The sedimentary characteristics of the Little Badlands strata provide clues to the source area, proximity to source, directions of transportation and mode of deposition of the sediments. You will need to seek evidence in the field that will enable you to make a sedimentological interpretation for each of the startigraphic units.
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(Click on photo for enlarged version). |
The
Chalky Buttes Member is in part a conglomeratic facies. The pebbles are
of two distinct classes: subangular, soft rock lithologies such as siltstones,
and subrounded resistant lithologies, such as quartzites and cherts. You
need to provide an explanation for the different types of clasts.
(Photo Allan Ashworth) |
| Pebbles
and cobbles from the Chalky Buttes Member. The red-colored pebble in the
foreground is a volcanic porphyry. Pebble lithologies are important in
determining source area and mode of transport for the sediments. Chalky
Buttes Member pebbles have been variously interpreted to have sources
in the Bear Tooth Mountains, the Absaroka Mountains and the Black Hills.
Think of the energy in a river that transported clasts of this size to
the central part of the Williston Basin.
(Photo Allan Ashworth) |
(Click on photo for enlarged version). |
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(Click on photo for enlarged version). |
An
iron concretion from the Golden Valley Formation. What depositional or
diagentic processes supported the accumulation of iron oxides in the Golden
Valley strata?
(Photo Allan Ashworth) |
| A
flame structure in the Golden Valley Formation. How do flame structures
form?
(Photo Allan Ashworth) |
(Click on photo for enlarged version). |
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(Click on photo for enlarged version). |
Convolute
and cross-bedding in the Golden Valley Formation. What processes result
in convolute bedding?
(Photo Allan Ashworth) |
| Cross-bedding
in the Golden Valley Formation. Measurements of cross-beds provide an
important clue to the direction of transportation of the sediments.
(Photo Allan Ashworth) |
(Click on photo for enlarged version). |
