1. The photo below was taken near Menlo, Georgia, along Route 48. There is a thi

Question

1. The photo below was taken near Menlo, Georgia, along Route 48. There is a thick resistant layer of conglomeratic sandstone bed overlying silty shale, with a thin coal seam (less than an inch thick) at the contact between the two. tone overlying coal and shale, northwestern Georgia. a. In the box beside the photo, draw a simple stratigraphic section to correspond to the rock outcrop in the photo. Be sure to use the proper lithologic symbols. Fill the entire box with beds and lithologic symbols. b. Considering that you have a coal deposit between the sand and the shale, which sedimentary environments are likely to be represented here? c. If you were in the field with the people in the photo, what would you look for to distinguish whether these rocks were marine deposits or nonmarine deposits?

Explanation / Answer

a.

b. Presence of coal represents a swampy environment. Swamps represent forested wetlands adjacent to rivers or lakes. They host freshwater or brackish water or sea water. Stagnant water and low topographic relief are characters of swamps.

c. The presence of coal seam enabled the field geologists to decipher whether the rocks were marine or non marine. Coal is always formed in marine environment - swamps are adjacent to the rivers or lakes. Moreover, in the stratigraphic section, conglomeratic sandstone lies above silty shale- this is a coarsening upwards sequence. This indicates a marine environment. Thus, these two conditions represent a marine environment.

Conglomeratic Sandstone Thin coal seam Silty Shale

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