History/Allerød Oscillation

Evolution of temperature is arrowed in the Post-Glacial period according to Greenland ice cores (Bølling-Allerød). Credit: Daniel E. Platt, Marc Haber, Magda Bou Dagher-Kharrat, Bouchra Douaihy, Georges Khazen, Maziar Ashrafian Bonab, Angélique Salloum, Francis Mouzaya, Donata Luiselli, Chris Tyler-Smith, Colin Renfrew, Elizabeth Matisoo-Smith & Pierre A. Zalloua.{{free media}}

The "Allerød Chronozone, 11,800 to 11,000 years ago".

Arizona

Arizona is located at 34°N 112°W.

"The [Younger Dryas boundary] YDB markers, including magnetic grains and microspherules, iridium, soot, and fullerenes with ET helium, are present in the few centimeters just below the black mat at the top of the underlying sediment. This lithologic break represents the surface at the end of the Clovis period before the formation of the black mat. Clovis artifacts, a fire pit, and an almost fully articulated skeleton of an adult mammoth were recovered at Murray Springs with the black mat draped conformably over them. Excavations by Vance Haynes, Jr., and colleagues also revealed hundreds of mammoth footprints in the sand infilled by black mat sediments. These footprints and the mammoth skeleton appear to have been preserved by rapid burial after the YDB event (1). No in situ Clovis points and extinct megafaunal remains have been recovered from in or above the black mat, indicating that the mammoths (except in isolated cases) and Clovis hunting technology disappeared simultaneously."

The "end-Clovis stratum (the YDB) is well dated at Murray Springs, AZ, (eight dates averaging 10,890 ¹⁴
C yr or calendar 12.92 ka) and the nearby Lehner site (12 dates averaging 10,940 ¹⁴
C yr or 12.93 calendar ka). Haynes (2) correlated the base of the black mat (the YDB) with the onset of YD cooling, dated to 12.9 ka in the GISP2 ice core, Greenland [...] (18)."

Wisconsin

Wisconsin is located at 44.5°N 89.5°W.

The Allerød occurred during the last interstadial of the Pleistocene: the Two Creeks Interval of North America.

"Two Creeks Buried Forest provides a unique, precise record of the multiple glacial advances and retreats in this area during the Wisconsinan stage of glaciation. The historic forest became established between the Cary and Valders glacial substages. After temperatures warmed and the Cary glacier retreated northward, a mature boreal-like forest of black and white spruce, hemlock, pine, various mosses and other plants developed in the Two Creeks area near Lake Michigan. Shortly afterwards, the advancing Valders glacier blocked off the northern Lake Michigan drainageway, raising lake levels, flooding the forest and covering the ground with silt and clay, preventing decomposition. Later, when the southern end of the Valders glacier reached the area, it flattened the forest leaving behind another clay layer imbedded with logs and other debris. These layers of clay, silt, sand and the buried forest are visible on a steep bluff along the lakeshore where wave action and erosion have exposed the layers which contain long-buried branches, logs, and stumps of spruce, pine and hemlock trees. Conifer needles, cones, mosses, and terrestrial snails are also present within the layers. Unearthed wood, radiocarbon-dated at 11,850 before present, provides an absolute date on late-glacial sequences in the Lake Michigan Basin, and evidence that periods between substage glacial advances were long enough for forests to develop."

United States

Evidence "from the Hudson Valley and the northeastern U.S. continental margin [...] establishes the timing of the catastrophic draining of Glacial Lake Iroquois, which breached the moraine dam at the Narrows in New York City, eroded glacial lake sediments in the Hudson Valley, and deposited large sediment lobes on the New York and New Jersey continental shelf ca. 13,350 yr B.P. Excess ¹⁴C in Cariaco Basin sediments indicates a slowing in thermohaline circulation and heat transport to the North Atlantic at that time, and both marine and terrestrial paleoclimate proxy records around the North Atlantic show a short-lived (<400 yr) cold event (Intra-Allerød cold period) that began ca. 13,350 yr B.P."

Black Mats

File:Black mat (12.9 ka) Murray Springs Clovis site in Arizona.jpg

The dark line shown is the black mat (12.9 ka) along the arroyo wall of the Murray Springs Clovis site in Arizona. Credit: R. B. Firestone, A. West, J. P. Kennett, L. Becker, T. E. Bunch, Z. S. Revay, P. H. Schultz, T. Belgya, D. J. Kennett, J. M. Erlandson, O. J. Dickenson, A. C. Goodyear, R. S. Harris, G. A. Howard, J. B. Kloosterman, P. Lechler, P. A. Mayewski, J. Montgomery, R. Poreda, T. Darrah, S. S. Que Hee, A. R. Smith, A. Stich, W. Topping, J. H. Wittke, and W. S. Wolbach.{{fairuse}}

File:Map of black mats of Younger Dryas age United States.png

Map of the United States shows 57 locations where one or more sites with black mats of Younger Dryas age occur (filled circles). Credit: C. Vance Haynes, Jr.{{fairuse}}

File:Black mats of Younger Dryas age.jpg

Black mats of Younger Dryas age are from localities in the United States. Credit: C. Vance Haynes, Jr., Glen L. Evans, Vance T. Holliday, Stanley A. Ahler.{{fairuse}}

"A carbon-rich black layer, dating to ≈12.9 ka [in the image on the left], has been previously identified at ≈50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at ≅12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at ≈12.9 ka. This layer also extends throughout at least 15 Carolina Bays [second image down on the left], which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain."

