Late Quaternary History Research Articles

Paleoearthquakes and Eolian-Dominated Fault Sedimentation along the Hubbell Spring Fault Zone near Albuquerque, New Mexico

The Hubbell Spring fault zone forms the modern eastern margin of the Rio Grande rift in the Albuquerque basin of north-central New Mexico. Knowledge of its seismic potential is important because the fault zone transects Kirtland Air Force Base/Sandia National Laboratories and underlies the southern Albuquerque metropolitan area. No earthquakes larger than M L 5.5 have been reported in the last 150 years in this region, so we excavated the first trench across this fault zone to determine its late Quaternary paleoseismic history. Our trench excavations revealed a complex, 16-m-wide fault zone overlain by four tapered blankets of mixed eolian sand and minor colluvium that we infer were deposited after four large-magnitude, surface-rupturing earthquakes. Although the first (oldest) rupture event is undated, we used luminescence (thermoluminescence and infrared-stimulated luminescence) ages to determine that the subsequent three rupture events occurred about 56 ± 6, 29 ± 3, and 12 ± 1 ka. These ages yield recurrence intervals of 27 and 17 k.y. between events and an elapsed time of 12 k.y. since the latest surface-rupturing paleoearthquake. Slip rates are not well constrained, but our preferred average slip rate since rupture event 2 (post-56 ka) is 0.05 mm/yr, and interval slip rates between the last three events are 0.06 and 0.09 mm/yr, respectively. Vertical displacements of 1–2 m per event and probable rupture lengths of 34–43 km indicate probable paleoearthquake magnitudes ( M s or M w) of 6.8–7.1. Future earthquakes of this size likely would cause strong ground motions in the Albuquerque metropolitan area.

Peatlands of the Western Siberian lowlands: current knowledge on zonation, carbon content and Late Quaternary history

The Western Siberian lowlands (WSL) are the world's largest high-latitude wetland, and possess over 900,000 km 2 of peatlands. The peatlands of the WSL are of major importance to high-latitude hydrology, carbon storage and environmental history. Analysis of the existing Russian data suggests that the mean depth of peat accumulation in the WSL is 256 cm and the total amount of carbon stored there may exceed 53,836 million metric tons. A synthesis of published and unpublished radiocarbon dates indicates that the peatlands first developed at the end of the Last Glacial, with a rapid phase of initiation between 11,000 and 10,000 cal yr BP. Initiation slowed after 8000 cal yr BP and reached a nadir at 4000 cal yr BP. There has been renewed initiation, particularly south of 62°N, following 4000 cal yr BP. The initial development of peatlands in the WSL corresponds with the warming at the close of the Pleistocene. Cooling after 4000 Cal yr BP has likely led to increased permafrost and increased peatland development particularly in central and southern regions. Cold and dry conditions in the far north may have inhibited peatland formation in the late Holocene.

Late-Quaternary history of the alpine flora of the New Hampshire White Mountains

A distinctive flora of 73 species of vascular plants and numerous bryophytes occurs in the ca. 20 km 2 of alpine tundra in the White Mountains, New Hampshire. The late- Quaternary distribution of these plants, many of which are disjuncts, was investigated by studies of pollen and plant macrofossils from lower Lakes of the Clouds (1 542 m) in the alpine zone of Mount Washington. Results were compared with pollen and macrofossils from lowland late-glacial deposits in western New England. Lowland paleofloras contained fossils of 43 species of vascular plants, 13 of which occur in the contemporary alpine flora of the White Mountains. A majority of species in the paleoflora has geographic affinities to Labrador, northern Québec, and Greenland, a pattern also apparent for mosses in the lowland deposits. The first macrofossils in lower Lakes of the Clouds were arctic-alpine mosses of acid soils. Although open-ground mosses and vascular plants continued to occur throughout the Holocene, indicating that alpine tundra persisted, fossils of a low-elevation moss Hylocomiastrum umbratum are evidence that forest (perhaps as krummholz) covered a greater area near the basin from 7 500 to 3 500 yBP. No calcicolous plants were recovered from sediments at lower Lakes of the Clouds. Climatic constraints on the alpine flora during the Younger Dryas oscillation and perhaps during other cold-climate events and intervening periods of higher temperature may have led to the loss of plant species in the White Mountain alpine zone. Late-glacial floras of lowland western New England were much richer than floras of areas above treeline during late-glacial time and at the present.

