Late Quaternary Sedimentary Sequences Research Articles

Coupled role of climate and tectonics in the deposition of the late Quaternary sedimentary sequence in the southern margin of the central Ganga Plain, India

ABSTRACT The Ganga Plain’s sedimentation is primarily controlled by Himalayan tectonics, variations in monsoon intensity, and glacier size. However, the significance of intrabasinal tectonics, which is an interplay of the Himalaya tectonics and basement tectonic configuration of the Ganga Plain, in comprehending the late Quaternary Ganga Plain sedimentation remains unclear. In this study, the sediment provenance and extent of weathering experienced by the sediments are studied using the mineralogical and geochemical (major, trace, and rare earth elements) composition of a sedimentary cliff sequence exposed at the Ramnagar locality near the cratonic peripheral bulge in the southern Ganga Plain. In the Ramnagar cliff sediment section, two sediment packages, designated SP-A and SP-B, are identified based on mineralogy, texture, and geochemistry. These packages of sediments show mild chemical weathering and distinct geochemical compositions. The lower part (SP-A) of the Ramnagar cliff section is characterized by higher contributions from mafic sources (pyroxene, feldspar, and mica as dominant minerals), while the upper part (SP-B) is predominately derived from felsic sources (mica and feldspar as dominant minerals), which are supplied via the peninsular and the Himalayan rivers, respectively. The southern part of the central Ganga Plain shows evidence of a shift in the sediment provenance from mafic to felsic source rock at 40 ka. This study demonstrates how weathering and sedimentation are controlled by both regional tectonics and climate in the southern margin of the central Ganga Plain.

Late Quaternary climate change in Australia's arid interior: Evidence from Kati Thanda – Lake Eyre

Williams Point is an iconic late Quaternary sedimentary sequence exposed at the southern margin of Madigan Gulf at Kati Thanda – Lake Eyre (KT-LE), Australia's largest lake. The ∼15 m high cliff outcrop includes 6 m of aeolian sediments, capping a ∼0.5 m beach/shoreline facies containing abundant Coxiella (aquatic gastropod) unconformably overlying 5–6 m of fluvio-lacustrine facies. The base of the outcrop and the playa floor comprises shallow and deeper water laminated lacustrine sediments. We re-examine the stratigraphic sequence using detailed excavations, micromorphological analysis and geochemical characterisation (X-ray fluorescence, X-ray diffraction, palaeoecology, stable isotope analysis of gypsum hydration water and biogenic carbonates, rare earth element analysis) and present a revised chronology using single-grain optically stimulated luminescence (OSL) within a Bayesian framework. Our new chronostratigraphic data generally supports previous interpretations for Williams Point, but crucially refines the timing of several of the key sedimentological units. The deeper-water lacustrine facies on the lake floor, unconformably overlying the Miocene Etadunna Formation, were deposited 206 ± 13 ka (232–169 ka, 95% credible interval; C.I.). A palaeoplaya, or oxidised shallow lake deposits, formed at 153 ± 11 ka (175–131 ka, 95% C.I.) and the uppermost shallow water lacustrine facies at the base of the cliff was deposited at 131 ± 9 ka (150–113 ka, 95% C.I.). An unconformity separates these sediments from the overlying fluvio-lacustrine phase, securely constrained (with eight OSL samples) to 86 ± 4 ka (95–78 ka, 95% C.I.). The isotopic composition of the palaeo-lake water (δ18O and δD), reconstructed from the hydration water of syndepositional gypsum formed in-situ in these fluvio-lacustrine sediments, indicates wetter conditions at 95–78 ka than at ca. 232–131 ka. Based on the provenance analysis these fluvio-lacustrine and lacustrine sediments were sourced from the northern catchments within the Lake Eyre basin but with an additional contribution from the northern Flinders Ranges. An erosional unconformity separates this sedimentary unit from the overlying Coxiella beach facies, which itself dates to 71 ± 4 ka (79–63 ka; 95% C.I.). This beach facies is interpreted to represent a regressional shoreline or near-shore deposit formed during Marine Isotope Stage [MIS] 4. This is the most reliable palaeolake level indicator in the sequence and indicates a maximum water depth of 12 m. The overlying Williams Point aeolian unit (WPAU) dates to 49 ± 4 ka (56–41 ka, 95% C.I.), slightly younger than previous estimates. The modelled age for WPAU overlaps with (and is within uncertainty of) the last KT-LE megalake phase, which reached +5 m AHD at 48 ± 2 ka. However, considering its elevation (−3 to +3 m AHD), the age of this gypsiferous aeolian unit demands that it accreted as KT-LE was entering a playa phase with lengthy periods of exposed lake floor. In turn, this means that the putative Genyornis newtoni (a megafaunal flightless bird) which laid its eggs in the gypsiferous dunes, went extinct during a time of hydrological transformation. These results bring fresh perspectives to a site that has held a heavy sway over previous views of the Quaternary history of Australia's arid zone.