"Most Younger Dryas (YD) age black layers or ‘‘black mats’’ are dark gray to black because of increased organic carbon (0.05–8%) compared with strata above and below (6, 7). Although these layers are not all alike, they all represent relatively moist conditions unlike immediately before or after their time of deposition as a result of higher water tables. In most cases higher water tables, some perched, are indicated by the presence of mollisols and wet-meadow soils (aquolls), algal mats, or pond sediments, including dark gray to black diatomites, at >70 localities in the United States [see map of the United States on the right]. Therefore, black mat is a general term that includes all such deposits, and some YD marls and diatomites are actually white. These latter cases are included in the nearly 30 localities containing strata representing the Pleistocene-Holocene transition (Allerød-Younger Dryas-Holocene) that do not exhibit a black layer because of little or no interaction with ground water or are represented by white to gray diatomaceous strata of YD age [...]. There are both younger and older black layers, but they do not appear to be widely distributed over the continent like the YD black mat, nor are they known to be associated with any major climatic perturbation as was the case with YD cooling."

The map on the right shows "57 locations [...] where one or more sites with black mats of Younger Dryas age occur (filled circles). Open circles are 27 localities with Pleistocene-Holocene transitional sediments but no black mats [...]."

The second image down on the right shows black mats from the following specific locations corresponding to map numbers: "(a) The black mat at the Murray Springs Clovis site in Arizona (locality 1a) is a black algal mat that blankets the Clovis occupation surface. (b) At the Naco Clovis site (locality 1b) the mammoth bones and artifacts are directly overlain by laminated marls and clay bands that are pond facies of the San Pedro Valley black mat. (c) The type Clovis site in Blackwater Draw, New Mexico (locality 5) has a dark-gray diatomite stratum D containing Folsom artifacts and bones of Bison bison antiquus overlying a "brown sand wedge" (stratum C) with Clovis artifacts and mammoth bones over a "gray sand" (stratum B) with Clovis artifacts and bones of mammoth and B. bison antiquus beyond where stratum C pinches out. Photograph courtesy of Glen L. Evans. (d) At the Lubbock Lake site in Texas (locality 6) a black and white diatomite (stratum 2A) [...] contains Folsom artifacts and bones of extinct bison and directly overlies a gray fluvial sand (stratum 1B). Photograph courtesy of Vance T. Holliday. (e) Folsom, Goshen-Plainview, and Agate Basin artifacts are found in situ in the lower portions of the Leonard paleosol at several sites in the Knife River - Lake Ilo region of North Dakota (locality 7). Photograph by Stanley A. Ahler. Published courtesy of the Center for the Study of the First Americans. (f) The Lindenmeier Folsom site in Colorado (locality 8) has Folson artifacts and bison bones covered by a black cumulic mollisol overlying Peoria loess."

Nanodiamonds

A Younger Dryas impact event, may have occurred in North America about 12,900 calendar years ago, that initiated the Younger Dryas cooling.

Among other things, findings of melt-glass material in sediments in Pennsylvania, South Carolina and Syria, which dates back nearly 13,000 years, was formed at temperatures of 1,700 to 2,200 °C (3,100 to 4,000 °F) as an apparent result of a bolide impact that occurred at the onset of the Younger Dryas.

Most of the results cannot be confirmed.

Sediments claimed by hypothesis proponents to be deposits resulting from a bolide impact date from much later or much earlier times than the proposed date of the cosmic impact having examined 29 sites commonly referenced to support the impact theory to determine if they can be geologically dated to around 13,000 years ago, but only three of those sites actually date from then.

The distribution of nanodiamonds produced during extraterrestrial collisions: 50 million square kilometers of the Northern Hemisphere at the YDB have the nanodiamonds. Only two layers exist showing these nanodiamonds: the YDB 12,800 calendar years ago and the Cretaceous-Tertiary boundary, 65 million years ago, which, in addition, is marked by mass extinctions.

Earth may have collided with one or more fragments from a larger (over 100-km diameter) disintegrating comet (some remnants of which have persisted within the inner solar system to the present day), which is consistent with large-scale biomass burning (wildfires) following the putative collision, analyses of ice cores, glaciers, lake- and marine-sediment cores, and terrestrial sequences.

North Carolina

LIDAR elevation image of 300 square miles (800 km²) of Carolina bays is in Robeson County, N.C. Credit: Swampmerchant.{{free media}}

North Carolina is located at 35.5°N 80°W.

The second image down on the left is similar to an aerial "photo (U.S. Geological Survey) of a cluster of elliptical and often overlapping Carolina Bays with raised rims in Bladen County, North Carolina. [...] The largest Bays are several kilometers in length, and the overlapping cluster of them in the center is ≈8 km long. Previous researchers have proposed that the Bays are impact-related features."

