|Geology:||(click on an image for a larger view)|
In the vicinity of
Twiggtown the Helderberg Formation is comprised of three members totaling
about 325 feet in thickness. Twiggs Cave is developed in a series of dark
gray to black crystalline limestone beds that lie about 25 feet below
the base of the Coeymans Member and 250 feet above the base of the Keyser
Member. The limestone is somewhat knobby and is high in clay content.
The cave is developed on the western side of an anticline. The beds dip
60º W and strike N 40º E. A series of master joints trends N
40º E and dips 60º E. A series of subordinate vertical joints
trends N 50º W.
Straight Way in Twiggs Cave
| The entrance
to Twiggs Cave is through a vertical shaft, 25 feet deep, 4 to 8 feet long,
and 1 foot wide. At the base of the shaft is a "Z" shaped passage
about 40 feet long and sloping 45º which connects with the first room.
This room has two "mud glaciers" at its south end that are slowly
moving and covering the floor. The cave continues in a northerly direction
from the is room as a passage, the Straightway, that is 10 to 15 feet wide
and 10 feet high. Just north of the first room is a pile of broken rock
leading down 25 feet to the level of the Straightway. The floor of the Straightway
is made of fallen rocks to a considerable depth and many minor passages
exist beneath the main level. The Straightway, 85 feet long, ends in two
chimneys at the base of which is a deep well. A narrow, crevice-like passage
leads off the base of the first chimney and continues into a small room
that ends in a mud wall. A small crawlway, 4 feet in diameter, leads off
the west side and curves around to a narrow clay shelf at its junction with
the second major fissure passage. Here is a row of six pits leading to a
lower tunnel. The largest pit, the Kings Chair, affords access to the lower
level that is a low tunnel 3 feet wide, 2 to 5 feet high, and 40 feet long.
The passage continues along the base of a high sloping crevice. The passage
is 15 feet wide and slopes steeply for 100 feet to a drop of 14 feet. This
point, 192 feet below and 375 feet from the entrance, is at the stream level
of the cave.
The stream enters this section of the cave from below by a steeply sloping and curving shaft over 75 feet deep. The stream forms three shallow pools, each about 10 feet long, and then flows along the floor of the cave. Twenty feet beyond the drop to the water level is a shallow pit into which the stream plunges with a loud roar. The cave continues as an ever narrowing passage, decreasing from 20 feet high and 10 feet wide to 3 feet high and 2 feet wide. In places the route of traverse is in the stream bed, in other places along a clay ledge above the stream. At 120 feet this passage ends in a small tunnel 2 feet high and 1½ feet wide, the floor of which is occupied by the stream. This passage, which necessitates a crawl, is 25 feet long and ends in a narrow crevice-like passage 10 feet high, 4 feet wide, and 10 feet long. At the southwest corner is a narrow slit in the floor down which the stream plunges to a lower level. This falls is over 50 feet deep. Bottom was not reached in soundings.
In 1946 a small tunnel was excavated through packed clay and gravel to a low passage that leads 30 feet to a pit which is 40 feet deep and 5 feet in diameter at the top. The base of the pit is a slit 1 foot wide which leads off into a crevice passage less than a foot wide. Traverse of this passage was not possible, but the cave appears to open up somewhat 30 feet beyond. The floor at the base of the pit is covered by a thin veneer of yellow clay of recent deposition indicating that the stream backs up to this level. The base of the pit is 290 feet below and 750 feet from the entrance.
Above the Straightway is another passage resulting from the fall of large blocks of limestone that form the ceiling of the Straightway and the floor of the upper level. The two levels are connected by a number of openings between the rocks, but access to the upper level is afforded at only one point. At the south end of the Straightway, near the 25 foot drop, is a flow-stone ledge on the west wall that slopes steeply to the east. A traverse diagonally across the flowstone leads to a small hole that gives access to the upper level. The upper level passage is 10 feet wide and extends for 100 feet as a fissure similar to the lower levels. The fissure is 30 feet high and tapers out at both ends. Several massive stalactite formations are developed on the east side of the passage, and one of them gives beautiful musical tones when struck.
An upper level exists above the Kings Chair. It is a ledge 10 feet wide that lies 30 feet above the base of the fissure passage. At the north end this level develops as a separate passage extending over 100 feet.
(from ES3 -Caves of Maryland)
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