Full Glacial Climate Research Articles

Late Pleistocene glaciation in the Eastern Carpathians – a regional overview

The Eastern Carpathians are the northeasternmost sector of the European Alpine Mountain system and comprise 14 formerly glaciated massifs that stretch over 300 km into the territories of Ukraine and Romania. In this study we provide a regional overview on Late Pleistocene glaciation in the Eastern Carpathians integrating recently published and new geomorphological data which include mapped glacial landforms and glacier reconstruction of the maximal ice extent (MIE) which is assigned to the global Last Glacial Maximum (LGM). Thus we obtain a complete inventory of glaciation in the Eastern Carpathians, including the documentation of 214 glacial cirques and 147 small mountain glaciers with a total area of 153.2 km2. The estimated LGM equilibrium line altitude (ELA) shows a strong rise of 2.4 m/km from the northwest (1270 m asl) to the southeast (1870 m asl), as well as a consistent eastward rise on several W-E transects (2–3.4 m/km). Similar patterns are shown by the palaeoglaciation level and the cirque floor altitude trend, which mimic the pattern of modern temperature-precipitation ELA (tpELA) in the region. Reconstructed palaeoglacial trends reflect dominant W-NW precipitation-wind regime and an enhanced zonal North Atlantic circulation pattern in the far interior of Europe in full glacial climate. This is consistent with both regonal palaeoclimatic simulations and wind regime proxies which indicate that the pattern of LGM circulation was similar to the present circulation, although the magnitude may have increased during glacial conditions. Additionally, based on the wide array of glacial landscapes inventoried in this study, ranging from traces of small niche/cirques to about 7 km long valley glaciers, we propose a quantitative approach to define the distinct stages of glacial landscape development based on the relationship between the Pleistocene ELA and mountain hypsometry.

Provenance of loess deposits and stepwise expansion of the desert environment in NE China since ~1.2 Ma: Evidence from Nd-Sr isotopic composition and grain-size record

The Quaternary wind-blown Chinese loess-paleosol sequence, which developed as a product of the intensification of Northern Hemisphere glacial-interglacial cycles, is a major source of information on aridification of the Asian interior. In northeastern (NE) China, extensive loess deposits occur that have great potential for reconstructing the long-term paleoclimatic evolution of the region. Despite existing geochemical data indicate that the probable major source areas for these loess deposits were the nearby Horqin and Otindag deserts, it is still unclear that whether there was a long-term change in the detrital source of these loess deposits. In addition, the aridity history and long-term desert evolution of NE China are currently poorly understood. In the present study, we measured the silicate Nd and Sr isotopic composition of the 28–45 μm grain-size fraction from multiple loess sections (NYZG, SBH, and TDJZ). The results show that the loess deposits of the three sites were dominantly sourced from the Otindag sandy desert and that this source remained constant for the past 1.2 Ma. Notably, the 87Sr/86Sr ratios are influenced mainly by variations in the content of clay-sized material present in the form of aggregates or adhering to the surface of coarser particles. Therefore, caution is needed in the use of 87Sr/86Sr ratios of the 28–45 μm fraction as a tracer of eolian dust, when the clay minerals are not completely removed during the pretreatment process. The grain-size variability of the three sections indicates that stepwise enhancement of aridification in the Otindag sandy desert occurred at 1.2 Ma, 0.9 Ma, and 0.7 Ma, which coincided respectively with the beginning of the Mid-Pleistocene transition (MPT), an extremely cold event at ~0.9 Ma within the MPT, and the establishment of a full glacial climate at the termination of the MPT. This finding supports the hypothesis that the growth of high-latitude ice sheets was the major driver of the long-term aridification of Asian dust source areas.

