Notes from tape recording with Dr. Duane Braun’s visit to campus.
Looking at map in the lab:
Ice direction in this area is from N30E to S30W.
Till shadows form on the lee of hills.
Stream Valleys are armored.
Ice retreated from this area about 17-18000 yrs ago. May take as much as 4000 years for forests
to mature afterwards. First would come sedge/grass tundra on unstable slopes (as seen in
Alaska).
Bedrock in this area is Late Devonian (~375 m.y.) and is the Catskill formation of sandstone and
shale.
White (1881) is the last reference.
Lackawanna State Park has bedrock on the south (at dam) and ~150 of till on the north.
Till keeps baseflows up.
Baylor’s Lake is an old glacial lake blocked by till.
Legend of map
Qp = peat
R = rock exposed or within 2”
Qw=wetland
Qwt=till
Q=Quaternary
W=Wisconsin
Crossing Tunkhannock Creek
Nice riffle and pool stream with a few boulders
Salamander slough-often holds water all summer; layer below doesn’t have to be completely
impervious because there is groundwater seepage through the fine-grained sediments from the
hillside.
Tunkhannock Creek-on hillside near bridge, till is about 50 feet over bedrock. The stream is
‘hungup’ on bedrock. There are some beautiful bedrock falls. The stream has not been able to
cut down to its original depth in this whole stretch. There are some incised meanders
downstream. The stream meanders in the incised bedrock valley, a meandering valley, if you
will. The present stream is a lot straighter than that and it has gotten hung up on some of the
incised meander loops and hasn’t been able to cut down to its original floor.
First gully up the trail, at first wooden bridge:
Colluviums is visible; relates to periglacial environment. Frozen in winter, gradually thawing in
warmer season, this layer ‘flowed’ downhill (“gelifluction”?). Now, the slope is stabilized,
covered with vegetation, no longer moves as it did.
This area had a warm-based glacier, melting at the bottom and releasing debris.
Lodgement till is this debris being plastered to the bedrock by the full weight of the glacier.
The boulders provide the stream with ‘self-armoring’ as they move downslope and prevent the
stream from being able to cut back further.
This gully isn’t cut very deep . . . the next one over is, but it has a much bigger drainage area.
This area would look like a miniature grand canyon with its stepped appearance if it hadn’t been
glaciated. This would be due to the alternation of sandstone and shale layers. The hummocky
landscape suggests till (in the absence of the stepped appearance.)
There probably was about 3000 feet of ice in this area (based on profiles of existing ice sheets
and estimates of isostatic rebound after removal of the ice in the area of the Great Lakes). We’ve
probably had about 100 feet of rebound in this area. Mantle material oozes out under the weight
of the ice. When it’s gone, it oozes back in. Kind of like a waterbed (actually a silly putty bed),
but on a slower basis.
Headed toward rock outcrops by sewage plant.
The stonewalls tell us something. Notice that there are some rounded ones in with the tabular
ones. The rounded ones tell us that there is till. If they are only tabular, probably bedrock close
to the surface.
Ice flow in this area is form N30E to S30W. This can be deflected by local topography, as has
been done locally by Elk Mountain. The basal ice went around the mountain, as indicated by
striations that were deflected about 30 degrees at its base. At the summit, the flow was in the
normally expected direction.
Parenthetic Comments about the New Milford Sluiceway:
A classic, monster meltwater stream, it carved the deep sluiceway that route 11 follows through
New Milford. It’s a narrow deep valley with several narrow lakes. 1200 feet of rock were
removed up there. It’s a miniature Grand Canyon of PA. With a couple of more glaciations, the
Susquehanna will come down through there.
Back to the sewage plant area.
“Joe-average” sandstones in this area, which are river-channel SS, part of a deltaic system.
Some are crossbedded; there are some ripple marks. These are the types of SS that are formed
into Bluestone due to the nice planar bedding.
END of TAPE SIDE ONE.