"The Carolina Bays are a group of »500,000 highly elliptical and often overlapping depressions scattered throughout the Atlantic Coastal Plain from New Jersey to Alabama (see [second image down on the left]). They range from ≈50 m to ≈10 km in length (10) and are up to ≈15 m deep with their parallel long axes oriented predominately to the northwest. The Bays have poorly stratified, sandy, elevated rims (up to 7 m) that often are higher to the southeast. All of the Bay rims examined were found to have, throughout their entire 1.5- to 5-m sandy rims, a typical assemblage of YDB markers (magnetic grains, magnetic microspherules, Ir, charcoal, soot, glass-like carbon, nanodiamonds, carbon spherules, and fullerenes with ³
He). In Howard Bay, markers were concentrated throughout the rim, as well as in a discrete layer (15 cm thick) located 4 m deep at the base of the basin fill and containing peaks in magnetic microspherules and magnetic grains that are enriched in Ir (15 ppb), along with peaks in charcoal, carbon spherules, and glass-like carbon. In two Bay-lakes, Mattamuskeet and Phelps, glass-like carbon and peaks in magnetic grains (16-17 g/kg) were found ≈4 m below the water surface and 3 m deep in sediment that is younger than a marine shell hash that dates to the ocean highstand of the previous interglacial."

Baffin Island

The Penny Ice Cap is on Baffin Island, Canada, at 67° 15'N, 65° 45'W, 1900 masl.

"Snowpits were excavated in 1994 and 1995."

"The 333.78m. P95 core was drilled to the bed in April-May 1995. The 89m. P95.2 core was drilled adjacent to the P95 core (2.5 m. away) for evaluation of noise in the record. The d18O correlation between the two cores is .80."

"The 177.91m. P96 core also reached the bed. It is located approximately 16 km. from P95. The P95-P96 correlation of d18O on 40-year segments is .3 to .5."

"The P95 core was dated back to 7900 yr ago (319 m) by spectral analysis of the electrical conductivity record which tracks seasonal chemical variations (Fisher et al. 1998; Grumet et al., 1998. Additional time control was provided by conductivity and sulfate peaks related major volcanic eruptions. Beyond 7900 yr ago, the depth-age curve was adjusted to match the end of the Younger Dryas-Holocene transition (326 m) dated at 11,550 +/- 70 yr ago in Greenland ice-core records. Age values for the P95 microparticle record are expressed in years before A.D. 2000 (b2k)."

Greenland

File:Older Dryas.jpg

Comparison of the GRIP ice core with cores from the Cariaco Basin shows the Older Dryas. Credit: Konrad A Hughes, Jonathan T. Overpeck, Larry C. Peterson & Susan Trumbore.{{fairuse}}

NGRIP late Weichselian glacial age Bölling-Alleröd-Younger dryas methane amount data is graphed. Credit: Merikanto, M. Baumgartner, A. Schilt, O. Eicher, J. Schmitt, J. Schwander, R. Spahni, H. Fischer, and T. F. Stocker.{{free media}}

Greenland is located at 72°00'N 40°00'W.

"The most negative δ ¹⁸O excursions seen in the GRIP record lasted approximately 131 and 21 years for the [inter-Allerød cold period] IACP and [Older Dryas] OD, respectively. The comparable events in the Cariaco basin were of similar duration, 127 and 21 years. In addition to the chronological agreement, there is also considerable similarity in the decade-scale patterns of variability in both records. Given the geographical distance separating central Greenland from the southern Caribbean Sea, the close match of the pattern and duration of decadal events between the two records is striking."

In the figures on the right, especially b, is a detailed "comparison of δ ¹⁸O from the GRIP ice core²⁴ with changes in a continuous sequence of light-lamina thickness measurements from core PL07-57PC. Both records are constrained by annual chronologies, although neither record is sampled at annual resolution. The interval of comparison includes the inter-Allerød cold period (12.9-13 cal. kyr BP) and Older Dryas (13.4 cal. kyr BP) events (IACP and OD from a). The durations of the two events, measured independently in both records, are very similar, as is the detailed pattern of variability at the decadal timescale."

North Atlantic

The Atlantic is located at 25°W.

"Excess ¹⁴C in Cariaco Basin sediments indicates a slowing in thermohaline circulation and heat transport to the North Atlantic at that time, and both marine and terrestrial paleoclimate proxy records around the North Atlantic show a short-lived (<400 yr) cold event (Intra-Allerød cold period) that began ca. 13,350 yr B.P."

Ireland

Ireland is located at 53°25'N 8°0'W.

The Allerød occurred during the last interstadial of the Pleistocene: the Woodgrange of Ireland.

Britain

Britain is located at 53°50'N 2°25'W.

The Allerød occurred during the last interstadial of the Pleistocene: the Windermere of Britain.

