"...have allowed us to interpret the 4kyr BP dust-event as the fallout of a distal impact-ejecta rather than a sudden drought.
I ran across this recently, and wondered if there is any archaeological, historical/biblical, or anectodal records of dramatic changes in the time following this impact event.
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*
....still studying soils and their (recently recognized) strong influence upon climate;
...but impact events affect climate too....
*New Trends in Soil Micromorphology
Kapur, S., Mermut, A. R., Stoops, Georges
Published: 2008
LC Call Number: S593.2 /.N48 /2008
Hardcover, ISBN 978-3-540-79133-1
"...have allowed us to interpret the 4kyr BP dust-event as the fallout of a distal impact-ejecta rather than a sudden drought.
"...link the fallout of the far-traveled dust with high temperature effects at the soil surface and violent deflation of surface horizons by high speed winds."
"Results are based on soil data from the Eastern Khabur basin (North-East Syria), the Vera Basin (Spain), and the lower Moche Valley (West Peru) compared with a new study at the reference site of Ebeon (West France)."
"In the four regions studied, the intact 4kyr BP signal is identified as a discontinuous burnt soil surface with an exotic dust assemblage assigned to the distal fallout of an impact-ejecta."
"Studies showed how a high quality signal allows [science] to discriminate the short-term severe landscape disturbances linked to the exceptional 4 kyr BP dust event from more gradual environmental changes triggered by climate shift at the same time."
http://espace.library.curtin.edu.au/R/?func=dbin-jump-full&object_id=118212&local_base=GEN01-ERA02
The co-occurrence of a sharp dust peak, low lake levels, forest reduction, and ice retreat at ca. 4-kyr BP throughout tropical Africa and West Asia have been widely explained as the effect of an abrupt climate change. The detailed study of soils and archaeological records provided evidence to re-interpret the 4 kyr BP dust event linked rather to the fallback of an impact-ejecta, but not climate change. Here we aim to further investigate the exceptional perturbation of the soil-landscapes widely initiated by the 4 kyr BP dust event. Results are based on soil data from the eastern Khabur basin (North-East Syria), the Vera Basin (Spain), and the lower Moche Valley (West Peru) compared with a new study at the reference site of Ebeon (West France). The quality of the 4 kyr BP dust signal and the related environmental records are investigated through a micromorphological study of pedo-sedimentary micro-fabrics combined with SEM-microprobe, mineralogical, and geochemical analyses.
In the four regions studied, the intact 4 kyr BP signal is identified as a discontinuous burnt soil surface with an exotic dust assemblage assigned to the distal fallout of an impact-ejecta. Its unusual two-fold micro-facies is interpreted as (1) flash heating due to pulverization of the hot ejecta cloud at the soil surface, and (2) high energy deflation caused by the impact-related air blast. Disruption of the soil surface is shown to have been rapidly followed by a major de-stabilisation of the soil cover. Local factors and regional settings have exerted a major control on the timing, duration, and magnitude of landscape disturbances. Studies showed how a high quality signal allows to discriminate the short-term severe landscape disturbances linked to the exceptional 4 kyr BP dust event from more gradual environmental changes triggered by climate shift at the same time.
just fyi....
http://www.springer.com/earth+sciences+and+geography/earth+system+sciences/book/978-3-540-79133-1
The book contains state of the art new research results in micromorphology as well as other disciplines of soil science. It provides very useful up-to-date information for researchers, educators, graduate students interested in microscopic and submicroscopic studies of soils and sediments. In the past, micromorphology has been considered almost solely as a descriptive and interpretative branch of science. Attempts are now made to obtain quantitative data. There has been much progress in applying soil micromorphology in Quaternary geology, in particular identifying and characterizing palaeosols. The new areas for soil micromorphology are soil ecology, materials sciences and archaeology.
There is lots of literature about shifting civilizations, as well as the climate shifting, at ~4000 BP.
Googled: trend in climate "4,000 years BP"
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This could help explain observations in both climate history and anthropology.
http://www.stanford.edu/~meehan/donnellyr/3000bc.html
4000 BC: Global; Holocene delta development worldwide
Holocene delta development worldwide transgressive sequence of deltaic deposits
4000 BC: Mesopotamia; Mesopotamia delta Stratigraphic relations by the author showing the rapid development of a rich, fertile delta in Mesopotamia
...also
http://hol.sagepub.c.../1/117.abstract
"Our results show that this aridification trend began around 8000 yr BP, and culminated around 4000 yr BP."
...and
http://www.sciencedi...033589499921087
Title:
"Age-constrained pollen data and magnetic susceptibility of an alpine peat profile from the Garhwal Higher Himalaya display a continuous record of climate and monsoon trends for the past 7800 yr."
About 7800 cal yr B.P., dominance of evergreen oak (Quercus semecarpifolia), alder (Alnus), and grasses in the pollen record reflect a cold, wet climate with moderate monsoon precipitation. From 7800 to 5000 cal yr B.P., vegetation was progressively dominated by conifers, indicating ameliorated climate with a stronger monsoon. A warm, humid climate, with highest monsoon intensity, from 6000–4500 cal yr B.P. represents the mid-Holocene climatic optimum. Between 4000 and 3500 cal yr B.P., the abundance of conifers sharply decreased, with the greatest increase in evergreen oak. This trend suggests progressive cooling, with a decrease in the monsoon to its minimum about 3500 cal yr B.P. Two relatively minor cold/dry events at ca. 3000 and 2000 cal yr B.P. marked step-wise strengthening of the monsoon until ca. 1000 cal yr B.P. After a cold/dry episode that culminated ca. 800 cal yr B.P., the monsoon again strengthened and continued until today.
A sharp decrease in temperature and rainfall at 4000–3500 cal yr B.P. represents the weakest monsoon event of the Holocene record. This cold/dry event correlates with proxy data from other localities of the Indian subcontinent, Arabian Sea, and western Tibet.
===http://books.google.com/books?id=ZWNtHLz3fXYC&pg=PA99&lpg=PA99&dq=trend+in+climate+%224,000+years+BP%22&source=bl&ots=mpQkp1Wjjg&sig=9vlxFibLEQOmGaBJynfs1dKneX8&hl=en#
"Forest Ecosystems" By David A. Perry
"In the eastern North America.... A very warm and dry period from 8000 to 4000 years BP produced major changes in vegetation patterns.... The cooling trend that began approximately 4000 years BP readjusted these boundaries to roughly those we see today.
Similar changes occurred in western North America."
"A major warming trend beginning around 8000 BP was accompanied by both the appearance of Douglas-fir and an increase in fire frequency. With the return to a cooler, moister climate around 4000 BP, fire frequency declined and community composition shifted to western hemlock/red cedar/Douglas-fir, a forest type that persists today."
From Peru to Syria, "...the intact 4kyr BP signal is identified as ...the distal fallout of an impact-ejecta."
Wow!
I'd appreciate any links that highlight what civilizations (or agriculture/mining) were doing around that time, which might be related to any effects from an impact event--such as these high temperature effects at the soil surface and violent deflation of surface horizons by high speed winds."
~