The WASA core catalogue of Late Quaternary depositional sequences in the central Wadden Sea – A manual for the core repository

Abstract The reconstruction of submerged palaeolandscapes and detection of settling surfaces along coastal zones became a major research topic within the last two decades. In this context, the WASA project made use of a multidisciplinary approach for defining the extension and describing the characteristics of the Late Pleistocene to Holocene deposits in the central Wadden Sea region. In addition to sub-bottom transects, more than 140 sediment cores were taken in such an area for stratigraphic reconstruction, making use of multi-proxy analysis. To harmonize these data with the existing regional core database (LBEG archive) a new core catalogue was developed, that allows the identification of the local Late Quaternary sedimentary sequences and their characteristic facies. The WASA core catalogue has been successfully applied for reviewing the published data about the stratigraphic sequence of the Wadden Sea, for a better definition in terms of stratigraphic sequences and spatial extent of the Quaternary geological evolution of the region, and for a detailed reconstruction of the coastal palaeoenvironments.

The Late Quaternary sedimentary sequences and environmental changes based on core studies in the Gavkhouni Playa (Central Iran)

The Late Quaternary sedimentary sequences and environmental changes based on core studies in the Gavkhouni Playa (Central Iran)

Recording Fidelity of Relative Paleointensity Characteristics in the North Pacific Ocean

AbstractNorth Pacific Ocean sediments are important archives of geomagnetic field and paleoenvironmental evolutions, yet late Quaternary sedimentary sequences in the North Pacific Ocean are less explored because of generally low sedimentation rates and the challenge of dating sediments deposited below the calcite compensation depth. Core NP02 sediments from the North Pacific Ocean contain three visible tephra layers, which are identified as the To‐Of, Spfa‐1, and Kt‐3 tephra, respectively. An age model for core NP02 is established based on tephra correlation and one radiocarbon date, which gives a mean sedimentation rate of ∼11.6 cm/kyr. Magnetic analyses suggest the dominance of two remanence carriers; detrital vortex state and biogenic single domain magnetite. Variable depth offsets between the relative paleointensity (RPI) signals carried by the two remanence carriers adds a negligible age error (<0.5 kyr) to the core NP02 RPI record. Pronounced RPI amplitude variations are observed, and the Rockall and Laschamp excursions are identified in the core NP02 RPI record based on the age model. The fidelity of the core NP02 RPI record is further verified by comparison with other RPI stacks and records, and we demonstrate that the RPI variations can assist in chronology refinement.

