(base map and topo) Detailed measurements of clast volume and orientation show four
sequences where boulder deposits exhibit an increase in mean clast volume downslope,
suggesting discrete events and landforms.
(Figure Plan and Cross Sectional View) Plan and cross section views of the topography
between stations 9 and 11, depicting weakly-developed benches and escarpments.
(cross section pit) Longitudinal profile of boulder front, near station 9. The fabric of this
deposit is dominantly open framework. Note the weak stratification
as shown by the dashed lines. Numbered boulders correspond to
respective boulders seen in photo of file ‘pit’.
(pit) Photo of excavation pit of boulder front, near station 9. Individual numbered
boulders are identified in figure in file ‘cross section pit’. The
red line marks the upper boundary of the excavation.
(cambering quartzite) Quartzite columns displaced by cambering and
toppling near station 2. The tilt of the red lines
demonstrates the toppling of the nearly horizontal
beds after cambering has opened and separated the
blocks along joint planes.
(tor) Shattered tor (height ~10 m) at Blackrock summit, near station 3. Quartzite blocks
break along A) bedding planes and B) joint planes.
(block slope) View towards northeast of upper widest part of block slope near station 4.
Block slope is approximately 175 m in width, and mean volume of boulders is
0.8 cubic m. Arrow shows person for scale.
(protalus rampart) "Curious" ridge and furrow feature at the toe of the block slope shown
in photo of the file ‘talus field’. Note the geologists for scale. Landform may be a
protalus rampart.
(talus field) Prominent block slopes west of Blackrock, forming from quartzites
of the Harpers and Antietam formations.