Western Europe

File:Lommel in northern Belgium, at 12.94 ka, a large late Glacial sand ridge.jpg

Lommel in northern Belgium, near the border with the Netherlands, at 12.94 ka, was a large late Glacial sand ridge covered by open forest at the northern edge of a marsh. Credit: R. B. Firestone, A. West, J. P. Kennett, L. Becker, T. E. Bunch, Z. S. Revay, P. H. Schultz, T. Belgya, D. J. Kennett, J. M. Erlandson, O. J. Dickenson, A. C. Goodyear, R. S. Harris, G. A. Howard, J. B. Kloosterman, P. Lechler, P. A. Mayewski, J. Montgomery, R. Poreda, T. Darrah, S. S. Que Hee, A. R. Smith, A. Stich, W. Topping, J. H. Wittke, and W. S. Wolbach.{{fairuse}}

Soil profile is of a bog in Eberswalde Urstromtal (Agricultural Museum Wandlitz, Brandenburg, Germany). Credit: Anagoria.{{free media}}

"During the Allerød Chronozone, 11,800 to 11,000 years ago, western Europe approached the present day environmental and climatic situation, after having suffered the last glacial maximum some 20,000 to 18,000 years ago. However, the climatic deterioration 11,000 years ago led to nearly fully glacial conditions on this continent for some few hundreds of years during the Younger Dryas. This change is completely out of phase with the Milankovitch (orbital) forcing as this is understood today, and therefore its cause is of major interest."

"During the Allerød a branch of the North Atlantic Current entered the Norwegian Sea (Ruddiman and Mclntyre, 1973, 1981)."

"Recent stratigraphical achievements and long time established chronologies exist for the Late Weichselian, i.e. 10-25 ka BP. During this period Denmark experienced the complex Main-Weichselian glaciation from 25 to about 14 ka BP (Jylland stade, Houmark-Nielsen 1989) followed by the Late Glacial climatic amelioration including the interstadial Bølling-Allerød oscillation (13-11 ka BP), finally leading to the interglacial conditions that characterize the Holocene (Hansen 1965)."

The "large, but so far largely ignored eruption of the Laacher See-volcano, located in present-day western Germany and dated to 12,920 BP, had a dramatic impact on forager demography all along the northern periphery of Late Glacial settlement and precipitated archaeologically visible cultural change. In Southern Scandinavia, these changes took the form of technological simplification, the loss of bow-and-arrow technology, and coincident with these changes, the emergence of the regionally distinct Bromme culture. Groups in north-eastern Europe appear to have responded to the eruption in similar ways, but on the British Isles and in the Thuringian Basin populations contracted or relocated, leaving these areas largely depopulated already before the onset of the Younger Dryas/GS-1 cooling."

"Lommel (1) is in northern Belgium, near the border with the Netherlands. At 12.94 ka (2), this site was a large late Glacial sand ridge covered by open forest at the northern edge of a marsh. More than 50 archaeological sites in this area indicate frequent visits by the late Magdalenians, hunter-gatherers who were contemporaries of the Clovis culture in North America. Throughout the Bölling-Allerod, eolian sediments known as the Coversands blanketed the Lommel area. Then, just before the Younger Dryas began, a thin layer of bleached sand was deposited and, in turn, was covered by the dark layer marked "YDB" above. That stratum is called the Usselo Horizon and is composed of fine to medium quartz sands rich in charcoal. The dark Usselo Horizon is stratigraphically equivalent to the YDB layer and contains a similar assemblage of impact markers (magnetic grains, magnetic microspherules, iridium, charcoal, and glass-like carbon). The magnetic grains have a high concentration of Ir (117 ppb), which is the highest value measured for all sites yet analyzed. On the other hand, YDB bulk sediment analyses reveal Ir values below the detection limit of 0.5 ppb, suggesting that the Ir carrier is in the magnetic grain fraction. The abundant charcoal in this black layer suggests widespread biomass burning. A similar layer of charcoal, found at many other sites in Europe, including the Netherlands (3), Great Britain, France, Germany, Denmark, and Poland (4), also dates to the onset of the Younger Dryas (12.9 ka) and, hence, correlates with the YDB layer in North America."

Usselo is the type site for the 'Usselo Soil', the 'Usselo horizon' or 'Usselo layer', a distinctive and widespread Weichselian (Lateglacial) buried soil, paleosol, found within Lateglacial eolian sediments known as 'cover sands' in the Netherlands, western Germany, and western Denmark; classified as either a weakly podzolized Arenosol or as a weakly podzolized Regosol, where numerous radiocarbon dates, optically stimulated luminescence dates, pollen analyses, and archaeological evidence from a number of locations have been interpreted to show that the Usselo Soil formed as the result of pedogenesis during a period of landscape stability during the Allerød oscillation that locally continued into the Younger Dryas stadial as a marker bed.

The abundant charcoal, which is found in the Usselo Soil, and contemporaneous Lateglacial paleosols and organic sediments across Europe, may have been created by wildfires caused by a large bolide impact, based upon the reported occurrence of alleged extraterrestrial impact indicators and hypothetical correlations with Clovis-age organic beds in North America. However, the contemporaneous nature of the Usselo Soil with Clovis-age organic beds in North America, the presence of impact indicators within it, and the impact origin of the charcoal may only be apparent.

