Black shales contain abundant ________ and were probably deposited in a/an ________ environment.

Question

Quizplus · Accepted Answer

Black shales are typically rich in organic matter, which is why they appear dark. This organic matter accumulates in anoxic (oxygen-deprived) environments, which prevent it from oxidizing and decomposing. Iron sulfide minerals can also be present in black shales, forming as a result of bacterial metabolism in anoxic conditions. Calcium carbonate is more likely to form in shallow, tropical marine environments. Iron oxides may be present in sedimentary rocks that formed in more oxygenated conditions, such as red sandstones. Glass fragments would suggest a volcanic origin for the sedimentary rock, rather than deposition in a specific environment.

Black Shales Contain Abundant ________ and Were Probably Deposited in A/an