Quaternary Sedimentary Sequence Research Articles

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

Recent developments in luminescence dating of Quaternary sediments

Luminescence dating is an important technique for providing chronological control for Quaternary sedimentary sequences. In this article recent developments in luminescence dating are described, together with the implications of these developments for the application of the various types of luminescence dating techniques now available. In particular, the development of optically stimulated luminescence (OSL) techniques has had a profound effect upon the field, enabling younger materials to be dated, increasing the diversity of depositional environments that can be dated, and allowing the development of novel methods of age determination. The most exciting developments are the ability to obtain luminescence ages for samples in the age range from 100 to 1000 years, and the ability to date individual sand grains from a sample.

Late Neogene Radiolarian Biostratigraphy in the Subarctic Northwest Pacific

Late Neogene Radiolarian Biostratigraphy in the Subarctic Northwest Pacific

The Darss Sill, hydrographic threshold in the southwestern Baltic: Late Quaternary geology and recent sediment dynamics

About 73% of the water exchange between the Baltic and the North Seas is via the Darss Sill. Joint Danish and German marine geological investigations, including shallow seismic surveys and sediment sampling, have been carried out in the Darss Sill area between 1989 and 1991. Results from these studies and unpublished archive data from the Institute of Baltic Sea Research, Warnemünde, are presented. These show that the entire Quaternary sedimentary sequence in most of the area is at least 40 m thick. A zone of glacial till outcropping between Denmark and Germany belongs to the Late Weichselian ice marginal line G (“Velgaster Staffel”). The formation of this line caused the damming of a pre-existing (sub)glacial meltwater discharge system. At the beginning of the Baltic Ice Lake formation, a deep and presently buried channel incised in this ice marginal line was part of a (glacio)fluvial drainage system with discharge towards the northeast, i.e. into the Baltic Ice Lake. During the Baltic Ice Lake transgression damming of the Darss Sill occurred due to accumulation of sandy sediments within this channel. On the other hand, the recent Kadet Channel was only occasionally overflown during the Baltic Ice Lake highstand maximum, which was 18 m BSL (below present sea level) in the Darss Sill area. The main erosion and deepening of the Kadet Channel began during the Ancylus Lake highstand maximum. At present, sediment transport on the Darss Sill is governed by northeasterly inflow of saline bottom waters in the entire area from the Kadet Channel to the German coast. Baltic outflow affects the seabed at shallower depth in the Danish sector. Large-scale current-induced bedforms in the area include, amongst others, sandwaves with a height of 5 m. Changes of the bedforms observed indicate a maximum bottom flow speed of 70–100 cm s −1, both for inflow and for outflow.

Offshore Quaternary sediments and their engineering significance in Hong Kong

Yim, W.W.-S., 1994. Offshore Quaternary sediments and their engineering significance in Hong Kong. In: E.F.J. de Mulder (Editor), Engineering Geology of Quaternary Deposits. Eng. Geol., 37: 31–50. Investigation works undertaken for coastal engineering projects in Hong Kong has provided abundant information on the Quaternary sedimentary sequence beneath the sea floor. Although the significance of such information may not have been realized at the time of these projects, valuable lessons have often been learnt afterwards. Some examples of the important engineering applications concerning offshore Quaternary sediments include: (1) The provision of information on water movement, sediment transport and sedimentation rates during the Holocene period. (2) The identification of exploitable offshore sand and gravel resources. (3) The interpretation of marine geophysical data through the availability of reliable borehole descriptions. (4) The enhancement of engineering soil testing results and their interpretation. (5) The prediction of rates of long-term ground settlement in coastal land reclaimations. (6) The selection of offshore sites for waste disposal. (7) The reduction in cost of coastal engineering projects through choosing the most cost-effective site. (8) The provision of baseline data to assist environmental impact assessment. A new geological model is proposed for the offshore Quaternary sedimentary sequence of Hong Kong. The engineering properties of the sediments are found to be closely related to the palaco-environmental changes.

Late Quaternary record of sea-level changes in the Antarctic

The Late Quaternary sediment sequence of the continental margin in the eastern Weddell Sea is well suited for palaeoenvironmental reconstructions. Two cores from the upper slope, which contain the sedimentary record of the last 300 ky, have been sedimentologically investigated. Age models are based on lithostratigraphy and are correlated with the stable isotope record. As a result of a detailed analysis of the clay mineral composition, grain size distributions and structures, this sedimentary record provides the first marine evidence that the Antarctic ice sheet extended to the shelf edge during the last glacial. The variations in volume and size of the ice sheet were also simulated in numerical models. Changes in accumulation rate and ice temperature are of some importance, but the model revealed that fluctuations are primarily driven by changes in eustatic sea-level and that the ice edge extended to the shelf edge during the last glacial maximum. This causal relationship implies that the maximum ice extension strongly depends on the magnitude and duration of the sea-level depression during a glacial period. The results of the sedimentological investigations and of the numerical models show that the Antarctic ice sheet follows glacial events in the northern hemisphere by teleconnections of sea level.