In the second image down on the right, the soil profile is from the "Postdüne" catchment area of ​​the river Finow near Eberswalde (Agrarmuseum Wandlitz, Brandenburg). The upper brown layer is called "Finowboden". During the 700-year period of the Alleröd, 12,500 years ago, the summers were almost as warm as they are today. Pine-birch forests expanded, with their closed vegetation covering the earth's surface. This created one of the first post glacial soils. Until the 1990s, this type of bottoming was known only from Western and Eastern Europe.

Laacher See volcanic eruption

The Laacher See volcano erupted at approximately the same time as the beginning of the Younger Dryas, is a maar lake, a lake within a broad low-relief volcanic crater about 2 km (1.2 mi) diameter in Rhineland-Palatinate, Germany, about 24 km (15 mi) northwest of Koblenz and 37 km (23 mi) south of Bonn, within the Eifel mountain range, and is part of the East Eifel volcanic field within the larger Vulkan Eifel (Vulkaneifel). This eruption was of sufficient size, VEI 6, with over 20 km³ (2.4 cu mi) tephra ejected, to have caused significant temperature change in the Northern Hemisphere.

The timing of the Laacher See Tephra is relative to signs of climate change associate with the Younger Dryas Event within various Central European varved lake deposits. The very large eruption of the Laacher See volcano was at 12,880 years BP, coinciding with the initiation of North Atlantic cooling into the Younger Dryas.

Although the eruption was about twice size as the 1991 Mount Pinatubo eruption, it contained considerably more sulfur, potentially rivalling the climatologically very significant 1815 eruption of Mount Tambora in terms of amount of sulfur introduced into the atmosphere. Evidence exists that an eruption of this magnitude and sulfur content occurring during deglaciation could trigger a long-term positive feedback involving sea ice and oceanic circulation, resulting in a cascade of climate shifts across the North Atlantic and the globe. Further support for this hypothesis appears as a large volcanogenic sulfur spike within Greenland ice, coincident with both the date of the Laacher See eruption and the beginning of cooling into the Younger Dryas as recorded in Greenland. The mid-latitude westerly winds may have tracked sea ice growth southward across the North Atlantic as the cooling became more pronounced, resulting in time transgressive climate shifts across northern Europe and explaining the lag between the Laacher See Tephra and the clearest (wind-derived) evidence for the Younger Dryas in central European lake sediments.

Although the timing of the eruption appears to coincide with the beginning of the Younger Dryas, the amount of sulfur contained would have been enough to result in substantial Northern Hemisphere cooling, evidence exists that a similar feedback following other volcanic eruptions could also have triggered similar long-term cooling events during the last glacial period, the Little Ice Age, and the Holocene in general.

It is possible that the Laacher See eruption was triggered by lithospheric unloading related to the removal of ice during the last deglaciation, a concept that is supported by the observation that three of the largest eruptions within the East Eifel Volcanic Field occurred during deglaciation. Because of this potential relationship to lithospheric unloading, the Laacher See eruption hypothesis suggests that eruptions such as the 12,880 year BP Laacher See eruption are not isolated in time and space, but instead are a fundamental part of deglaciation, thereby also explaining the presence of Younger Dryas-type events during other glacial terminations.

Mount Kilimanjaro

Annotated NASA image of Mount Kilimanjaro indicates its glaciers. Credit: NASA and MONGO.

File:Kibo ice fields.jpg

Shown are the outlines of the Kibo (Kilimanjaro) ice fields in 1912, 1953, 1976, 1989, and 2000, using the OSU aerial photographs taken on 16 February 2000. Credit: Lonnie G. Thompson, Ellen Mosley-Thompson, Mary E. Davis, Keith A. Henderson, Henry H. Brecher, Victor S. Zagorodnov, Tracy A. Mashiotta, Ping-Nan Lin, Vladimir N. Mikhalenko, Douglas R. Hardy, Jürg Beer.

File:Delta 18 Oxygen records Kilimanjaro.jpg

The 10-year average δ¹⁸O records from the (A) NIF2 and (C) NIF3 cores are shown for their entire lengths. (B) NIF2 depths are rescaled to the NIF3 depth scale by matching similar δ¹⁸O features, showing that NIF2 is contemporaneous with the upper 32 m of NIF3. The δ¹⁸O events labeled 1 to 9 are assumed to be coeval. Credit: Lonnie G. Thompson, Ellen Mosley-Thompson, Mary E. Davis, Keith A. Henderson, Henry H. Brecher, Victor S. Zagorodnov, Tracy A. Mashiotta, Ping-Nan Lin, Vladimir N. Mikhalenko, Douglas R. Hardy, Jürg Beer.

File:Decadal averages Kilimanjaro.jpg

The decadal averages of δ 18O from five cores drilled to bedrock are compared. Credit: Lonnie G. Thompson, Ellen Mosley-Thompson, Mary E. Davis, Keith A. Henderson, Henry H. Brecher, Victor S. Zagorodnov, Tracy A. Mashiotta, Ping-Nan Lin, Vladimir N. Mikhalenko, Douglas R. Hardy, Jürg Beer.

