Laboratory Manual for Introductory Geology 4e

GEOTOURS EXERCISE 6
Interpreting Depositional Environments for Sedimentary Rocks (continued )
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whose ancient depositional environment might have been similar. If the Sandhills area becomes lithified, what
sedimentary rock type (be as specific as you can) with what sedimentary structure is likely to form?
rock type
structure
(b) Expand the Transgressions/Regressions folder. Check all of the Cuba placemarks and double-click one of the
placemark icons to fly to the northern shore of Cuba. Here, sand is deposited in the area nearest the shore, finegrained
muds are deposited at an intermediate distance from the shore, and lime muds rich in precipitated calcite
form farthest from the shore. Consider
what the vertical stacking of deposits
would be if sea level fell (regression)
and if sea level rose (transgression)
by imagining the shoreline migrating
seaward and landward, respectively.
Now check all of the Grand Canyon
placemarks and double-click one of
the placemark icons to fly to the Grand
Canyon in Arizona. At this location, note
the following sequence of Cambrian
rock units: Tapeats Sandstone (lowest
rock unit), Bright Angel Shale (middle
rock unit), and Muav Limestone
(top rock unit). The vertical stacking
of these units represents either a
regression (fall) or transgression
(rise) of sea level. Which occurred
in this area during the Cambrian?
6.8 APPLYING YOUR KNOWLEDGE TO STRATIGRAPHY
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