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The Usselo Soil and the Younger Dryas Extraterrestrial Impact Hypothesis
A new paper, which is in press in âBoreasâ, about the
Usselo Soil and the Younger Dryas extraterrestrial impact
hypothesis, has recently appeared. It is:
Kaiser, K. H., A., N. Schlaak, M. Jankowski, M, P. Kuhn,
S. Bussemer, and K. Przegietka, in press, Palaeopedological
marker horizons in northern central Europe: characteristics
of Lateglacial Usselo and Finow soils. Boreas.
Doi: 10.1111/j.1502-3885.2008.00076.x. ISSN 0300-9483
One important point that this paper makes is that what
has been called either the âUsselo Horizonâ or âUsselo
Layerâ is not a "layer" in terms of being a tabular
depositional body of either rock or unconsolidated sediment
created separately from the sediments above and below it.
Rather, it is a relict, buried Albic Arenosol and Brunic
Arenosol (paleosol) that developed in preexisting sediment
as the result of a period of surface weathering during a
period of nondeposition. As a paleosol, it is pedolostratigraphic
marker horizon, not a depositional horizon as some
proponents of the Younger Dryas extraterrestrial impact
hypothesis imply by the use of the term âhorizonâ.
Another important points this paper makes is that like
any paleosol, the Usselo Soil and its correlative Finow
Soil are time-transgressive in terms of when their burial
ended the period of weathering and soil formation that
created these paleosols. Radiocarbon dates from the
Usselo Soil represent all of the Allerod and Younger
Dryas age with a few outlier dates of Preboreal age. Thus,
both paleosols represent a variable period of nondeposition
encompassing either only the Allerod age or the Allerod
and Younger Dryas ages depending on specific location
at which it is examined. Thus, the Osselo Soil cannot be
a single event bed created during a single instantaneous
event. Instead, it is a paleosol that reflects nondeposition
over a variable period of time that varies between 1,000
and 1,500 years in length.
This paper a
of eolian sand overlying the
Usselo Soil. These OSL dates demonstrate that within
some parts of the area, in which the Usselo Soil occurs, it
was initially buried by eolian sands of late Allerod age.
Thus, at several locations, the Usselo Soil predates the
Allerod-Younger Dryas boundary and it is impossible for
the Usselo Soil at several locations be to connected with
any Allerod-Younger Dryas boundary event of any type.
Some other papers about the Usselo Soil (Usselo Layer /
Bertran, P., G. Ge. Allenet, T., F. Naughton, P. Poirier, M. F.
and Goni, 2009. Coversand and Pleistocene palaeosols
in the Landes region, southwestern France. Journal of
Quaternary Science. no. 3, vol. 24 pp. 259â269.
Derese, C. D. Vandenberghe, E. Paulissen, P. V. den Haute, in
press, Revisiting a type locality for Late Glacial aeolian sand
deposition in NW Europe: Optical dating of the dune complex
at Opgrimbie (NE Belgium). Geomorphology.
Hoek, W. Z., 1997, Paleogeography of Lateglacial vegetations:
Aspects of Lateglacial and Early Holocene vegetation, abiotic
landscape, and climate in The Netherland. Ook verschenen als
handelsed.: Utrecht: Koninklijk Nederlands Aardrijkskundig
Genootschap (Nederlandse Geografische Studies,
ISSN 0169-4839 ; 230) Proefschrift Vrije Universiteit
Hoek, W. Z., and S. J. P. Bohncke, 2002, Climatic and
environmental events over the Last Termination, as recorded
in The Netherlands: a review. Netherlands Journal of
Geosciences (Geologie en Mijnbouw) vol. 81, no. 1, pp. 123-137
Kasse, C., 1997, Cold-Climate Aeolian Sand-Sheet Formation
in North-Western Europe (c. 14Â12.4 ka); a Res
radation and Increased Aridity. Permafrost and
Periglacial Processes. vol. 8, pp. 295-311.
Kasse, C., 2002, Sandy aeolian deposits and environments
and their relation to climate during the Last Glacial Maximum
and Lateglacial in northwest and central Europe. Progress in
Physical Geography. vol. 26, no. 4, pp. 507-532.
Kasse, C., D. Vandenberghe, F. De Corte, and P. Van den
Haute, 2007, Late Weichselian fluvio-aeolian sands and
coversands of the type locality Grubbenvorst (southern
Netherlands): sedimentary environments, climate record and
age. Journal of Quaternary Science. vol. 22, pp. 695â708.
van der Hammen, T., and B. van Geel, 2008, Charcoal in
soils of the AllerÃd-Younger Dryas transition were the
result of natural fires and not necessarily the effect of
an extra-terrestrial impact. Netherlands Journal of
Geosciences. vol. 8. no. 4, pp. 359-361
Paul V. Heinrich
Baton Rouge, Louisiana