Mount Kilimanjaro is located at 3°4'33"S 37°21'12"E.

"Aerial photographs taken on 16 February 2000 allowed production of a recent detailed map of ice cover extent on the summit plateau [diagram at the left]."

"Six ice cores from Kilimanjaro provide an ~11.7-thousand-year record of Holocene climate and environmental variability for eastern equatorial Africa, including three periods of abrupt climate change: ~8.3, ~5.2, and ~4 thousand years ago (ka, [b2k]). The latter is coincident with the “First Dark Age,” the period of the greatest historically recorded drought in tropical Africa. Variable deposition of F^– and Na⁺ during the African Humid Period suggests rapidly fluctuating lake levels between ~11.7 and 4 ka [b2k]."

"The three longest cores (NIF1, NIF2, and NIF3) were drilled to depths of 50.9, 50.8, and 49.0 m, respectively, from the Northern Ice Field (NIF), the largest of the ice bodies. Two shorter cores (SIF1 and SIF2) were drilled to bedrock on the Southern Ice Field (SIF) to depths of 18.5 and 22.3 m, respectively, and a 9.5-m core was drilled to bedrock on the small, thin Furtwa ̈ngler Glacier (FWG) within the crater. Temperatures were measured in each bore-hole; in the NIF, they ranged from –1.2°C at 10 m depth to –0.4°C at bedrock, and in the SIF, they were near 0°C. No evidence of water was observed in the boreholes on the NIF or SIF, but the FWG was water-saturated throughout."

"The chemical and physical analyses, coupled with visible stratigraphy for near-surface layers of the NIF2 core, are shown in [the image at the lower right, A]. Melt features similar to those in the top meter did not occur elsewhere in the NIF or SIF cores. The ongoing down-wasting of the ice fields had not yet removed the ice deposited in the early 1950s, because snow was recovered that contained elevated concentrations of ³⁶Cl from the 1952 Ivy thermonuclear bomb test on Eniwetok Atoll (6). The 1952 time horizon, used for time control in other low-latitude ice cores [the image at the lower right, B], provided a logical origin for development of a depth-age model for the suite of Kilimanjaro cores."

"Water levels in Lake Naivasha, Kenya, [lower diagram at the left,] show higher stands during all three recent solar minima (Maunder, Spörer, and Wolf) with a ~100-year (1670 to 1780 A.D.) period of overflow coincident with the Maunder Minimum. The earliest of the three high stands of Lake Naivasha is ¹⁴C-dated between 1290 and 1370 A.D., and the close association between the water balance in East Africa and solar variability (10) argues for a relationship between the NIF δ ¹⁸O minima and the solar minima [lower diagram at the left]."

The African Humid Period began ~11,000 b2k until 4,000 b2k, "when warmer and wetter conditions prevailed (14, 15) in response to the precession-driven increase in solar radiation (16). During this interval, lakes in the region rose as much as 100 m above present levels (14, 17), and in sub-Saharan Africa lake expansion was massive, with Lake Chad expanding 25-fold from ~17,000 km² to cover an area between ~330,000 and 438,000 km², comparable to that of the Caspian Sea today (14, 18, 19). A paleolake filled the Magadi Natron basin on the border between Tanzania and Kenya to a depth 50 m above the present level and had an area of ~1600 km² in the early Holocene (20)."

"The Kilimanjaro record documents three abrupt climate changes in this region: at ~8.3, ~5.2, and ~4 ka."

These three periods correlate with similar events in the Greenland GRIP and GISP2 cores.

Because glaciers are retreating rapidly worldwide, some important glaciers are now no longer scientifically viable for taking cores, and many more glacier sites will continue to be lost, the "Snows of Mount Kilimanjaro" (Hemingway) for example could be gone by 2015.

South Africa

File:Platinum spikes.jpg

Locations where ~12,800-year-old platinum spikes have been recorded on Earth. Credit: Francis Thackeray/Wits University.{{fairuse}}

The "presence of excessive platinum in sedimentary material extracted from a site in South Africa dating back to [the Pleistocene has been described]. Meteorites are packed with platinum, and an impact with a sufficiently large, disintegrating object would’ve spread platinum across the globe."

The "evidence of a 12,800-year-old platinum spike in Africa is the first to be found on the continent, and it’s yet further evidence in support of the Younger Dryas Impact Hypothesis. According to this theory, either a comet or asteroid struck Earth during the Pleistocene, triggering an impact winter that saw temperatures plummet around the globe. The associated loss of plant life lead to the extinction of many large animal species, along with possible disruptions to human populations around the world."

The "platinum spike [was uncovered] in ancient peat deposits at the Wonderkrater site in South Africa’s Limpopo Province."

The inmage on the right shows the locations "where ~12,800-year-old platinum spikes have been recorded on Earth."

"Our finding at least partially supports the highly controversial Younger Dryas Impact Hypothesis. We seriously need to explore the view that an asteroid impact somewhere on Earth may have caused climate change on a global scale, and contributed to some extent to the process of extinctions of large animals at the end of the Pleistocene, after the last ice age."