Late Quaternary vegetation and climate dynamics at the northern limit of the East Asian summer monsoon and its regional and global-scale controls

A late Quaternary pollen record from northern Sakhalin Island (51.34°N, 142.14°E, 15 m a.s.l.) spanning the last 43.7 ka was used to reconstruct regional climate dynamics and vegetation distribution by using the modern analogue technique (MAT). The long-term trends of the reconstructed mean annual temperature (TANN) and precipitation (PANN), and total tree cover are generally in line with key palaeoclimate records from the North Atlantic region and the Asian monsoon domain. TANN largely follows the fluctuations in solar summer insolation at 55°N. During Marine Isotope Stage (MIS) 3, TANN and PANN were on average 0.2 °C and 700 mm, respectively, thus very similar to late Holocene/modern conditions. Full glacial climate deterioration (TANN = −3.3 °C, PANN = 550 mm) was relatively weak as suggested by the MAT-inferred average climate parameters and tree cover densities. However, error ranges of the climate reconstructions during this interval are relatively large and the last glacial environments in northern Sakhalin could be much colder and drier than suggested by the weighted average values. An anti-phase relationship between mean temperature of the coldest (MTCO) and warmest (MTWA) month is documented during the last glacial period, i.e. MIS 2 and 3, suggesting more continental climate due to sea levels that were lower than present. Warmest and wettest climate conditions have prevailed since the end of the last glaciation with an optimum (TANN = 1.5 °C, PANN = 800 mm) in the middle Holocene interval (ca 8.7–5.2 cal. ka BP). This lags behind the solar insolation peak during the early Holocene. We propose that this is due to continuous Holocene sea level transgression and regional influence of the Tsushima Warm Current, which reached maximum intensity during the middle Holocene. Several short-term climate oscillations are suggested by our reconstruction results and correspond to Northern Hemisphere Heinrich and Dansgaard–Oeschger events, the Bølling–Allerød and the Younger Dryas. The most prominent fluctuation is registered during Heinrich 4 event, which is marked by noticeably colder and drier conditions and the spread of herbaceous taxa.

Evolving sources of eolian detritus on the Chinese Loess Plateau since early Miocene: Tectonic and climatic controls

The thick deposits of eolian dust on the Chinese Loess Plateau provide a rare opportunity to explore the past changes of surface processes in response to climatic and tectonic oscillations. Here we report a 22Ma-long Nd and Sr isotopic records of the eolian sources. Decreasing εNd values and increasing 86Sr/87Sr ratios of the eolian deposits has been observed from early Miocene to about 7Ma, which indicates growing material contribution from Qilian Mountains relative to the Gobi Altay Mountains. The source shift during 22–7Ma is interpreted to reflect the erosional response of the Qilian Mountains to its surface uplift. Between 7Ma and 1.2Ma, the results show relative constant Nd and Sr isotopic compositions of the eolian deposits, and thus suggest a constant source contribution between Qilian Mountains and Gobi Altay Mountains. Synchronized uplift of the two mountain ranges during this period may explain the constant ratio of source contribution. Since 1.2Ma, Nd and Sr isotopic records indicate that the relative debris input from Qilian Mountains drops rapidly. As large-scale topographic changes would not be expected in such a short time period, the source shift since 1.2Ma might be by the differing erosional responses in Qilian Mountains and Gobi Altay Mountains to the development of full glacial climate after the middle Pleistocene transition. This work shows that combined Nd and Sr isotopic signatures of the dust records are valuable proxies to monitoring past surface processes on the million years time scale.

Late Quaternary stream piracy and strath terrace formation along the Belle Fourche and lower Cheyenne Rivers, South Dakota and Wyoming

Stream piracy substantially affected the geomorphic evolution of the Missouri River watershed and drainages within, including the Little Missouri, Cheyenne, Belle Fourche, Bad, and White Rivers. The ancestral Cheyenne River eroded headward in an annular pattern around the eastern and southern Black Hills and pirated the headwaters of the ancestral Bad and White Rivers after ~660ka. The headwaters of the ancestral Little Missouri River were pirated by the ancestral Belle Fourche River, a tributary to the Cheyenne River that currently drains much of the northern Black Hills. Optically stimulated luminescence (OSL) dating techniques were used to estimate the timing of this piracy event at ~22–21ka. The geomorphic evolution of the Cheyenne and Belle Fourche Rivers is also expressed by regionally recognized strath terraces that include (from oldest to youngest) the Sturgis, Bear Butte, and Farmingdale terraces. Radiocarbon and OSL dates from fluvial deposits on these terraces indicate incision to the level of the Bear Butte terrace by ~63ka, incision to the level of the Farmingdale terrace at ~40ka, and incision to the level of the modern channel after ~12–9ka. Similar dates of terrace incision have been reported for the Laramie and Wind River Ranges. Hypothesized causes of incision are the onset of colder climate during the middle Wisconsinan and the transition to the full-glacial climate of the late-Wisconsinan/Pinedale glaciation. Incision during the Holocene of the lower Cheyenne River is as much as ~80m and is 3 to 4 times the magnitude of incision at ~63ka and ~40ka. The magnitude of incision during the Holocene might be due to a combined effect of three geomorphic processes acting in concert: glacial isostatic rebound in lower reaches (~40m), a change from glacial to interglacial climate, and adjustments to increased watershed area resulting from piracy of the ancestral headwaters of the Little Missouri River.