Tectonically driven landscape development within the eastern Alpujarran Corridor, Betic Cordillera, SE Spain (Almerı́a)

The Betic Cordillera is a topographic manifestation of Miocene to recent collision between the African and the European plates. Mountain ranges in the Internal Zone of the Betic Cordillera are exhumed massifs of metamorphic and sedimentary rocks, and are surrounded by low-lying sedimentary basins. The Neogene history of mountain range uplift and basin formation in the Betics is well studied, but Quaternary topographic development and its relation to convergent plate boundary tectonics is less understood. Deformation, rates of stream incision and factors controlling landscape evolution on the flanks of the highest mountains in the Betic Cordillera are studied to gain insight on the relationship of Quaternary tectonics to topographic development. Specifically, geomorphic processes that led to formation of topographic relief within the Internal Zone of the Betic Cordillera are assessed. This paper is based on a field study conducted in the eastern Alpujarran Corridor (EAC), which is the eastern half of a 4–6-km wide and 80-km long inverted sedimentary basin. The Mid to Late Quaternary history of basin denudation is deduced on the basis of morphostratigraphic, geochronologic and structural–geologic analyses of oxygen isotope Stage 8-time fluvial deposits in the EAC. Results of these analyses indicate that climate and faulting played only a minor role in landscape evolution in the EAC. Instead, the EAC topographic trough was excavated by a drainage network whose axial stream (Rı́o Andarax) was incising at a rate between 0.3 and 0.7 m/ka since oxygen isotope Stage 8. This paper demonstrates that these incision rates are the same as regional rock uplift rates in the EAC. During the Mid and Late Quaternary, topographic relief between the EAC and adjacent mountain ranges developed largely as a result of fluvial denudation driven by regional uplift. The implications of the results of this investigation are used to propose a model of Quaternary topographic relief development in the Internal Zone of Betic Cordillera. Topographic relief between Internal Zone bedrock massifs and adjacent basins formed largely as a result of fluvial denudation driven by regional uplift. Faulting also played a significant role in areas that are within a few kilometers of crustal-scale fault zones.

Late Quaternary history of Washington Land, North Greenland

During the last glacial stage, Washington Land in western North Greenland was probably completely inundated by the Greenland Ice Sheet. The oldest shell dates from raised marine deposits that provide minimum ages for the last deglaciation are 9300 cal. yr BP (northern Washington Land) and 7600 cal. yr BP (SW Washington Land). These dates indicate that Washington Land, which borders the central part of Nares Strait separating Greenland from Ellesmere Island in Canada, did not become free of glacier ice until well into the Holocene. The elevation of the marine limit falls from 110 m a.s.l. in the north to 60 m a.s.l. in the southwest. The recession was followed by readvance of glaciers in the late Holocene, and the youngest shell date from Neoglacial lateral moraines north of Humboldt Gletscher is 600 cal. yr BP. Since the Neoglacial maximum, probably around 100 years ago, glaciers have receded. The Holocene marine assemblages comprise a few southern extralimital records, notably ofChlamys islandicadated to 7300 cal. yr BP. Musk ox and reindeer disappeared from Washington Land recently, perhaps in connection with the cold period that culminated about 100 years ago.

Late Quaternary history of Washington Land, North Greenland

Late Quaternary history of Washington Land, North Greenland

Late Quaternary history of the Marmara Sea and Black Sea from high-resolution seismic and gravity-core studies

