Unformatted text preview: this valley, its waters
draining westward across a low
glacial retreat uncovered a lower
outlet north of the area now marked
by the New Jersey - New York State TO 23 KURD
During this time, the lake
drained northeastward over a plug of thick till. Its water level lowered
by as much as 20 feet, but it did not completely drain. The lake
persisted well into recent time before decayed vegetation filled it in,
forming a swamp. The bouldery area along the swamp’s modern
outlet is called a lag deposit. It was formed by the small stream
that drained the lake, which eroded the fine-grained sediment from
the till it was flowing over, leaving behind the heavier stones. The lower part of the slope on the east side of the swamp consists
of a thin layer of till. In a few places, bedrock is very close to the
surface, as shown by irregular areas of angular boulders. Large
outcrops of Shawangunk Formation form the upper part of the
slope. These rocks dip to the southeast, and below them lies a
narrow apron of conglomerate and quartzite talus. Bedding on the
lower part of the hillslope dips northwestward, which shows that
the talus apron conceals an anticlinal fold axis.
Figure 19 shows the change in forest cover around High Point from
the close of the last ice age to the present; a period of 11,000 years.
It is based on a pollen diagram of a core retrieved from Cedar Swamp.
The lower part of the record shows that spruce and pine formed the
dominant forest cover. The high percentage of spruce, which favors
a climate much cooler than that now present at High Point, shows
that the forest cover 10,000 years ago was similar to the presentday forests of northern Maine and southern Canada. Higher up
in the record, a rise in the percentage of oak, accompanied by
decreasing pine and disappearance of spruce, record the transition
to a temperate forest of mixed hardwoods dominated by oak. The
predominance of oak at the 14-fo...
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