Deep-sea pre-glacial to glacial sedimentation in the Weddell Sea and southern Scotia Sea from a cross-basin seismic transect

Abstract Identification of the pre-glacial, transitional and full glacial components in the deep-sea sedimentary record is necessary to understand the ice sheet development of Antarctica and to build circum-Antarctic sediment thickness grids for palaeotopography/-bathymetry reconstructions, which constrain palaeoclimate models. A ~ 3300 km long Weddell Sea to Scotia Sea multichannel seismic reflection data transect was constructed to define the first basin-wide seismostratigraphy and to identify the pre-glacial to glacial components. Seven main seismic units were mapped: Of these, WS-S1, WS-S2 and WS-S3 comprise the inferred Cretaceous–Palaeocene pre-glacial regime (> 27 Ma in our age model), WS-S4 the Eocene–Oligocene transitional regime (27–11 Ma) and WS-S5, WS-S6, WS-S7 the Miocene–Pleistocene full glacial climate regime (11–1 Ma). Sparse borehole data from ODP Leg 113 and SHALDRIL constrain the ages of the upper three seismic units and seafloor spreading magnetic anomalies compiled from literature constrain the basement ages in the presented age model. The new horizons and stratigraphy often contradict local studies and show an increase in age from southeast to the northwest. The up to 1130 m thick pre-glacial seismic units form a mound in the central Weddell Sea basin and in conjunction with the eroded flank geometry, allow the interpretation of a Cretaceous proto-Weddell Gyre bottom current. The base reflector of the transitional seismic unit has a model age of 26.6–15.5 Ma from southeast to northwest, suggesting similar southeast to northwest initial ice sheet propagation to the outer shelf. We interpret an Eocene East Antarctic Ice Sheet expansion, Oligocene grounding of the West Antarctic Ice Sheet and Early Miocene grounding of the Antarctic Peninsula Ice Sheet. The transitional regime sedimentation rates in the central and northwestern Weddell Sea (6–10 cm/ky) are higher than in the pre-glacial (1–3 cm/ky) and full glacial regimes (4–8 cm/ky). The pre-glacial to glacial rates are highest in the Jane- and Powell Basins (10–12 cm/ky). Total sediment volume in the Weddell Sea deep-sea basin is estimated at 3.3–3.9 × 106 km3.

The role of the Nile in initiating a massive dust influx to the Negev late in the middle Pleistocene

The thick deposits of eolian dust on the Chinese Loess Plateau provide a rare opportunity to explore the past changes of surface processes in response to climatic and tectonic oscillations. Here we report a 22 Ma-long Nd and Sr isotopic records of the eolian sources. Decreasing εNd values and increasing 86Sr/87Sr ratios of the eolian deposits has been observed from early Miocene to about 7 Ma, which indicates growing material contribution from Qilian Mountains relative to the Gobi Altay Mountains. The source shift during 22–7 Ma is interpreted to reflect the erosional response of the Qilian Mountains to its surface uplift. Between 7 Ma and 1.2 Ma, the results show relative constant Nd and Sr isotopic compositions of the eolian deposits, and thus suggest a constant source contribution between Qilian Mountains and Gobi Altay Mountains. Synchronized uplift of the two mountain ranges during this period may explain the constant ratio of source contribution. Since 1.2 Ma, Nd and Sr isotopic records indicate that the relative debris input from Qilian Mountains drops rapidly. As large-scale topographic changes would not be expected in such a short time period, the source shift since 1.2 Ma might be by the differing erosional responses in Qilian Mountains and Gobi Altay Mountains to the development of full glacial climate after the middle Pleistocene transition. This work shows that combined Nd and Sr isotopic signatures of the dust records are valuable proxies to monitoring past surface processes on the million years time scale.