Late Cenozoic stratigraphy and hydrologic history of Lake Amadeus, a central Australian playa

This study of stratigraphy, chronology and sedimentology at Lake Amadeus, a major playa lake in central Australia, provides for the first time a Late Tertiary and Quaternary sedimentary sequence from the continent's centre. The Cenozoic sediments of the lake basin consist of two major units: the Uluru Clay; and the overlying Winmatti Beds. At least 60 m of Uluru Clay overlies Proterozoic dolomitic limestone and consists of uniform clay horizons with minor intercalated gypsum. The clay was deposited in a shallow lacustrine and fluvial environment. Conditions were periodically saline and frequently dry. The basal Uluru Clay is estimated to be over 5 Ma old. The Winmatti Beds, comprising the top several metres of basin sediments, are characterized by aeolian sand, gypsum‐clay laminae and thick gypsum sands. The dominance of saline groundwater marks the first development of a groundwater discharge playa system. The association with aeolian deposits signals, for the first time, the dominance of major aridity. ...

Nonmarine ostracods as Quaternary palaeoenvironmental indicators

Ostracods are small, bivalved crustaceans with calcitic shells that are often well preserved in Quaternary sediment sequences. Although ostracods are found in most types of water body, work on Quaternary faunas has focused on marine environments. This paper, however, reviews the significant contribution that ostracods have also made to the study of nonmarine environments, particularly lakes. Although much of the early work on ostracods was taxonomic, recent studies have dramatically improved our understanding of ostracod ecology. Aquatic chemistry, in particular, has been shown to be an important control on the occurrence of nonmarine species. However, data are still lacking from many parts of the world and for many species. A knowledge of such controls is vital if ostracods are to be used as palaeoenvironmental indicators. An exciting development over the past decade has been the use of ostracod shell chemistry as a palaeoenvironmental tool. The stable isotope composition of the shell has been used in a number of studies to provide important information on palaeohydrology and palaeoproductiv ity of lakes. Furthermore, the trace-element geochemistry of ostracod shells has been used most successfully as a palaeosalinity and palaeotemperature indicator. Although nonmarine ostracods have yet to be used routinely as Quaternary palaeoenvironmental indicators, it is clear that they will play an increasingly important role with the collection of more ecological data and the development of new techniques.

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.

Dinoflagellates, their cysts and Quaternary stratigraphy.

Dinoflagellates are described, with particular emphasis on their feeding strategies and role within the phytoplankton. The potential ecological value of the fossilizable hypnozygotic cyst in reconstructing the climate throughout the Quaternary marine record is noted. Dinoflagellate cysts can be used to detect changing climates in marine Quaternary sediment sequences as pollen is used for continental Strata. The unique capacity of dinoflagellate cysts in effecting correlations from the deep ocean to the inner shelf is of potential importance.

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.

Deformation of Scottish Quaternary sediment sequences by strong earthquake motions

Summary Deformed Quaternary sand, silt, clay and peat sequences from four localities in Scotland are interpreted as seismites by the deformation history of liquefied, fluidized, slumped, and faulted units, and by comparison with seismites documented elsewhere. Two of the sequences consist of outwash sands and silts, deposited during the recession of the Devension ice cap in the region of Perth. Other deposits consist of glacial sands and interglacial peats in the Western Highlands, and glacio-lacustrine silts in the Glen Roy area; both probably deposited during the late stages of the Loch Lomond Readvance. Careful evaluation of internal geometries and deformation sequences reveals an intimate association of ball-and-illow, fluidization, dish, load, flame and ‘fault-grading’ structures which are most satisfactorily explained by prolonged ground shaking produced by shallow earthquakes. In some cases, potential fault sources for the inferred earthquakes have been identified.

Soils and Quaternary Landscape Evolution

This book examines a period of spectacular environmental change, the Quaternary, with respect to soil-landscape relationships in Western Europe, the British Isles and North America. The possibilities for using soils as climatic indicators in the same way as fossils are discussed. The major themes emerging from the book are: the importance of soil stratigraphy in understanding Quaternary sedimentary sequences; the problems of soil-dating and the significance of soil colour; and the growing realisation of the importance of cold-climate processes in soil formation in Western Europe.

