It looks like you're using an Ad Blocker.
Please white-list or disable AboveTopSecret.com in your ad-blocking tool.
Some features of ATS will be disabled while you continue to use an ad-blocker.
The cold period known as the Younger Dryas (YD)
climate oscillation occurred between c. 12.9 ka
BP and c. 11.7 ka BP (e.g. Berger 1990; Peteet
1995; Bj¨orck 2007; Lowe et al. 2008). This sudden
climate change is generally thought to result from
an abrupt change of atmospheric and oceanic
circulations (e.g. Teller et al. 2002; McManus
et al. 2004; Brauer et al. 2008). The beginning
of the YD in North America can at times be
stratigraphically marked by the so-called black mat,
a thin dark layer of organic-rich material (e.g.
Firestone et al. 2007; Haynes 2007, 2008; Pigati
et al. 2009, 2012). The black mat, however, is a
general term that includes, in addition to the dark
organic-rich deposits, some marls and diatomites
that are light grey in color (e.g. Ballenger et al.
2011). A lot of attention was lately paid to the
black mat because of a widespread discussion on
the possibility of the extraterrestrial impact shortly
before the onset of the YD climate oscillation
(e.g. Firestone et al. 2007; Haynes et al. 2010;
Pigati et al. 2009, 2012; Andronikov et al. 2011,
2014; Fayek et al. 2012; Kennett et al. 2015).
There are reports about findings of unusual objects
such as carbon spherules, nanodiamonds, glasslike
carbon, melt-glass, as well as enhanced
amounts of platinum group elements in sediments
corresponding to the lower YD boundary (LYDB) in
support of the hypothesis (e.g. Firestone et al. 2007;
Kennett et al. 2009; Mahaney et al. 2010, 2013;
Bunch et al. 2012; Petaev et al. 2013; Wu et al.
© 2016 Swedish Society for Anthropology and Geography 1
DOI:10.1111/geoa.121222013). One such characteristic object reported is
magnetic microspherules (e.g. Firestone et al. 2007;
Israde-Alc´antara et al. 2012; LeCompte et al. 2012;
Wittke et al. 2013).
Strongly elevated concentrations of the magnetic
microspherules in a thin sandy layer corresponding
to the LYDB are revealed for the BWD-1
sedimentary sequence. Sharp increase of the
number of microspherules in sediments located
along the LYDB is in agreement with observations
made by Firestone et al. (2007, 2010) and
LeCompte et al. (2012). Because overall close
chemical, mineralogical, and structural similarity
of the BWD-1 hollow microspherules to those
directly related to known meteorite occurrences
and/or meteoritic events, the cosmic origin of the
former seems to be a credible hypothesis. If we
accept such origin of the BWD-1 microspherules,
then ablation of iron or stony meteorites during their
passage through the Earth’s atmosphere seems to be
the most plausible mechanism for their formation.
However, the exact mechanism of the formation
of the magnetic microspherules is not completely
clear. In addition to the formation during ablation
of the meteoritic body in the Earth’s atmosphere
(as in the case of the microspherules studied), they
could be produced during the airburst of such a
body, or could result from the impact of the ET
body. When meteorite influx increases, it results,
in particular, in elevated concentration of the
hollow magnetic microspherules in discrete layers
of terrestrial sediments. The elevated concentration
of microspherules of the BWD-1 type is a
known phenomenon for multiple LYDB locales
across North America (e.g. Firestone et al. 2007;
LeCompte et al. 2012; Pigati et al. 2012; Wittke
et al. 2013). The presence of the high number of
such microspherules in the sediments can serve
as a local stratigraphic marker in identification
of the LYDB there where dark variety of the
black mat is absent. If one applies methods of
microstratigraphy to paleosols of the suggested
(LYDB) age, the strongly elevated concentrations
of magnetic microspherules would mark precisely
the time of around 12.9 ka BP. The data from
the present study along with observations made
on sediments around the LYDB elsewhere suggest
that some unusual event took place just before the
onset of the YD climate oscillation. However, an
understanding of what happened at c. 12.9 ka BP
and how it is related (if at all) to the onset of the
YD climate oscillation requires further search.
that is in fact blatantly untrue.
No skeletal remains of horse, camel, mammoth, mastodon, dire wolf, American lion, short-faced bear, sloth, tapir, etc:, or Clovis artifacts have ever been found in situ within the YD age black mat,
and what bearing does that have on the question.
and no post-Clovis Paleoindian artifacts have ever been found in situ stratigraphically below it.
originally posted by: punkinworks10
The skeptics are cherry picking the data every bit as bad as the stichinites and all their ilk do.