Lake Missoula and Its Floods

The city of Spokane lies astride the Spokane River, some 40 miles from its origination near Coeur d’Alene, Idaho. The convention center and hotel, site of the 65th annual meeting of SRM, are located right along the river, creating a beautiful and even idyllic setting. These qualities make it even harder to imagine a long-ago day when a miles-wide wall of water, measuring as much as 500 feet high, bore down on this site. Hours before, a great ice dam on glacial Lake Missoula (present-day Clark Fork River) had failed. The dam was as much as 2,500 feet in height, impounded a lake up to 2,000 feet deep, extended east in the intermontane valleys for 200 miles, and covered some 3,000 square miles. It probably contained over 500 cubic miles of water, approximating half the volume of Lake Michigan. It is now generally agreed that catastrophic fl oods, in accordance with prevailing ice age conditions, repeatedly issued from Lake Missoula, probably on the order of several tens of times. Geologists estimate that the latest and last of the fl oods occurred about 13,000 years ago, creating the observable effects on the ground today, while largely obscuring the effects of earlier fl oods. Most students of the fl oods support that this particular event and its effects should be named “Bretz’s Flood” after the early geologist J Harlen Bretz, who fi rst recognized in 1919 the effects of catastrophic fl ooding on the Columbia drainage of southeastern Washington, as well as the Columbia River Gorge, the Portland-Vancouver Basin, and the Willamette Valley of Oregon. Over the 2 million years of the last ice age, four major glaciations advanced into what is now the northwestern United States. The last of these, the Wisconsin glaciation, left clear evidence of its effects, while likely obscuring most of the evidence of earlier fl ooding. It is near-certain, however, that each of the many fl oods inundated thousands of square miles in what is now central and southeastern Washington to depths of hundreds of feet. Later study also showed that the many fl oods likely shared the same provenance, that is, the same cause and effect. Piecing together the available evidence, it appears that the full glacial climate was cold and dry, with strong winds that redistributed soil materials to the southeastern quadrant of the Columbia Basin. These processes created what is today called the Palouse, an area of wind-deposited silts (loess) over the underlying basalt that had literally oozed out of the earth over previous untold centuries. The winds created dune-like deposits of variable orientation and depth that today make up fertile farmland in southeastern Washington and adjacent Idaho. Bretz’s Flood followed the path of the many earlier fl oods and recreated the effects over thousands of square miles in the Columbia Basin. These can briefl y be considered in four major categories: 1) the channeled scablands, 2) the river canyon, 3) the Grand Coulee, and 4) Lake Lewis.

A multi‐proxy palaeoecological and palaeoclimatic record within full glacial lacustrine deposits, western Tennessee, USA

AbstractThe Fulton Section, along the Mississippi River in western Tennessee, USA, is a 1 km continuous exposure (∼20 m vertically) of Quaternary fluvial and lacustrine deposits, inset within Eocene sediments and buried by thick loess. Fossiliferous slackwater lake sediments record maximum aggradation during the last two major glaciations, with deposition between ca. 190–140 ka and 24– 18 14C ka BP, based on amino acid and radiocarbon chronology, respectively. During the onset of full glacial conditions (ca. 24–22 14C ka BP), a relatively permanent shallow lake environment is indicated by ostracods, aquatic molluscs, and both pollen and macrofossils of aquatic plants. By 21.8 14C ka BP, increasing emergent plants, amphibious gastropods (Pomatiopsis) and heavier δ18O compositions suggest marsh‐like conditions in a periodically drying lake. The surrounding uplands consisted of Picea–Pinus woodlands mixed with cool‐temperate hardwoods (e.g. Quercus, Populus, Carya), grasses and herbs. More open conditions ensued ca. 20 14C ka BP, with loess and slopewash gradually infilling the former lake by 18 14C ka BP. Modern analogue analyses of ostracods and palaeontological evidence imply a full glacial climate similar to today's mixed‐boreal zone in central Minnesota, USA, about 9°C cooler in mean annual temperature than present‐day western Tennessee. Copyright © 2009 John Wiley & Sons, Ltd.

