30. Highland Mills, New
Steeply dipping strata of Middle Devonian age within the Green Pond
Outlier are well-exposed in rail bed excavations for the Hudson Valley
Conrail line in Highland Mills, New York (Figure 68). To get there, follow
Route 32 North into Highland Mills and turn right onto Park Avenue, and
drive .3 mile to a gravel turnoff and parking area at the abandoned location
of the Highland Mills train station (now only an power substation remains).
Be EXTREMELY CAREFUL while examining these exposures, in that high speed
train approach almost quietly without warning (their sound is masked by
noise from the Thruway nearby). This rail line follows Woodbury Creek
northward along the eastern flank of Schunnemunk Mountain.
|Figure 68. Exposures of steeply dipping Middle Devonian sandstone
and shale along the Conrail tracks in Highland Mills, New York. The
eastern flank of Schunnemunk Mountain is on the left.
The Middle Devonian Esopus Formation (undifferentiated) crops out immediately
across from the substation. This fine-grained sandstone with interbedded
shale displays brachiopod shell hash layers preserved as iron-stained
molds and shows evidence of heavy bioturbation by marine invertebrates
(Figure 69). The strata is dipping steeply in a northwest direction at
about a 65 tilt. The walk northward along the path besides the tracks
(not on the tracks!) provides an opportunity to examine progressively
younger units which are increasingly less fossiliferous and more haley
(an indication of progressively deepening water conditions). About a mile
northward along the tracks are exposures of the brownish-red Bellvale
Sandstone. From here, the strata grows progressively coarser-grained up-section
until coarse puddingstone conglomerate dominates the ridge of Schunnemunk
Mountain (on the west side of the valley).
|Figure 69. Molds of brachiopods in sandstone from the Middle Devonian
Highland Mills, New York.