The Younger Dryas boundary (YDB) cosmic-impact hypothesis is based on considerable evidence that Earth collided
with fragments of a disintegrating ≥100-km-diameter comet, the remnants of which persist within the inner solar
system ∼12,800 y later. Evidence suggests that theYDB cosmic impact triggered an “impact winter” and the subsequent
Younger Dryas (YD) climate episode, biomass burning, late Pleistocene megafaunal extinctions, and human cultural
shifts and population declines. The cosmic impact deposited anomalously high concentrations of platinum over much
of theNorthernHemisphere, as recorded at 26YDB sites at theYDonset, including theGreenland Ice Sheet Project 2 ice
core, in which platinum deposition spans ∼21 y (∼12,836–12,815 cal BP). The YD onset also exhibits increased dust
concentrations, synchronous with the onset of a remarkably high peak in ammonium, a biomass-burning aerosol. In
four ice-core sequences fromGreenland, Antarctica, and Russia, similar anomalous peaks in other combustion aerosols
occur, including nitrate, oxalate, acetate, and formate, reflecting one of the largest biomass-burning episodes in more
than 120,000 y. In support of widespread wildfires, the perturbations in CO2 records from Taylor Glacier, Antarctica,
suggest that biomass burning at the YD onset may have consumed ∼10 million km2, or ∼9% of Earth’s terrestrial biomass.
The ice record is consistentwith YDB impact theory that extensive impact-related biomass burning triggered the
abrupt onset of an impact winter, which led, through climatic feedbacks, to the anomalous YD climate episode.
Detailed microscopic investigations of horizons in a surface paleosol, part of a pedostratigraphic stack of tills at New Mountain, Antarctica, dated to the middle Miocene climatic optimum event (ca. 15 Ma), suggest not only that the paleoclimate history of the continent can be read from stratigraphic layers within paleosols but also that records of cosmic events may lie embedded in coatings on sand clasts resident in paleosols.
The projected link to the probable black-mat event of 12.8 ka is reinforced by the presence of fresh opaque carbon and other cosmic signatures on grain surfaces that overlie well-weathered grain features, presumably weathering from middle Miocene time near today. Evidence of CO2 and NOx accumulations dated to 12.9 ka in the Taylor Ice Dome suggest that the black-mat impact/airburst of the same time line as the Younger Dryas boundary may have reached across South America and the Pacific Ocean to the Dry Valley Mountains of Antarctica.
originally posted by: peter vlar
a reply to: punkinworks10
As much as I've been a holdout on this and for as long as I have, it's getting very difficult to argue away the mounting data supporting the YD Impact hypothesis. Were definitely closing in on that gap separating hypothesis from theory. I'll take a peek through this tomorrow when. I've got a little more time to give it the proper attention.
I've been a little preoccupied keeping up with John Hawks archaic hominid genetic analysis which is in and of itself, rewriting what we thought we knew about Pleistocene hominids from H. Naledi in the extreme South to Denisovan and Neanderthal ties in the north as well as recent data showing that East Asians actually have more Neanderthal Y DNA than Europeans. Sima de Los Huesos has completely changed everything we though we knew. If my youngest was a little older, I would be doing everything I could to involve myself in those studies or at the very least try to sneak a foot in at Max Planck and get my fingers into some of the work Svante Paabo is doing there.
The last 20 years of Paleoanthropology have given us more dats than the first century and a half of Anthropology as a whole. It's a pretty exciting time for dorks like me who get excited about what would make most people fall asleep. In other words... Keep it coming. You've definitely got your finger on the pulse of the YD Impact hypothesis and I'm very interested to see where it eventually leads to.
ABSTRACT: This study investigates changes in climate, vegetation, wildfire and human activity in
Southwest Asia during the transition to Neolithic agriculture between ca. 16 and ca. 9 ka. In order to
trace the fire history of this region, we use microscopic charcoal from lake sediment sequences, and
present two new records: one from south central Turkey (Akgo¨ l) and the other from the southern Levant
(Hula). These are interpreted primarily as the result of regional-scale fire events, with the exception of a
single large event ca. 13 ka at Akgo¨ l, which phytolith analysis shows was the result of burning of the
local marsh vegetation.