You observe a distinct, red sandstone rock body about 50 m thick that is depositionally overlain by a red shale with interbedded gypsum and you follow this boundary in the rock bodies for 1 km until you cross a fault which has displaced the boundary between the two rock bodies. You walk along the fault and see a boundary between a 50 m thick red sandstone and overlying red shale interbedded with gypsum. You conclude______ .
A) the second exposure of sandstone, shale and gypsum correlates to the first, and the boundary between the sandstone and shale is the same stratigraphic horizon
B) this new exposure of sandstone, shale and gypsum must be a different age rock unit
C) the stratigraphic section must have been inverted by the deformation; the rocks are upside down
D) this is impossibly complex; the fault broke up all the rocks

Question

Quizplus · Accepted Answer

The fact that the same rock units are present in both exposures, and that they have the same thickness and depositional sequence, suggests that they correspond to each other and the boundary between sandstone and shale is at the same stratigraphic horizon. The fault likely caused displacement but did not alter the overall sequence of the rock units. Option B can be ruled out as there is no evidence to suggest a different age rock unit being exposed. Option C is unlikely as there is no evidence that the stratigraphy has been inverted. Option D is incorrect as faults do not necessarily break up all rocks, and there is no evidence to suggest that this is the case here.

You Observe a Distinct, Red Sandstone Rock Body About 50