The Quaternary deposits and landforms of Scotland and the neighbouring shelves: A review

A thick sequence of Quaternary sediments (up to 1000 m) has been deposited in the North Sea Basin and perhaps five major glacial episodes, the first occurring prior to ca. 1.8–2.1 Ma BP and the last during the Late Devensian, can be recognised. Between the glacial events periods of low salinity arctic marine or glacio-marine sedimentation have been dominant although episodes of ameliorated climate when North Atlantic Drift waters had access to the North Sea have been identified. A number of horizons in separate boreholes have been correlated with the last interglacial (oxygen isotope stage 5e) and a sequence of water mass movements around the Scottish coasts can be reconstructed for the last ca. 125 ka. On land, sequences of Quaternary deposits relating to several glacial and non-glacial (terrestrial and marine) events occur in different areas but due to poor dating correlation between these sequences cannot yet be achieved. In particular, North-East Scotland has a complex glacial history with evidence for ice sheet glaciation on at least four occasions. Evidence from the Outer Hebrides, North-East Scotland and the North Sea Basin indicates that the Late Devensian Scottish ice sheet had a rather restricted extent, only reaching a short distance offshore along much of the east and west coasts. At this time ice free areas existed in North-East Scotland, on the Isle of Lewis and, probably, in Caithness and Orkney, whilst part of the outer shelf around St Kilda was dry land. A marine embayment extended down the east coast of Scotland between the Scottish and Scandinavian ice sheets and independent ice caps existed on the Outer Hebrides and probably on Shetland. Deglaciation of the greater part of the country took place prior to ca. 13 ka BP whilst the climate was still very cold. The ice retreat appears to have been orderly with stagnant ice masses being trapped only in topographically suitable locations. A number of retreat stages or minor readvances occurred during the general deglaciation. The Firth of Clyde was one of the last areas outside the Highlands to be deglaciated and this occurred in a rapid, possibly catastrophic, fashion shortly prior to ca. 13 ka BP. Despite the mild climate at the start of the Lateglacial Interstadial it is not known if there was complete deglaciation prior to the Loch Lomond Readvance. The Readvance glaciers, however, may have started to advance during the latter part of the Interstadial when declining terrestrial temperatures coincided with a period of mild marine conditions. The Loch Lomond Readvance maximum can only be dated to some time after ca. 10.9 ka BP and it is likely that final ice free conditions were not achieved until the earliest Holocene.

Late Quaternary sedimentation in a zone of continental plate convergence — The central Hellenic Trench system

The central Hellenic Trench system, south of Crete, is a tectonically active region forming part of a complex geotectonic regime involving continental plate collision and convergence. Gravity and piston cores, together with seismic reflection profiles, provide evidence of significant variations in Plio-Quaternary lithology and sediment geometry that broadly reflect the morphologic diversity of this area and yield data important in the elucidation of analogous ancient sequences. Gravitite sediments are typically found in the trenches and deep basins, while suspensite sediments predominate on highs and in some perched basins. In detail, the trench floors are characterized by cyclic repetitions of gravitite sediments (in high proportions, comparable only to submarine fans elsewhere in the Mediterranean), thick diluted sapropels and hemipelagic calcareous oozes. The substantial core-to-core variations in this and other facies assemblages are attributed to the variety of sub-environments present within each depositional province. The Late Quaternary sediment sequences present in cores are well organized and display a cyclic stratigraphy that can be correlated with other eastern Mediterranean areas. Sedimentation rates deduced on the basis of this correlation are noticeably lower than in the western Hellenic Trench or the Nile Cone, probably because of the reduced supply of fine-grained terrigenous material to this area. Although there is a marked correlation between the Late Quaternary climatic-eustatic oscillations and the sediment types and rates, some of the overall variations in lithofacies patterns are best attributed to the tectonic mobility of the area. Seismic profiles reveal substantial regional variations in the geometry and organization of the Plio-Quaternary sedimentary fill in adjacent sectors of the trenches. The thickness of unconsolidated, undeformed sediment below the trench floor is also much smaller than that extrapolated from the Late Quaternary sedimentation rates computed from the cores. It is concluded that these variations in geometry and thickness of the sedimentary infill reflect different stages in the process of convergence and plate consumption. The differential removal of sediments from adjacent sectors of the trench floor is further interpreted as a discontinuous and diachronous process. The geometry, thickness and lithofacies represented in the central Hellenic Trench sequences appear more varied and complex than those reported from modern Pacific trenches and it is suggested that the Quaternary sediments of this region may furnish more appropriate examples of the deposition associated with alpine-type compressional settings than the sedimentary fill of Pacific-type trenches.

Three late-Devensian sites in West-central Scotland

PRELIMINARY investigations of late-Devensian sediments that include moss-sedge peat and moss detritus suitable for radiocarbon dating indicate movement of thick layers of till on the sides of drumlins in west-central Scotland since ∼11,150 b.p. Two of the sites investigated are in inter-drumlin depressions on the north-eastern side of Glasgow: at Springburn (NS 609678) and Robroyston (NS 633676). The third site is between Paisley and Irvine on the floor of the Lochwinnoch Gap at North Kerse (NS 339556). The Quaternary sedimentary sequences at the three sites are shown in Fig. 1.

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.