humic soils containing Aira-Tn tephra (AT). This distinctive tephra is widely distributed throughout the Japanese islands. Humic soils were deposited at ca. 16.5 to 25 ka according to 14C dating. Unit I, which conformably overlies Unit II, and is mainly a repetitive succession of sand, mud, and gravel. Each layer is discontinuous in terrestrial areas, where distribution patterns of lithofacies are controlled by topography. The depth distribution of AT reflects tectonic subsidence induced by reverse faulting in the Biwako-Seigan active fault zone on the western side of Lake Biwa. Thus, tectonic movement was an important factor during sedimentation. Periodic small-scale subsidence (less than several meters per event) due to slips along faults of the Biwako-Seigan system caused discontinuities in late Quaternary fluvial deposits.

Facies and ground‐penetrating radar characteristics of coarse‐grained beach deposits of the uppermost Pleistocene glacial Lake Algonquin, Ontario, Canada

AbstractThe lithofacies of the uppermost Pleistocene (ca 11 800 to 10 400 14C yr bp), cold‐temperate, coarse‐grained beach deposits of Lake Algonquin, the precursor of the present Lake Huron of North America, have been studied and interpreted based on analogous features of modern beaches from the same region. Ice foot and ice‐cementation develop during winter but, unlike Arctic beaches, ice‐related sedimentary features are seldom, if ever, preserved in the Pleistocene and recent deposits of the Great Lakes. Instead, the deposits retain the typical characteristics of wave‐dominated, pure gravel and mixed sand and gravel beaches, there including the classical subdivision of infill zone, swash zone/sand run, imbricated zone, coarse flat‐clast zone and coastal dunes. These zones form a regular succession on the surface of many modern beaches; however, they seldom occur as quasi‐complete vertical successions in older deposits. In the studied uppermost Pleistocene deposits, the various components are separated vertically by erosional contacts (bounding surfaces) readily recognizable on working faces of large sand and gravel pits and mappable in the subsurface by ground‐penetrating radar. The lithofacies are sufficiently diagnostic to allow recognition of depositional settings, and the lithofacies architecture allows the deciphering of important geological events, such as: (i) local input of fluvial material onto the shoreface, where it was partially reworked by waves and moved onto the beachface; (ii) occurrence of major storm events; and (iii) repeated rapid transgressions and regressions typical of the glacial‐lake precursors of the modern Great Lakes.

Delta formations associated with high-frequency (annual?) lake-level fluctuations: An example from the uppermost Pleistocene Gokarna Formation, Kathmandu Valley, Nepal

Delta formations associated with high-frequency (annual?) lake-level fluctuations: An example from the uppermost Pleistocene Gokarna Formation, Kathmandu Valley, Nepal

Vegetation history and palaeoclimate of the past 30 kyr in Pakistan as inferred from the palynology of continental margin sediments off the Indus Delta

Palynological investigations on a continuous uppermost Pleistocene to Holocene high-resolution gravity core collected from the continental margin off the Indus Delta provide the first, uninterrupted, 30-kyr-long record of vegetation history and palaeoclimate of the Pakistan hinterland. Core analysis and interpretation allows the recognition of (1) greater glacial aridity than during the following postglacial period up to the present day; (2) a significant southward extension of the Himalayan sub-alpine and deciduous hardwood tree zone during the time interval from the Last Glacial Maximum (LGM) to the Younger Dryas cold interval; (3) extreme aridity and climatic deterioration during the LGM and the equivalent to Heinrich event 1; (4) a marked change to early Holocene humid conditions, starting already during the Bölling/Alleröd and increasing abruptly during the Preboreal period; and (5) a gradual reduction of humidity from the middle Holocene to the present. These results are in general agreement with palaeoclimatic reconstructions based on multiple proxies from the Indian subcontinent as well as the Arabian Sea, and especially confirm the occurrence of a clear precipitation maximum in Pakistan between ca. 9 and 7 cal. kyr BP which probably resulted from a combination of increased and prolonged summer (SW) monsoonal strength; both processes ultimately being controlled by orbital changes in northern hemisphere summer insolation and shifts in the position of the Intertropical Convergence Zone.

Incised-valley-fill succession affected by rapid tectonic uplifts: An example from the uppermost Pleistocene to Holocene of the Isumi River lowland, central Boso Peninsula, Japan

The burial history of the Isumi River lowland was reconstructed based on a facies analysis of borehole and geoslicer samples, undisturbed sediment samples collected by 4.0-m-long, 0.35-m-wide, and 0.01- to 0.05-m-deep wedge-shaped steel case, together with an analysis of molluscan shell assemblages for environmental assessment and 14C age measurements. The borehole successions constitute a part of a depositional sequence in a fluvial- and wave-dominated incised valley. The facies succession and age data suggest that the lower part of the succession (before 7.0 calendar kilo years before present (cal. ky BP)) has, in a broad scale, an aggradational to retrogradational stacking pattern, although a short period of sediment progradation occurred during 9.0–8.5 cal. ky BP. The upper part (7.0 cal. ky BP–present) is a prograding succession of beach-shoreface and bayhead delta sediments deposited in an enclosed bay environment (ca. 3.5 cal. ky BP). The facies changes from an open to an enclosed marine environment resulted from barrier formation. Age measurements indicate that the Choja and Izumi terrace surfaces formed some time after 6.5 cal. ky BP and around 3.5 cal. ky BP, respectively. The temporary progradation during 9.0–8.5 cal. ky BP was probably associated with several meters of tectonic uplift, which resulted in an increase in the sediment supply owing to intensified fluvial and marine erosion. After a tectonic uplift at about 6.4 ky BP, a wide strand plain started to form along the bay shore as a result of sediment transport from both north and south of the bay by longshore currents. However, a barrier developed about 3.5 cal. ky BP, after the Izumi Surface was uplifted. Subsequently, this uplift transported sediments probably bypassed the southern part of the lowland and accumulated near the mouth of the bay to form this barrier, as is indicated by the poor strand plain development after this time. Strand-plain progradation might have been prevented by strong wave influences from the Pacific Ocean and longshore currents, resulting from both the recession of the sea cliffs south and north of the lowland and from the uplift, which shifted the shoreline seaward and changed the shoreline environment from an enclosed bay into a more open marine environment.