The Taylor Dome Antarctic 18O Record and Globally Synchronous Changes in Climate

The 18O/ 16O profile of a 554-m long ice core through Taylor Dome, Antarctica, shows the climate variability of the last glacial–interglacial cycle in detail and extends at least another full cycle. Taylor Dome shares the main features of the Vostok record, including the early climatic optimum with later cool phase of the last interglacial period in Antarctica. Taylor Dome δ 18O fluctuations are more abrupt and larger than those at Vostok and Byrd Station, although still less pronounced than those of the Greenland GISP2 and GRIP records. The influence of the Atlantic thermohaline circulation on regional ocean heat transport explains the partly “North Atlantic” character of this Antarctic record. Under full glacial climate (marine isotope stage 4, late stage 3, and stage 2), this marine influence diminished and Taylor Dome became more like Vostok. Varying degrees of marine influence produce climate heterogeneity within Antarctica, which may account for conflicting evidence regarding the relative phasing of Northern and Southern Hemisphere climate change.

The Magnitude and Rate of Past Global Climate Changes

The earth's climate is constantly changing and currently warming. This paper is an evaluation of previous climate changes intended to test the validity of assigning causality to human activity. Records of glacial advances and retreats indicate changes in relative summer temperature. Lacustrine and subaerial sediments afford a record of glacier advances and retreats from the end of the Pleistocene. Palynology offers a record of species succession in response to climate changes. Dendrochronology indicates summer temperature. Isotope paleontology provides a measurement of temperature at the time of marine sediment deposition. Isotopic evaluation of continental ice is an indicator of temperature at the time of precipitation. Anthropologic sources provide significant climate data, such as information about villages overrun by glaciers, open-ocean iceberg density, or harbors filled with ice. Available sources record continual changes in climate. The temperature lowered 15 to 20°C from the Paleocene to the Neogene. Another 10°C change occurred in the Pleistocene. Correlative data from North America, Greenland, and Scandinavia indicate many climate changes were global in scope. It is difficult to develop precise paleothermometry, but qualitative evaluations indicate sudden and dramatic changes in climate. Some changes are perhaps as great as a change from conditions warmer than today, to a full glacial climate in as little as 100 years. The converse can be true. Current data indicate a trend of change that is severe but no greater in rate or magnitude, and probably less in both, than many changes that have occurred in the recent geologic past.

Rate and Magnitude of Past Global Climate Changes

Abstract Existing data indicate that the Earth’s climate is probably warming. Politicians and the media typically assume this warming is the result of human activity. This article summarizes previous climate changes to test the validity of assigning causality to human activity. Records of glacial advances and retreats indicate relative summer temperature. Lacustrine and subaerial sediments afford a record of glacier advances and retreats from the Pleistocene to the present time. Palynology offers a record of species succession in response to climate changes. Dendrochronology is another indicator of summer temperature. Isotope paleontology offers a measurement of temperature at the time of marine sediment deposition, and isotopic evaluation of continental ice is an indicator of temperature at the time of precipitation. Anthropologic sources contain significant climate data such as information about villages overrun by glaciers, open-ocean iceberg density, or harbors filled with ice. Today, scientists are capable of direct measurement of climatic conditions. These sources record continual changes in climate. Broadly, the temperature changed 15 to 20°C from the Paleocene to the Neogene. Perhaps, there was as much as another 10°C change in the Pleistocene. Correlative data from North America, Greenland, and Scandinavia indicate many climate changes were truly global in scope. Although it is difficult to develop precise paleothermometry, qualitative evaluations indicate sudden and dramatic changes in climate. Some are perhaps as great as a change from conditions warmer than today to a full glacial climate in as little as 100 years. The converse can be true. Current data indicate a trend of change that is substantially severe but no greater in rate or magnitude, and probably less in both, than many changes that have occurred in the past.