Lithologic and multi-proxy paleoenvironmental data from 21 dated cores have been used to define three allostratigraphic units (allounits) within the late Quaternary successions of the Marmara Sea and Black Sea. Allounits are bounded by unconformities and their correlative conformities. In both regions, Allounit A extends from the seafloor downward to a ∼12–11-ka sequence boundary, which is a major shelf-crossing unconformity in water depths less than ∼100–110 m. In deep basins of the Marmara Sea, the lower part of Allounit A, designated Subunit A2, is a laminated sapropel, M1. On the shelf, Subunit A2 consists of backstepping delta lobes and early-transgressive barrier islands and sand sheets. Allounit B has only been recovered in Marmara Sea cores collected at water depths greater than ∼90 m, and represents basinal or prodeltaic deposition during the 23–12-ka late Pleistocene lowstand. During the last glacial maximum, the shelves surrounding the Marmara Sea were subaerially exposed, and deltas of Allounit B accumulated along the present-day shelf edge. Following the post-glacial rise of global sea level to −75 m at ∼12 ka, the Marmara Sea quickly became inundated and thereafter rose in synchroneity with the Mediterranean. By ∼10 ka, the Black Sea rose to start spilling into the Marmara Sea, leading to establishment of a brackish-water lid that has persisted to the modern day. The strongest Black Sea outflow began at ∼10 ka and persisted to ∼6 ka, promoting the accumulation of sapropel M1 in the deep Marmara Sea, and progradation of an overflow delta just south of the exit from the Bosphorus Strait. Allounit C is a laminated sapropel (M2) in basinal cores, dated at ∼30–23 ka. Like M1, it is believed that M2 accumulated during a period of increased brackish-water input into the Marmara Sea mainly from the Black Sea. In the Black Sea, wave erosion kept the shelf stripped of unconsolidated sediments during the falling sea level associated with the last glaciation and subsequent early stages of the post-glacial Holocene transgression. This erosion created a major unconformity, α. Shelf-edge deltas of Allounit B received their sediment during the last lowstand from small rivers that likely coalesced into a single system toward the shelf edge, at modern water depths of −100 to −110 m. These deltas were active until ∼11–10.5 ka. Subsequently, sea level in the Black Sea rose to −40 m by ∼10 ka, and a set of backstepping barrier islands developed on the shelf as part of the associated transgressive systems tract. Once water level reached −40 m, continued sea-level rise stalled until ∼9 ka as the Black Sea began to spill across the Bosphorus Strait into the Marmara Sea.

Late Quaternary history of spruce in southern Europe

The late Quaternary history of fossil spruces in southern Europe ( Picea abies (L.) Karsten and Picea omorika (Pancic) Purkyne) is based on 163 selected pollen, charcoal and macrofossil records. The timing of immigration of P. abies is estimated from data where the Picea curve passed the threshold value of 4%. P. abies occupied the southern European mountain ranges – excluding the Pyrenees – during the middle part of the last interglacial. Spruce reached its late Quaternary maximum expansion during the early Weichselian, after which it retired from central Europe and expanded in southern Europe during the middle Weichselian interstadials. A general decline in geographical distribution occurred during the last glacial maximum, and populations were most restricted during the Alpine deglaciation. The concept of ‘glacial refugia’ does not apply to residual populations because current climatic reconstructions relate periods of maximum spruce decline to maximum continental dryness during the growth season, rather than to full glacial conditions. Spruce took part in late glacial and early Holocene tree expansions in the eastern Alps and Carpathian, but failed to spread from residual populations in the Apennines and the Pirin–Rila–Rhodopes Mountains. These differences are explained by the influence of oceanic air masses on upper forest belts with relation to geographic location and maximum elevation of mountain ranges. Late glacial spruce expansion in the Alps coincides with the abrupt warming at 14 700–14 500 yr cal BP. High migration rates were reached in the upper forest belts (e.g. 1500–2300 masl) during the early Holocene, and decreased since about 6 kyr cal BP, as a result of climatic cooling during the Neoglaciation (treeline depression), ecological competition with other tree species ( Abies alba), climatic and physical setting of the highest ranges in western Alps, and human impact. The long late Quaternary fossil history of presently isolated spruce stands from the Apennines accounts for their state of genetic differentiation, which could not be fully understood from the shorter time interval of postglacial events.

Late Quaternary distributional stasis in the submediterranean mountain plant Anthyllis montana L. (Fabaceae) inferred from ITS sequences and amplified fragment length polymorphism markers.

