Younger Dryas Comet 12,900 BP

Deep troughs in Lake Superior support the hypothesis of Younger Dryas Boundary (YDB) comet impact 12,900 BP. The impact theory explains the megafauna extinction, a black mat across the Northern hemisphere, nanodiamonds, platinum and iridium, and the enigmatic Carolina Bays (CB). While the CB were thought to predate Clovis cultural remains, but this must now be seen as spurious as the CB occur on Long Island, an LGM terminal moraine & on endglacial flood plains, according to Allen West. The CB sand rims are exceptionally pure quartz with large phenocrysts, and also they exude hydrogen (H). This suggests origin from deep granitic plutons, the granite typically being oversaturated with silica. When the Russian Kola Peninsula Superdeep Borehole had reached 40,000 ft, H was boiling from the borehole. This H is among volatiles copiously dissolved in the mantle, from the primitive solar nebula. The granite is from the Lake Superior Province. Lakes Superior, Michigan, Huron & Ontario have deep holes, reaching to below sea level. Bathymetry exhibits a ~145 km circular contour in Eastern L. Superior, where deep troughs occur, eroded in breccias infilling impact explosion cavities many kms deep, as much as 15 to 35 km, the comet fragments coming in from the NW, with the holes lined up along the trajectory. This was an oblique impact with an extremely low angle of incidence, so the ejected granite quartz sands ended up in the CB along the Eastern seaboard principally.


Introduction
During the last decade, the late Ice Age cooling event 12,900 yrs ago at the Younger Dryas boundary (YDB), with re-advance of continental ice sheets and megafauna extinction (incl. mammoth), has received prominent scientific attention, due to a series of publications by Richard Firestone, Lawrence Berkeley Nat. Lab., and his team of colleagues, claiming the discovery of a cosmic object impact that caused the YDB event [1] [2]. There still is ongoing scientific debate & controversy followed by many people with great interest.
The public likewise may be greatly interested, I believe. Since the occasion of the Chelyabinsk meteorite fall that occurred on Feb. 15, 2013, many have been paying attention to cosmic object impacts threatening civilization, regardless of political ideology. This leads me to believe the readership of this journal may carry an inherent interest in such matters, linking outer space to our little, usually solitary planet. This is why I am motivated to comment on the YDB cosmic impact hypothesis of Richard Firestone & his team: in the last few months and weeks, I have been very fortunate to learn several key aspects of the YDB events, in part by email exchange with some of the principals who graciously have answered my questions, and helped me to arrive at the new scenario presented in this paper, which I hope will remove any doubts about the YDB comet hypothesis. Special thanks are due for valuable information provided by my friends Allen West and Tim Harris. Final clue came from a science poster by Prof. Robert S. Regis and colleagues, N Michigan University, Marquette, MI [3].

Review of Known Facts & Logical Process of Inferences
The image emerges of an enormous event to hit the continent of N America 12,900 BP, and to a lesser extent throughout large parts of Eurasia. Next, let us list the facts from a variety of sources that are known, & thereupon enter into an orderly process of logical deduction & inference to arrive at our results. So then, here are the reasons and this is what we should believe that it happened.

Mysterious Carolina Bays Challenge
The cosmic object impact theory explains the megafauna extinction, a black mat across the Northern hemisphere, nanodiamonds, platinum and iridium, & much, much more, in particular the enigmatic Carolina Bays (CB) predominantly found on the Eastern seaboard, elliptical ovals all oriented in a NW to SE direction ( Figure 1). Bays are surrounded by rims composed of sand. These sometimes

Dating the Carolina Bays
The CB were thought to predate the Clovis cultural remains, but this must now be seen as spurious, as the CB occur on Long Island, a Last Glacial Maximum (LGM) terminal moraine & on end-glacial flood plains, according to Allen West, personal communication.

Granitic Origin of CB Quartz Sands
The CB sand rims are exceptionally pure quartz with large phenocrysts, and also they ooze hydrogen (H) [4]. This suggests origin from deep granitic plutons, the granite typically being oversaturated with silica.

Lake Superior Granite Province
A possible source of granite is in the Lake Superior province, rich in ancient granite, which typically arises as plutons erupted from the Mohorovicic (Moho) discontinuity.

Unusually Deep Holes in Great Lakes and Impact Cratering Hypotheses
There are deep holes in four of the Great Lakes, Superior, Michigan, Huron & Ontario, reaching to below sea level. No plausible mechanism of erosive glacial action can explain these. This has long been noted by the Firestone team as indicative of impact cratering. However, their main thesis was that aerial bursts of a comet occurred with fragments causing minor cratering in the Lakes (Figure 2).
Geologist Robert Dietz, famous for discovering Sudbury, ON, as an astrobleme (from the nickel and other platinum group metal speckles in the rocks around the structure), also long ago already had contributed the conjecture that Lake Superior is an impact crater. 1

Carolina Bays Ejecta from YDB Comet
The ejection of quartz sands toward the Atlantic East Coast would now seem to

Multiple Comet Fragment Impacts
The holes appear to lie on or near a straight NW-SE line. Comets are notoriously fragile so an incoming missile is liable to break up under "impact focusing," a kind of tidal force effect (recall 1994 when Comet SL9 broke into 23 pieces which later fell into planet Jupiter). This explains the four holes. Even Lake Erie appears to have been impacted, perhaps by a lesser fragment. There are numerous examples on Earth and other solar system bodies of crater alignments, as the separate frags are likely to impact near the projection of the approach trajectory.

Deep Excavation of Granites by Impact Explosions
Here, we claim excavation several km deep by comet fragments, the initial impact explosions perhaps reaching to near the Moho and ejecting quartz sands typically including phenocrysts and infused with H seeping up from the mantle.

Large 145 km Diameter Crater in Lake Superior
A circular contour of about 145 km diameter appears in Eastern Lake Superior bathymetry (Figure 3). Deep cavities, ~1/10 to 1/4 of crater diameter deep are thought to be created initially by the impact explosion. For the L. Superior circular hole, this amounts to a cavity 15 to 35 km deep. This could be a complex multiring crater, with an outer wall of 145 km and an inner rim of 100 km. Smaller craters appear N and E, with partial overlap of contour lines.

Initial Cavity Collapse
Breccia almost immediately would have refilled collapsing initial cavities.

Unusual 200 m Deep Trenches in Deep Holes
The deep holes show scars in the form of valleys, channels or troughs. The maximally 200 m deep troughs or trenches show up clearly in satellite maps ( Figure   4(a)). The above cited poster of Prof. Regis & colleagues at N Michigan University [3] provides detailed data for the troughs or trenches & geological insights lucidly explained. The following verbatim quotes are from this poster: "… unusually deep bedrock troughs in the eastern basin of Lake Superior," stating that these "trenches were formed by south-flowing subglacial streams… Our preliminary conclusion is that these trenches represent the normal drainage that develops near the margins of an ice lobe when is rests on erodible rock." The area described is coincident precisely with the 145 km circular contour seen in the bathymetry.

Trenches Are Evidence for Breccia in Lake Bottoms
Here, it is our hypothesis that the trenches are atop impact craters, typically filled

Conclusions
Before The fact that Yellowstone is impact caused [5] relegates this argument to the dustbin of science history.