The "time of the alleged impact coincides with the disappearance of many animal species around the planet. Africa was no exception, as the Young Dryas period (12,800 to 11,500 years ago) was when several species, including giant buffalos, zebras, and wildebeest, went extinct. At the same time, there’s evidence from this period that human populations might have also suffered. The Clovis people of North America, for example, were suddenly producing fewer stone tools during this period, and a similar drop in stone tool production has been documented among the Robberg culture of southern Africa."

"We cannot be certain, but a cosmic impact could have affected humans as a result of local changes in environment and the availability of food resources, associated with sudden climate change."

The "discovery of ancient pollen at Wonderkrater [...] also dates back to the Young Dryas period. Chemical analysis of this fossilized pollen points to temperature declines, which nicely coincide with a similar cooling period in the Northern Hemisphere."

The result is important "because it suggests that the Younger Dryas impact event had global effects. Previously, [it was known] that it affected nearly all of the Northern Hemisphere, but not the South. Then, recently, another study was published showing a platinum peak at Pilauco, Chile, indicating that South America was affected. Now, we know that southern Africa was affected as well, nearly 8,000 kilometers [5,000 miles] away from the nearest similar site in Syria, making this a global event."

The "Younger Dryas Impact Hypothesis is a highly controversial idea, given the lack of evidence. Critics have said an “an age discrepancy” exists between different sites where proposed impact markers have been found, and that much of the evidence, such as magnetic microspherules, nanodiamonds, shocked quartz, and other minerals, are ambiguous in nature and open to interpretation. It also doesn’t help that an associated impact crater hasn’t been linked to the supposed event."

A "fascinating discovery from 2018 revealed the presence of a hidden impact crater beneath the Hiawatha Glacier in Greenland. This crater measures around 31 kilometers (19 miles) wide, and it struck the Earth at some point between 3 million and 12,000 years ago. This could very well be the impact crater from the Young Dryas event, but more evidence is needed."

"It is correct that the crater is not well dated, but there’s good evidence that it is geologically young, that is, it formed within the last 2 to 3 million years, and most likely it is as young as the last Ice Age [which ended around 12,000 years ago]. We are currently trying to come up with ideas on how to date the impact. One idea is to drill through the ice and get bedrock samples that can be used for numerical dating."

This crater "might possibly have been the very place where a large meteorite struck the planet Earth 12,800 years ago, and that a meteorite of this size would have mostly certainly resulted in "global consequences"."

Egypt

File:Neolithic skull Allerod Egypt1.JPG

Neolithic skull is from the mysterious people that enabled the rise of ancient Egypt. Credit: Joel D. Irish, Jacek Kabacinski, and Czekaj-Zastawny Agnieszka.{{fairuse}}

File:Well preserved vs. wind‐eroded remains at Gebel Ramlah.jpg

Well preserved vs. wind‐eroded remains are at Gebel Ramlah. Credit: Joel D. Irish, Jacek Kabacinski, and Czekaj-Zastawny Agnieszka.{{fairuse}}

File:Extension of Gebel Ramlah paleo-lake and location of Neolithic cemeteries.png

Drawing shows extension of Gebel Ramlah paleo-lake and location of Neolithic cemeteries. Credit: Jacek Kabaciński.{{fairuse}}

File:Grave artefacts from 2001-2003 excavations.jpg

Grave artefacts from 2001-2003 excavations are a "Tulip" beaker (upper left), grey diorite bowl (upper right), stone point and Celt (lower left) and carved/drilled mica. Credit: Joel D. Irish, Jacek Kabacinski, and Czekaj-Zastawny Agnieszka.{{fairuse}}

Egypt is located at 26°N 30°E.

The "Allerød Chronozone, 11,800 to 11,000 years ago".

"In the Egyptian Western Desert, the beginnings of human occupation date as early as ca. 9300 BC."

"In the Egyptian Western Desert, part of the Eastern Sahara, the advent of the first humid interphase is dated to ca. 9300 BC and correlates with the first appearance of Neolithic humans there (Schild and Wendorf 2013). Neolithic pastoralists were then continuously present in this area for almost 6000 years, not departing until the middle of the third millennium BC (Applegate and Zedeño 2001)."

"[Before the pharaohs and pyramids of the Dynastic period starting about 3,100 BC], about 9,300-4,000 BC, enigmatic Neolithic peoples flourished. [It] was the lifestyles and cultural innovations of these peoples that provided the very foundation for the advanced civilisations to come."

"Along with fast and radical climatic changes in the Northern Hemisphere at the end of the Late Glacial and beginning of the Holocene, ca. 9550 BC (Alley et al. 1993; Lowe et al. 2008), the first signs of climatic improvement are readable in the early Preboreal period of the Sahara (Kuper and Kropelin 2006). In the Egyptian Western Desert, part of the Eastern Sahara, the advent of the first humid interphase is dated to ca. 9300 BC and correlates with the first appearance of Neolithic humans there (Schild and Wendorf 2013). Neolithic pastoralists were then continuously present in this area for almost 6000 years, not departing until the middle of the third millennium BC (Applegate and Zedeño 2001)."