Anthyllis montana is a submediterranean, herbaceous plant of the southern and central European mountains. The internal transcribed spacer (ITS) regions of nuclear ribosomal DNA were sequenced from multiple accessions of the species and several closely related taxa. In addition, amplified fragment length polymorphism (AFLP) was analysed from 71 individuals of A. montana collected in 20 localities, mainly in the Pyrenees, Alps, Italian Peninsula and Balkans. Our ITS phylogeny showed a sequential branching pattern in A. montana, implying a western Mediterranean origin followed by an eastward migration. ITS clock calibrations suggest that speciation of A. montana took place at the Pliocene-Pleistocene boundary, while intraspecific divergence dates to Late Quaternary times (i.e. 0.7 million years ago). The AFLP analyses revealed a major genetic (west/east) subdivision within A. montana, probably caused by the massive glaciation of the Alps during this latter time period. The present-day absence of A. montana from vast parts of the Alps, which appear ecologically suitable for the species, together with the finding of evenly distributed AFLP variability within each of the two western and eastern lineages identified, is taken as evidence for a largely static Late Quaternary history without large-scale migration. High levels of AFLP variation observed among populations, together with weak or absent patterns of isolation by distance, seem to be in accord with long-term population insularization and distributional stasis. However, recent small-scale migration and a narrow hybrid zone between western and eastern lineages need to be postulated to explain the intermediate genetic composition of individuals from the Maritime Alps, a well-known suture-zone for other plant and animal species.

Late Quaternary depositional history of the Reuss delta, Switzerland: constraints from high‐resolution seismic reflection and georadar surveys

AbstractGlacial erosion has caused overdeepening of many alpine valleys. After retreat of the ice, they were filled with heterogeneous deposits of glacial, lacustrine and fluvial sediments. A typical example of such a valley segment and its infill is the Reuss delta on the southern shore of Lake Lucerne in Switzerland. To obtain a detailed three‐dimensional image of this valley segment, the ETH Institute of Geophysics has acquired several two‐dimensional, high‐resolution seismic and georadar profiles, and conducted a three‐dimensional georadar survey. Interpretations of these geophysical data were constrained by a geological core extracted from a borehole 300 m deep near the investigation site. The seismic profiles imaged ca. 600 m of sediment infill above bedrock. Based on their reflection characteristics, five different deposition units were distinguished. These units were interpreted as a succession of clay/silt at the base, followed by different sand units with variable but generally increasing amounts of gravel. This succession represented a prograding delta that filled the southern part of Lake Lucerne. The latest fluvial development of the region is best represented by the georadar data. In particular, the three‐dimensional georadar data set provides a detailed view of an ancient braided river channel Copyright © 2002 John Wiley & Sons, Ltd.

Light Fraction Mineralogy of Upper Quaternary Sediments from the Saint Anna Trough and Its Paleoceanographic Interpretation

Distribution patterns of light minerals, including quartz grains with variable roundness degree, is described in three reference cores from the Saint Anna Trough, Kara Sea. The light fraction mineralogy, coupled with our results on grain size distribution and published data on heavy fraction mineralogy, clay mineralogy, foraminiferal assemblages, oxygen isotopy, organic matter, and radiocarbon dating, allows us to reconstruct the Late Quaternary sedimentary history. Three (glacial, glaciomarine, and marine) development stages are distinguished.

Late-Quaternary savanna history of the Colombian Llanos Orientales from Lagunas Chenevo and Mozambique: a transect synthesis

Late-Quaternary savanna history of the Colombian Llanos Orientales from Lagunas Chenevo and Mozambique: a transect synthesis

Late-Quaternary history of midge communities and climate from a tundra site near the lower Lena River, Northeast Siberia

Analysis of midge remains in late-Quaternary sediment, recovered from a lake situated north of treeline in northeast Siberia, indicates the occurrence of notable climatic fluctuations during the last 12 ka. The onset of late-glacial warming was disrupted by a marked cooling event – possibly correlative with the Younger Dryas – that occurred between 11,000 and 10,000 yr BP. Increases in the relative abundance of taxa typically found in tundra lakes, such as Hydrobaenus/Oliveridia and Parakiefferiella nigra, and the concurrent decrease in temperate taxa, such as Microtendipes and Corynocera ambigua, suggest climatic deterioration occurred during this interval. At approximately 10,000 yr BP there was a large increase in temperate taxa such as Microtendipes and C. ambigua, and a decline of essentially all cold-water taxa. This suggests that climate was warmer than present since the modern distribution of both Microtendipes and C. ambigua is limited to forested sites in this region. This warm interval lasted until approximately 6000 yr BP when there was a precipitous decline in temperate chironomid taxa and an increase in cold-water chironomid taxa, such as Paracladius, Hydrobaenus/Oliveridia, Abiskomyia, and Parakiefferiella nigra. This cooling continued through the late-Holocene and the modern tundra chironomid assemblage developed by approximately 1400 yr BP.