Refined chronostratigraphy of a late Quaternary Sedimentary sequence from the Yangtze River delta based on K-feldspar luminescence dating

Dating of sediments in the tidal-dominated Yangtze River delta remains a challenge because of extremely complicated processes during sediment transport and deposition in such a fluvial-marine transition zone. To better understand the late Quaternary sedimentary history of the Yangtze River delta, we explore the applicability of K-feldspar luminescence dating techniques to deposits through a case study on a 60-m-long borehole core (YZ07) in the delta and then establish a spanning ~50,000-year-long chronological sequence. A series of luminescence pre-tests, including dose recovery tests and determination of residual dose and fading rates, were implemented using the modified single-aliquot-regenerative dose (SAR) protocol for post-infrared (IR) IR stimulated luminescence (IRSL) measured at 150 °C after prior IRSL at 50 °C (pIRIR150), respectively. Luminescence characteristics of the prior IRSL (IR50) and pIRIR150 were then analyzed to check their validity. Two fading-correction models were utilized to correct apparent ages obtained from IR50 and pIRIR150 signals. The newly obtained K-feldspar luminescence ages were compared with quartz OSL ages and 14C ages. Our results indicate that most of ages derived from pIRIR150 signals were overestimated due to incomplete bleaching; in contrast, the fading-corrected ages from IR50 measured in pIRIR150 protocol are robust as they are consistent with quartz OSL ages and 14C ages as well as the stratigraphy. Additionally, IR50 ages are characterized by negligible residual dose, and thus used for defining chronology of the investigated sequence over the past 50 ka. In combination with sedimentological and paleontological analyses of core YZ07, we find that fluvial to tide-influenced fluvial deposits were emplaced during the period 30–50 ka, which were then overlain by post-glacial tidal-river (13–11.5 ka), and Holocene estuarine-shelf, delta system, and tidal flat deposits in the Yangtze River delta. Together with other chronostratigraphy from the selected cores, we confirm the existence of Marine Isotope Stage (MIS) 3 depositional units along the marginal coast of the Yangtze River delta in relation to the interstadial sea-level highstand. Our stratigraphic correlation based on the refined chronology reveals offshore transition of the MIS 3 unit into facies deposited in deeper and offshore marine environments.

Identification of a late Quaternary alluvial–aeolian sedimentary sequence in the Sichuan Basin, China

The late Quaternary sedimentary sequence in the northwestern part of the Sichuan Basin consists of five lithological units and with increasing depth include the: Chengdu Clay; Brown Clay; Red Clay; Sandy Silt; and basal Muddy Gravel. The genesis, provenance and age of the sediments, as well as the possible presence of hiatuses within this sequence are debated. Measurements of grain-size, magnetic susceptibility, quartz content, quartz δ18O values, element composition, and Sr–Nd isotopic concentrations of samples from a typical sedimentary sequence in the area provides new insights into the genesis and history of the sequence. The new data confirm that the sediments in study site are alluvial–aeolian in origin, with basal alluvial deposits overlain by aeolian deposits. Like the uppermost Chengdu Clay, the underlying Brown Clay and Red Clay are aeolian in origin. In contrast, the Silty Sand, like the basal Muddy Gravel, is an alluvial deposit and not an aeolian deposit as previously thought. Moreover, the succession of the aeolian deposits very likely contains two significant sedimentary hiatuses. Sedimentological analysis demonstrates that the source materials for the aeolian deposits in the northwestern part of the Sichuan Basin and those on the eastern Tibetan Plateau are different. Furthermore, the loess deposits on the eastern Tibetan Plateau are derived from heterogeneous local sources.

Ice-free intervals continuing into Marine Isotope Stage 3 at Sokli in the central area of the Fennoscandian glaciations

An unusually long and continuous Late Quaternary sedimentary sequence has been preserved in a sedimentary basin formed in the Sokli Carbonatite Massif in eastern-central Finnish Lapland. A nearly complete sediment recovery from the central Sokli basin combined with palynological results from sediments not earlier recovered and an independent OSL/AMS 14 C chronology allow us here to define the Late Quaternary climate-stratigra phy at Sokli and describe in detail the environmental record. Three interstadial intervals of Weichselian age are distinguished that correlate with MIS 5c, 5a and part of MIS 3 in the marine oxygen-isotope record. The interstadials of MIS 5c and 3 age are here defined as the Sokli and Tulppio Interstadials, respectively. The MIS 5a interstadial is correlated with the Maaselka/Perapohjola Interstadials of Finnish Lapland, which previously have been tentatively assigned a MIS 5c age. Till beds in the Sokli sequence (deposited during stadials 3– 1) correlate to MIS 5b, 4 and 3/2, respectively. Depositional environments and vegetational changes during the ice-free intervals at Sokli are discussed. The Sokli sedimentary sequence indicates significantly less extensive and more variable ice-cover over Finnish Lapland dur ing the Weichselian than has been earlier suggested based on the long-distance correlation of litho- and bio-stratigraphic fragmentary evidence.