Settlements "along the shores of temporary paleo-lakes (or playa) of the Nabta-Kiseiba region, within frameworks of chronostratigraphic units and correlated with major climatic fluctuations [four] occupation periods were defined: Early (ca. 9300–6150 BC), Middle (ca. 6050–5550 BC), Late (ca. 5500–4650 BC), and Final Neolithic (ca. 4600–3600 BC), each separated by dry periods manifested by remarkable eolian sedimentation and erosion."

"In 2009, a few hundred meters from the Gebel Ramlah paleo-lake shore, [...] one of the most unique Neolithic burial complexes known in northeastern Africa and beyond [was discovered]. It included a cemetery for the burial of infants, which was placed next to a much larger cemetery for older children, juveniles, and adults. Both areas date to the Final Neolithic period (site E-09-02). Single graves and small aggregations of graves from different Neolithic phases were also found in the vicinity. Other cemeteries and single burials were located as well nearby [...]. Together, they form an exceptional interment area that was used for millennia by Neolithic herders."

"Gebel Ramlah is a pronounced, rocky massif on the landscape [see the third image down on the right] that rises approximately 100 m above the surrounding desert floor [...]. To the south, a lake existed during the early and middle Holocene that would have measured some 2.5 km long by 0.6 km wide [...]. Morphology of the shore zone, modified by erosion and deflation, is diversified. Northern shores, located near the steep southern slopes of the Gebel, are morphologically uniform with clearly visible lake terraces, cut by short stream channels (wadi) draining waters from the Gebel to the lake. The more diversified landscape of the southern and western shores is dominated by large and wide river channels with numerous smaller tributaries that delivered waters from a vast catchment area to the lake. Hillocks and large peninsulas between the channels and gentle slopes are typical. They are significantly more extensive in size than those on the northern shore. Lastly, the eastern edges of the lake are mostly covered by sand dunes but, where observation is possible, the banks’ slopes appear to be gentle."

"During the course of survey, evidence of a diverse human occupation was recorded including large, long-term settlements, small occupations, short-lived camps, and traces of penetrations. In a chronological/cultural perspective, the earliest evidence of human presence dates to the Early Neolithic (El Adam and El Ghorab units) and the most intensive occupation developed during the climatic optimum of the Holocene (El Jerar unit), followed by more sparse Middle, Late, and Final Neolithic settlements (Czekaj-Zastawny et al. 2017)."

"A concentration of six cemeteries, grave clusters, and single burials comprising the most unusual mortuary grounds of Neolithic pastoralists recorded in the Western Desert, were discovered and excavated. The earliest evidence of mortuary practices, in the form of single separate burials, is radiocarbon-dated to the second half of the Early Neolithic (ca. 6500 BC), followed by Middle and Late Neolithic burials. Only later, at the advent of the Final Neolithic (ca. 4500 BC), were actual cemeteries were established."

"In 2001-2003 we excavated three cemeteries from this era – the first in the western desert – where we uncovered and studied 68 skeletons. The graves were full of artefacts, with ornamental pottery, sea shells, stone and ostrich eggshell jewellery [see last image on the right]. We also discovered carved mica (a silicate mineral) and animal remains, as well as elaborate cosmetic tools for women and stone weapons for men."

Northern Asia

"Kamminga and Wright (1988), Wright (1995) and Neves and Pucciarelli (1998) have demonstrated, however, that the Zhoukoudian Upper Cave (UC) cranium 101 display marked similarities with Australo-Melanesians. Cunningham and Wescott (2002) has shown that although highly variable, none of the three specimens from this site (UC 101, UC 102, UC 103) resembles modern Asian populations. Matsumura and Zuraina (1999:333) reported the presence of the “Australo-Melanesian lineage” in Malaysia as late as the terminal Pleistocene. If we consider that UC is dated to between 32,000 BP and 11,000 BP, the fixation of the classical Mongoloid morphology in North Asia could have been a recent phenomenon (terminal Pleistocene/early Holocene), a hypoth- esis favored by several authors (see Cunningham and Wescott, 2002 for a review)."

"Accordingly, an Australo-Melanesian-like population present in North Asia by the end of the Pleistocene could have been the source of the first Americans. This would explain the presence of a non-Mongoloid morphology in the New World without invoking a direct transpacific route departing from Australia, as suggested by Rivet (1943)."

"Lahr (1995) has argued that human diversity in northern Asia was probably higher in the final moments of the Pleistocene than today, at least as far as cranial morphology is concerned. Therefore, non-Mongoloid Asians could have arrived in the Americas using the Behring Strait as the gate of entry following either the shore of Beringia or a land bridge."

See also

• Classical planets (Hasselo stadial) (109 kB)
• Dates (Hadean) (173 kB)
• Hominins (Miocene) (25 kB)
• Human DNA (Paleogene) (168 kB)
• Ice cores (Calabrian) (100 kB)
• Middle Ages (-10th century) (108 kB)
• Paleanthropology (Paleogene) (195 kB)
• Sciences (-55th Century) (101 kB)
• Rocks