Quaternary tectonic warping and strata formation in the southern Osaka Basin inferred from reflection seismic interpretation and borehole sequences

Reflection seismic profiles are used to constrain the late Quaternary history of folding and sedimentation in the southern Osaka Basin in southwest Japan. Seven continuous reflectors are recognized and traced throughout the offshore study area. They are correlated to lithologic boundaries in the Pleistocene Osaka Group whose ages are confirmed in four boreholes. Structure contour maps of dated horizons describe the development of N–S warping in the western portion of the study area, which had occurred at a slow rate from 1.0 to 0.4 Ma. The warping divided the sedimentary basin and controlled the distribution and facies of the Osaka Group. Microfossil assemblages suggest that growth of the warping resulted in the formation of a freshwater lake in the area of present Osaka Bay between 0.5 and 0.4 Ma. Subsequently, the southern Osaka Basin experienced accelerated subsidence produced by northwestward tilting during the Middle and Late Pleistocene.

Late Quaternary lunette dune sedimentation in the southwestern Kalahari desert, South Africa: luminescence based chronologies of aeolian activity

Through the application of luminescence dating techniques, great advances have recently been made in the understanding of the late Quaternary histories of many dryland regions, including southern Africa. Here, this work has largely applied optical dating to sediments from the extensive linear dune systems which dominate the Kalahari region of the central southern African interior. Relatively little attention has been given to localised aeolian accumulations such as lunette dunes, despite their wide distribution over many parts of the region, in particular the arid southwest Kalahari. To redress this, we consider the palaeoenvironmental significance of pan margin lunettes, and investigate the timing of lunette dune development in the southwest Kalahari through the application of optical dating to sediments from lunette dunes associated with four closed basins (pans). Ages show that localised aeolian activity occurred frequently throughout the past 18 ka, indicating that the factors controlling lunette sedimentation are markedly different from those determining regional linear dune development. It is proposed that the mechanisms controlling sediment supply to lunette dunes are controlled at both the regional and local (pan-specific) scales by factors such as groundwater levels. Where pans support more than one discrete lunette, the time since any individual lunette crest received significant accumulations of sediment increases with distance away from the pan margin. Outer and inner lunette sequences may be chronologically disparate features. Inner lunette formation may arise in response to modifications to the local atmospheric boundary conditions by the presence of large, downwind outer lunette features, or by shifts in sediment supply.

Late Quaternary glacial and interglacial environments of the Nechako River - Cheslatta Lake area, central British Columbia

The Quaternary stratigraphy of the Nechako River – Cheslatta Lake area of central British Columbia is described and interpreted to reconstruct the late Quaternary history of the region. Exposures of glacial and nonglacial sediments deposited prior to the last glaciation (Fraser) are limited to three sites. Pollen assemblages from pre-Fraser nonglacial sediments at two of these sites reveal forested conditions around 39 000 BP. During the advance phase of the Fraser Glaciation, glacial lakes were ponded when trunk glaciers blocked some tributary valleys. Early in the glaciation, the drainage was free in easterly draining valleys. Subsequently, the easterly drainage was blocked either locally by sediments and ice or as a result of impoundment of the Fraser River and its tributaries east of the study area. Ice generally moved east and northeast from accumulation zones in the Coast Mountains. Ice flow was influenced by topography. Major late-glacial lakes developed in the Nechako River valley and the Knewstubb Lake region because potential drainage routes were blocked by ice.