Late Quaternary Paleoshorelines and Sedimentary Sequences in Chabahar Bay (Southeast of Iran)

Chabahar Bay is located along the coast of Sistan province in SE Iran. This area is part of the coastal Makran zone (one of the geological zones of Iran), which had undergone sea-level changes along the Late Quaternary. Due to these processes, multiple sedimentary sequences and several paleoshorelines were created. In this investigation, by using the Geological Information System method, 21 paleoshorelines were recognized. In the borehole at the north of Chabahar Bay, we found 14 layers, which were related to Late Quaternary sedimentary sequences and correlated to glacial and interglacial periods. All layers of borehole were analyzed for grain size, sedimentary structures, and fossil content. Four radiocarbon measurements were done on the lowest and uppermost marine layers of borehole and on C7 and C21 of paleoshorelines. The lowest layer of borehole has 17,600 14C YBP date, related to Cataglacial or Flanderian Transgression, which outcropped at 15 m height and 5,300 m distance to the present shoreline. Sedimentary sequences showed four transgressions and retrogressions occurred from cataglacial to the present. On the other hand, from 4690 ± 40 YBP, 20 paleoshorelines have been created, for which the duration of each may have been about 230 years.

North European last glacial–interglacial transition (LGIT; 15–9 ka) tephrochronology: extended limits and new events

AbstractHigh‐precision correlation of palaeoclimatic and palaeoenvironmental records is crucial for testing hypotheses of synchronous change. Although radiocarbon is the traditional method for dating late Quaternary sedimentary sequences, particularly during the last glacial–interglacial transition (LGIT; 15–9 ka), there are inherent problems with the method, particularly during periods of climate change which are often accompanied by major perturbations in atmospheric radiocarbon content. An alternative method is the use of tephras that act as time‐parallel marker horizons. Within Europe, numerous volcanic centres are known to have erupted during the LGIT, providing considerable potential for high‐precision correlation independent of past radiocarbon fluctuations. Here we report the first identification of the Vedde Ash and Askja Tephra in Ireland, significantly extending the known provenance of these events. We have also identified two new horizons (the Roddans Port Tephras A and B) and tentatively recognise an additional horizon from Vallensgård Mose (Denmark) that provide crucial additional chronological control for the LGIT. Two phases of the Laacher See Tephra (LST) are reported, the lower Laacher See Tephra (LLST) and probably the C2 phase of the Middle Laacher See Tephra (MLST‐C2) indicating a more northeasterly distribution of this fan than reported previously. Copyright © 2006 John Wiley & Sons, Ltd.

Depositional landforms and environmental change in the headward vicinity of Dias Beach, Cape Point