Vegetation history and climate of the last 15,000 years at Laghi di Monticchio, southern Italy

In southern Italy, vegetation contemporary with the end of the last glacial maximum, from 15,000 to 12,000 years ago, is shown by pollen-analysis to have been treeless and steppe-like in character. At 12,500 BP (years before present), Betula (birch) expanded into the steppe, quickly followed by Quercus (oak), Fagus (beech), Tilia (lime) and other tree genera of mesic forest. High percentages of Tilia point to a rich mesic forest that was contemporary with the ‘Allerød’ interstadial of northern Europe. A major decline in mesic trees with an accompanying return of Betula and steppe genera dated to 10,500 years ago identifies a ‘Younger Dryas’ climatic reversal. Betula and steppe genera were replaced by forest of Quercus and other mesic trees, notably Ulmus (elm), as the Holocene began. In the later Holocene, ca. 4000 years ago, Abies (fir), Carpinus betulus (hornbeam) and Taxus (yew) appeared. Abies and Taxus became extinct locally about 2500 years ago, either because of climatic change, or perhaps because of the effects of early agriculture. The Full-glacial climate is thought to have been cold and summer-dry with mainly winter precipitation. The Lateglacial ‘Bølling-Allerød’ Interstadial was summer-wet and warm. The response-surface based climate reconstruction indicates an early Holocene climate with markedly colder winter conditions than today, about −5°C compared with 3.9°C today as a mean temperature for the coldest month. The annual temperature sum is reconstructed as somewhat higher than today, 3500 degree days as compared with a calculated value of 2900 for today. The later Holocene had a climate like today's. Rainfall, and variation in its seasonal distribution, has been a critical determinant of the vegetation cover. The fossil pollen record at Laghi Di Monticchio has been complemented by diatom and plant macrofossil studies which provide evidence of former lake environments as well as data on the upland forest. Lake levels remained high during the Full- and Lateglacial with encroachment of shore vegetation during the Holocene. The sediments also have an exceptionally rich record of tephra falls which are of importance in dating and core correlation. Twenty-one macroscopically visible tephras occur in sediments of the last 15,000 years.

Influence of insolation and glaciation on atmospheric circulation in the North Atlantic sector: Implications of general circulation model experiments for the Late Quaternary climatology of Europe

Atmospheric general circulation models have been used to simulate the sensitivity of regional climates to Late Quaternary changes in insolation, ice sheets and atmospheric CO 2. Model results for full-glacial conditions (18 ka) show the Atlantic Westerly jet strengthened and shifted south, a corresponding southward shift of the Icelandic low and a strengthening and northward shift of the subtropical anticyclone (STA). A glacial anticyclone developed over the European ice sheet and cold, dry conditions prevailed over much of Europe. The full-glacial climate anomaly for the North Atlantic sector is explained by a combination of low atmospheric CO 2 (reducing global surface temperatures) and circulation changes caused by the ice sheets. By the Early Holocene (9 ka) the ice sheets were much reduced while the orbital anomaly was near its maximum, producing mid-continental summer warming and winter cooling and a reduced latitudinal temperature gradient in the northern hemisphere in both seasons. The jet and the Icelandic low were displaced to north of their present position, producing strong onshore flow and mild, wet winters in northern Europe, while the STA was also shifted northwards, producing offshore flow and dry summers in the same region. During the late-glacial transition the effects of insolation and glaciation were antagonistic for some features of the circulation and synergistic for others. The model results suggest palaeoclimatic hypotheses that could be directly tested by comparison with palaeoclimatic data mapped at a synoptic scale.

Full-glacial summer temperatures in eastern North America as inferred from Wisconsinan vegetational zonation

A variety of types of fossil evidence — pollen, macrofossils, and snails — document the occurrence of boreal forest species at low latitudes of eastern North America duringthe last full glacial (18,000 yr B.P.). Both the northern and southern boundaries of boreal coniferous forest are determined by limiting values of summer warmth. Knowledge of these limiting factors permits construction of a gradient of Wisconsinan summer temperatures. The reconstructed temperature departures are 5–12°C for the eastern part of the continent south of the ice, with temperature departures of no less than 5–6°C along the Gulf coast. Information regarding occurrence of tundra and depression of treeline in the Appalachian mountains provides another estimate of summer temperature depression that is in agreement with these results. Comparison with proxy data from other parts of the world shows that the degree of temperature depression is of about the same degree as that postulated for the tropics (Rind and Peteet, 1985; Lui and Colinvaux, 1985) on the basis of the elevational shifts in vegetational zones and snowline. Quantitative estimates of past temperatures (or temperature departures) of the type produced here are valuable because they permit comparison with model simulations of the full-glacial climate. The depression in summer temperatures indicated is lower than most recent modeling results using CLIMAP boundary conditions and adds to suggestions that the reconstructed sea-surface temperatures used as boundary conditions in simulations of glacial and Holocene climates may be in error.

