🚀 go-pugleaf

<snip>
"Val Lentz" <vlentz@shaw.ca> wrote in message news:<ozzfc.129780$Ig.92682@pd7tw2no>...

> I am not knowledgable about North America at all, so this little report from
> 2000 is probably old hat...  But apparently not every thing gets chewed up
> by those glaciers:
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Val:
  I've reviewed my notes and maps on the area, which can be seen in Fig. 1, here:

http://alms.biology.ualberta.ca/DwnldDocs/LakeWatchRpts/Buck%2001.pdf

  The Chabots are on the east side of the lake,
between the lake and the hook-shaped access road
(directly above the word "SCALE", and left of "To Winfield").

  The site's geomorphology is 'way too complicated to easily explain,
and I must admit to frustration in trying to do so.
  Please bear with me, and I hope that what you see below isn't
too boring to follow.

  Buck Lake probably started out as a subglacial meltwater channel,
near the margin of the Laurentide Ice Sheet, during glacial retreat.
That might explain an accumulation of cobble stones in its shoreline
material, which are found as an ancient hilltop gravel deposit in
the hills to the south, but which are also found in younger
pre-glacial-North-Saskatchewan-River gravels.
  The glacial till ("moraine") might have been deposited from
the overlying ice after the meltwater channel was abandoned.

  It's possible that the Buck Lake basin was excavated by glacial
meltwater in an area with a pre-existing gravel cover, and it is also
possible that the Buck Lake basin is a remnant of a pre-glacial river
valley, so there is a possibility that a pre-glacial campsite on
cobble gravel happened to survive that excavation.
  But it's much more likely that any campsite in the area would have
been related to the lake, after deglaciation.
  After the local area was deglaciated, ice to the east was still
blocking drainage from the North Saskatchewan valley, so
Glacial Lake Drayton Valley was created, depositing sand along
the river valley and all around Buck Lake.
  The terraces are the result of level changes in Buck Lake since
deglaciation, as Buck Lake Creek, its outlet, cut a course to the
North Saskatchewan River This process would have been delayed at
times by beaver dams, no doubt, and dams may even have temporarily
raised lake level.
  Wave-washing of shoreline materials removed the finer material,
leaving the cobble stones behind in a beach.
  Lake ice could then have thrust or carried those cobbles up over
other near-shore material, and might also have pushed up other
moraine-like material over the cobbles.

  The "moraine" supposedly draping over the beach cobbles might also
be glacial till washed down from the slopes above. Certainly the
sand-over-organics sequence described reflects sandy material
(local bedrock is Tertiary sandstone) that was either washed out or
blown out of the till and glacial lake sediments and redeposited in
a depression that had previously been accumulating organic material
(peat).

  Add to that the effects of glaciotectonic thrusting: Buck Mountain,
to the northeast, is a several-hundred-feet-thick stack of slabs of
local bedrock thrust up as they froze onto the sole of the glacial ice,
and Buck Lake may be the result of removal of such a slab.

  The sketchy site description in _The Mammoth Trumpet_ doesn't begin
to describe the complications in the local geological history.
  I've been trying for years to work up a reasonable geomorphological
history of the Buck Mountain area, and I keep running up against a
brick wall of inadequate information.
  The sedimentary environment was too chaotic, variable, and energetic
for easy explanation, so one can hardly blame the Alberta Archaeological
Survey (now defunct) for not spending scarce resources on the site.
  Of course, one cannot fault the Chabots for their enthusiasm, either.
  If the organics associated with the rock flakes could be dated, then
that might be useful. But there is a very large possibility of
contamination from human activity (e.g. septic tank material), so
even if a Mid-Wisconsinan date was produced, it could be argued that
it had been skewed. Besides that, fine coal particles are abundant in
material derived from the local bedrock; separating out those particles
from a bulk sample of peat would be very difficult, if not impossible.

  I'm sorry; the possibilities of a pre-glacial campsite surviving at
that location are small, smaller than at most places in Alberta, and
the chances of securely dating it are even smaller.

Lamenting the demise of organised geoarchaeological investigation here,
Daryl Krupa