The southern portion of the Cape Peninsula is characterised by a number of geomorphic features that reveal evidence of fluctuating sea levels and past environments. These include pronounced wave-cut platforms and the remnants of fossilised dunes. This paper reports on a unique Late Quaternary sedimentary sequence preserved within a steep-sided ravine between Cape Point and Cape Maclear at the southern tip of the Cape Peninsula. The site is situated headward of Dias Beach, where erosion has exploited a Cretaceous dolerite dyke that has intruded the Ordovician Table Mountain Group sandstone. The sediments have been incised during the Holocene, and the resultant gullies present exposed faces whose lithostratigraphy attests to a variety of geomorphic processes, which were active during the Late Pleistocene. The two main deposits reveal contrasting sedimentary structures, representing very different depositional environments. Immediately above the active dune cordon, which flanks the modern beach, a sequence of aeolianite (calcarenite) displays a variety of low-angle planar and high-angle cross bedding. This calcarenite is moderately cemented, but not completely lithified. Overlying this sequence, above an abrupt unconformity, is a massive colluvial deposit comprising unconsolidated, quartzose sand, as well as angular sandstone clasts in a number of lags. This deposit does not display any sedimentary structures. The uppermost section of the aeolianite was dated by thermoluminescence to 185 ka. The aeolian lithofacies is interpreted to be the product of aeolian deposition by onshore winds during the transition period following the 220 ka Penultimate Interglacial, the period when sea-level initiated its retreat towards the 150 ka Penultimate Glacial Lowstand. The colluvial deposit is interpreted as the midfan remains of an alluvial/colluvial fan formed by debris flow and sheetwash. Optically stimulated luminescence (OSL) dates from the base (83 ka) and the top (32 ka) of the main fan exposure suggest emplacement during the Last Glacial. Whereas the aeolianite is regarded as the product of an onshore depositional phase, the emplacement process of the colluvial fan suggests the increased presence of moisture. This, in turn, may imply a wetter environment for the southwestern Cape during the Last Glacial. It is known that the Last Glacial was generally drier over the summer-rainfall region of South Africa, but the situation for the present winter-rainfall region remains unclear. The findings from this study support the notion that conditions for the winter-rainfall region of the southwestern Cape may have been wetter prior to the termination of the Last Glacial.

Micromorphological evidence supporting Late Weichselian glaciation of the Northern North Sea

Thirteen samples from three cores and boreholes are examined using micromorphology to test existing interpretations of Late Quaternary sedimentary sequences from the Norwegian Channel, North Sea Fan and the North Sea Plateau. Previous studies have interpreted these sediments using arbitrary parameters as reflecting Late Weichselian subglacial and glacimarine conditions associated with the Scandinavian Ice Sheet and Norwegian Channel ice stream. This study develops existing micromorphological criteria to interpret the samples as reflecting specific processes of subglacial deformation and proximal and distal glacimarine sedimentation during and subsequent to the Last Glacial Maximum. The study concludes by outlining diagnostic criteria for the identification of these sediment types from core and borehole samples of other Quaternary sediments.

All Toba Tephra Occurrences across Peninsular India Belong to the 75,000 yr B.P. Eruption

A controversy currently exists regarding the number of Toba eruptive events represented in the tephra occurrences across peninsular India. Some claim the presence of a single bed, the 75,000-yr-old Toba tephra; others argue that dating and archaeological evidence suggest the presence of earlier Toba tephra. Resolution of this issue was sought through detailed geochemical analyses of a comprehensive suite of samples, allowing comparison of the Indian samples to those from the Toba caldera in northern Sumatra, Malaysia, and, importantly, the sedimentary core at ODP Site 758 in the Indian Ocean—a core that contains several of the earlier Toba tephra beds. In addition, two samples of Toba tephra from western India were dated by the fission-track method. The results unequivocally demonstrate that all the presently known Toba tephra occurrences in peninsular India belong to the 75,000 yr B.P. Toba eruption. Hence, this tephra bed can be used as an effective tool in the correlation and dating of late Quaternary sedimentary sequences across India and it can no longer be used in support of a middle Pleistocene age for associated Acheulian artifacts.

Outflow of the Western Boundary Undercurrent vs 230Th-Excesses in the Late Quaternary Sediments of the NW Atlantic Marginal Basins