The case for a resident human population in the Central Australian Ranges during full glacial aridity

AbstractThe full glacial climate was marked by enhanced aridity, suggesting that there would be no human occupation of the interior of the continent at the glacial maximum. However, evidence from Puritjarra Rockshelter shows that the Central Australian Ranges continued to be occupied between 22,000 and 13,000 BP. The repeated use of Puritjarra, together with its location away from any natural corridor for travel into the region, indicates the presence of a resident local population. The archaeological evidence is complemented by a model of human ecology in Central Australia at 18,000 BP, showing that there is no a priori reason for expecting the region to have been totally abandoned during the last glacial maximum.

Evidence for a cold, dry full-glacial climate in the American Southwest

Analysis of the evidence concerning full-glacial (27,000–13,000 yr BP) time in the American Southwest has resulted in a reinterpretation of the past climate. After correction for previous errors, which include the use of (1) the July 0°C isotherm as an indicator of modern snowline and (2) relict cirques at the head of heavily glaciated valleys as indicators of past snowline, orographic snowline is estimated to have been about 1000 m lower. This, combined with similar depression estimates for timberline and for cryogenic deposits, results in an annual cooling estimate of 7–8°C. The cooler temperatures caused deposition of coarse “bouldery” alluvial-fan sediments by streams draining areas at high elevations, as well as hill-slope stability, soil development, and subsurface weathering in the lower desert ranges. Reliability of paleoclimatic inferences from water budgets of the extinct paleolakes is questioned on the basis that they exclude groundwater effects. However, recalculation of two water budgets following traditional methods indicates that lowered evaporation rates accompanying a 7–8°C annual cooling would have sufficed to maintain these lakes. Similarly, increased soil moisture would have allowed coniferous woodland to grow ∼700 m lower into the deserts, the maximum recorded by Pleistocene pack rat middens. Therefore, no significant increase in annual precipitation is inferred for full-glacial times.

The Full-Glacial Climate of the Southern High Plains, West Texas

During the last full-glacial on the Southern High Plains of West Texas, the combined amount of precipitation and runoff into the small closed lake basins probably exceeded the present amount by at least 50%: minimum Pleistocene precipitation, based on the present local runoff of 3 inches, was approximately 29 inches; thus, West Texas was subjected to a pluvial climate in the classical sense during the last full-glacial. Pleistocene precipitation could have been less than the present rate and yet sustained the permanent Pleistocene pluvial lakes only if runoff averaged 35% of the precipitation rate. Such a high runoff-to-precipitation ratio occurs only with frequent intense storm activity.

The Geomorphic and Paleoclimatic Significance of Alluvial Deposits in Southern Arizona: A Discussion

Previous articleNext article No AccessDiscussionThe Geomorphic and Paleoclimatic Significance of Alluvial Deposits in Southern Arizona: A DiscussionLawrence K. LustigLawrence K. Lustig Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Geology Volume 74, Number 1Jan., 1966 Article DOIhttps://doi.org/10.1086/627146 Views: 4Total views on this site Citations: 3Citations are reported from Crossref Copyright 1966 the University of ChicagoPDF download Crossref reports the following articles citing this article:Rhodes W. Fairbridge, Charles W. Finkl Tropical stone lines and podzolized sand plains as paleoclimatic indicators for weathered cratons, Quaternary Science Reviews 3, no.11 (Jan 1984): 41–72.https://doi.org/10.1016/0277-3791(84)90004-0G. Robert Brakenridge Evidence for a Cold, Dry Full-Glacial Climate in the American Southwest, Quaternary Research 9, no.11 (Jan 2017): 22–40.https://doi.org/10.1016/0033-5894(78)90080-7 T. M. Oberlander Morphogenesis of Granitic Boulder Slopes in the Mojave Desert, California, The Journal of Geology 80, no.11 (Sep 2015): 1–20.https://doi.org/10.1086/627710