Late Quaternary environments in the White Nile region, Sudan

Both the channel of the lower White Nile and the soils adjacent to the river have a number of special characteristics, which are a direct reflection of its unique late Quaternary history. These attributes include a straight channel pattern (despite a flood gradient of 1 in 100 000 and a very fine suspension load) and localised concentrations of buried evaporites, carbonates, and highly saline subsoils at intervals alongside the river. Late Quaternary aeolian, fluviatile and lacustrine deposits in and near the lower White Nile valley reveal a strong contrast between the often dry, cold and windy late Pleistocene climates characteristic of the Last Glacial Maximum (18 000±3000 BP) and the wetter and warmer climates prevalent in those regions towards 11 500–11 000 BP, 9500 BP and 8500–7000 BP. Buried shell-beds and recessional strandlines indicate a sudden and rapid regression of the vastly expanded terminal Pleistocene White Nile in possible Younger Dryas times (11 000–10 000 BP) coinciding with probable temporary closure of Lake Victoria in the Ugandan upper reaches of the White Nile. The stable carbon and oxygen isotopic composition of freshwater gastropod shells in the lower White Nile region is consistent with a stronger summer monsoon towards 11 500–11 000 BP and again towards 8500–7000 BP. At intervals between ca. 18 000 and 12 000 BP, the lower White Nile was a strongly seasonal river, which shifted course frequently and carried large quantities of medium and coarse sand. The present Sudd swamps in the southern Sudan cannot have been in existence during those times, but came into existence (or became reestablished) during the Holocene.

Glacial‐interglacial variability in denitrification in the World's Oceans: Causes and consequences

The late Quaternary history of water‐column denitrifcation of the eastern Pacific margins and the Arabian Sea is reconstructed using sedimentary δ15N measurements. The δ15N values in six piston cores raised from these regions show remarkably similar cyclic variations, being heavy (9–10.5‰) during the interglacials and 2–3‰ lighter during the glacials. This implies that denitrification in these regions decreased substantially during the glacial periods. The glacial decline in denitrification is attributed to reduced upwelling and flux of organic material through the oxygen minimum zone. Since water‐column denitrification in these areas accounts for about half of the fixed‐nitrogen loss in the modern ocean, the inferred decrease in denitrification should have increased the oceanic nitrate inventory during glacial periods. Because nitrate is a limiting nutrient, oceanic productivity and attendant changes in CO2 may therefore have been modulated on glacial‐interglacial timescales by variations in the oceanic NO3 content.

Proglacial lake‐ice conveyors: a new mechanism for deposition of drift in polar environments

Interpretation of sediments in the floors of valleys opening into western McMurdo Sound has been so problematic that it has hindered understanding of the late Quaternary history of the Antarctic Ice Sheet. Lateral moraines and enclosed drift sheets so clearly exposed on the headlands are generally absent within the valleys themselves. Instead, valley‐floor sediments and landforms consist of hummocky, stratified fine sediment generally capped by coarser, poorly sorted material, small cross‐valley and longitudinal ridges, and lateral ridges that superficially resemble shorelines. One clue as to the origin of these deposits is that at least some of the valleys were occupied by large proglacial lakes during the last glacial maximum (e.g. Glacial Lakes Trowbridge and Washburn in Miers and Taylor Valleys, respectively). This paper describes a new mechanism observed in a modern perennially ice‐covered proglacial lake that documents the movement of glacial debris beyond the grounding line across the surface of the lake. This mechanism accounts for the absence of moraines and other ice‐contact features on the valley floors, as well as for the presence of the other deposits and landforms mentioned above.

The palaeolimnology of the Aral Sea: a review

Formerly the fourth largest inland water body in the world, the volume and area of the Aral Sea have decreased dramatically over the past 30 yr largely as a result of human actions. Throughout its approximately 2 million year history the fate of this water body has been intimately linked with that of its two main in-flowing rivers, the Amu Darya and the Syr Darya. We present a review of the hydrological, palaeontological and sedimentological evidence for the evolution of the Aral Sea based largely on Russian literature. Although the structure of the Aral Basin can be traced back to the late Neogene, the Sea has only existed in its present form for the past 8–10 ka and the Holocene history has been shaped by regional climatic variations, the development of the associated drainage system and anthropogenic forces. Past hydrological changes in the Aral Basin have led to systematic shifts in the level of the Aral Sea which are reflected sedimentologically through the deposition of `transgressive’ and `regressive’ sedimentary units and geomorphologically through the development of terraces. All the above data are integrated to produced a Late Quaternary history of this important water body.