TAPE SIDE 2:
Going across the bridge in Factoryville and headed up Church Street to get to the bedrock
ridgetop in search of glacial striations. Hard to find because the bedrock has been exposed to
atmospheric acids, etc., since glacier left. Most have been weathered away. We went into an old
quarry on the west side of the road. Braun found some striations (using water helps) and used
his Brunton to measure them as from N40E to S40W. Can find up to 10-degree variance in any
outcrop. He uses an average. These were probably from the recession phase. In contrast to
deposition of till in valleys that are transverse to ice flow. These were probably filled during the
in advancing state.
At Nature’s Niche along Rte 6 & 11 where they have excavated into a hillside, including around
a pole. It is a mound of pretty compact sand, because the glacier sat upon it; hence this is QWIC
on the map, ice-stratified contact drift. (Sand or gravel deposited under or next to the ice, often
quite rapidly. It has been ‘washed’, so clay and silt have for the most part been washed out. It is
fine to medium sand. It shows chaotic bedding. Many rounded clasts. It’s the best example of
sand and gravel in the quad. No eskers in this area.
Turned off Seamans Rd. on to Newcombe Rd. Railroad cut is through all till which is at least 30
feet. Nearby is a RR cut through bedrock. This info is used to estimate minimum till depths.
Continued down the same road until we came into the Dalton Quad. Last home on the left was
Halstead. We went up a one-sided bedrock valley. It is transverse to the direction of ice
advance. The glacier created a till shadow. The stream here is against the west, bedrock side of
the valley.
TAPE SIDE III
East Branch Tunkhannock Creek is cutting through an outwash terrace of sand and gravel, one of
the few instances of this around here. It’s a bigger creek, sub parallel to the ice flow, so the ice
can help to scour it. It’s wider because of all the water coming down the sluiceway, carrying
sand and gravel. The present day stream is cutting down through the outwash, the meltwater
floodplain.
Tunkhannock Viaduct was built there because it could take advantage of the sluiceway to NY. It
has to face ‘only’ 1200 feet of relief. The competing route came out of the north end of the
syncline north of Carbondale and Forest City. There they had to face 2000 feet. This made the
Nicholson route less expensive for moving coal out. Large capital outlay, but less energy spent
on every trip.
We’re headed into another glacial. Global warming will be a blip. We’ll run out of fossil fuels
shortly (speaking geologically). The present interglacial is as long as the others in the last million
years. And there have only been 2 others this warm in the last million years. He expects
glaciation to begin within a few thousand years.
Little Rocky Glen
Normal stream erosion and a bedrock ledge. Little pothole. Every time you have a sizable
stream going over a bedrock ledge you’ll have potholes, which are formed by vortices in the
water. When they come upon an imperfection in the stream bottom, particles collect there which
act as grindstone. Highest outcrop in the area. This is an area of significant Holocene (postglacial) erosion. This outcrop was cut/eroded since the glacier left. Potholes help this. A couple
get going and coalesce forming a slot canyon. This sandstone is moderately resistant. It’s fairly
hard stuff. If it was shale, it would be a lot deeper (more easily cut). Reminiscent of The Tubs,
which is on tuffer stuff, but with a greater slope. Needs water volume, slope, and tools. Ripple
marks here in the sandstone.
Upper Devonian Sedimentation in Susquehanna County and Hydrology, Glacial Geology and Environmental
Geology of the Wyoming-Lackawanna Valley. Thirty-sixth Annual Field Conference of Pennsylvania
Geologists, 1971.
The first trip presents a discussion of the geology, composition, texture, and physical properties of the flagstones of
northeastern Pennsylvania and of the properties of flagstone that affect their discovery, development, and use. The
second shows environmental problems resulting from the removal of the coal in the northern anthracite field and
examines exposures of Pleistocene deposits.
Leaders: S. A. Krajewski, E. G. Williams, J. R. Hollowell
Date: October 8-9, 1971
We moved to a new site.
Just north of Carpenter Hollow on the quad.
Just above Bardwell on the map is a hill, elevaton 881, which Duane says is a blob of till which
probably extended across the stream , blocking it and creating a lake upstream toward Keystone.
80 feet above current creek level are fine-grained (=fairly quiet deposition) silts. Above that,
gravel. The creek has cut through all this. These glacial lakes, impounded by till, are fairly
common in this area.