Late Quaternary sedimentary sequences collected during two campaigns of the CSS Hudson (90-013 and 91-045) in the North Atlantic marginal basins (30-60~ 50-60~ were analysed for their Th and U isotope contents. They include 21 box cores selected along three transects: i) in the Labrador Sea, from Hamilton Inlet on the Labrador coast, to Cape Farewell, south Greenland, ii) in the Irminger and western Iceland basins, along the 60th parallel, and iii) along the northern edge of the Charlie Gibbs Fracture zone. Five long cores spanning at least the Last Glacial Maximum (LGM)-Present, were also used. They were raised respectively, from the Greenland lower slope (PC-012) and upper rise (PC-013), the Orphan Knoll area (PC-094) and the Iceland basin (P-072; TWC-074). Sedimentological, geochemical, and isotopic studies provided independent chronologies. During the Holocene, very low Holocene sedimentological rates (2 to 5 cm/ka) are observed on the lower slope, i.e. along the high velocity core of the Western Boundary Undercurrent (WBUC) as well as in central parts of the major gyres. They contrast with the much higher rates observed below, on the rise (~> 20 cm/ka) (HillaireMarcel et al. , 1994). A reverse situation prevailed during the Last Glacial Maximum (LGM), when a weaker WBUC resulted in higher sedimentation rates

Paleomagnetic dating of late glacial and postglacial sediments in Lake Superior

The oldest unit of the late Quaternary sedimentary sequence of Lake Superior consists of glacial till that was deposited about 9900 years BP during the last glacial readvance into the Lake Superior basin. The till deposits are unconformably overlain by a thin sequence of bedded sands and silts, which are overlain by a thick sequence of varved sediments (> 10 m in thickness), which in turn are overlain by postglacial silty clays.Unfortunately, 14C has not been found to be a useful tool in dating the late glacial and postglacial sediments of Lake Superior. However, paleodeclination and paleoinclination logs provide a useful method of correlating and indirectly dating cores taken of the late glacial and postglacial sediments. It is concluded from paleomagnetic dating that rhythmic sedimentation ceased before 9200 years BP in the southeastern lake proper and at about 8700 years BP in the southeastern bay areas. However, rhythmic sedimentation continued until about 8200 years BP in the northern part of Lake Superior and until about 8000 years BP in the Nipigon Bay area.

Proglacial sediment instability features on the Scotian Slope at 63°W

A small area of the Scotian Slope has been investigated in detail as a type example of a high-latitude continental slope adjacent to a major ice outlet. The geologic framework has been defined by airgun seismic profiles, which show that Late Tertiary shales have irregular dips, but overlie undisturbed strata. These shales form a zone of diapirs at around 1200 m water depth, which have ponded the prograding Quaternary sediments upslope. High-resolution sparker profiles, SeaMARC I mid-range sidescan imagery, and piston cores have been used to investigate the Late Quaternary sedimentary sequence. A prominent gullied horizon about 40 m subbottom, that is overlain by acoustically unstratified sediments (?sands), is correlated with the occurrence of an early Middle Wisconsinan grounded icesheet at the top of the continental slope. It is overlain by a thick sequence of proglacial muds and a thin veneer of Holocene sediments. Much of the Late Wisconsinan sequence has been dissected by a series of closely spaced gullies. Both sidescan and subbottom profiler data show that slumping is common in the Late Wisconsinan sequence, as a result of high sedimentation rates and local gully erosion. Piston cores provide evidence for debris flows and turbidity currents. Depositional sediment mounds in the diapir zone have accumulated sediment at three times the regional sedimentation rate, suggesting that large amounts of fine sediment reached the slope in suspension, and that much of the proglacial sediment by-passed the continental slope.

Late Quaternary Stratigraphy and Prehistory in Wadi Fazael, Jordan Valley: A preliminary Report

A Late Quaternary sedimentary sequence was studied in Wadi Fazael, a major wadi that drains a portion of the Samarian hills into the Jordan Valley. The sequence is represented by alluvial and colluvial deposits and periods of erosion that separate the aggradational episodes. The sediments contain prehistoric remains related to the Mousterian, Kebaran, Geometric Kebaran A and Natuflan. The types and patterns of sedimentation seemed to have been influenced primarily by climatic fluctuations interpreted geochronologically as follows : Deposition of gravels and travertines during a Mousterian wet period is followed by erosion. Later, an alluvial episode (dated by Kebaran sites) represents a wet period, less intensive than the Mousterian one, and is succeeded by a period of erosion. Continuous colluviation during Geometric Kebaran A through Late Natuflan designate progressive dessification. This interpretation is supported by preliminary pollen analyses.