Oil erosion in the United States .A. has not been adequately mapped by the Soil Conservation Service B. is causing over 30 percent of farmlands in this country to erode faster than the soil can be replaced C. is virtually under control given all the conservation practices implemented D. is highest in the northeastern states

Ageologist is working in an area with exposed sedimentary rocks and finds a well exposed sequence of stratified rocks. as he works through a thick sequence of limestone, he sees abundant large clam fossils that produce an interlocking texture suggesting a reef, but within the limestone section these clams disappear and the overlying limestone is made up primarily of fragments of corals. he now moves 50 km away and finds limestones interbedded with shales, and the limestones contain the same clam fossils he had seen previously 50 km away. as he continues through this section, the rocks become entirely limestone, and the clams disappear again with coral fossils above forming a reef structure. he concludes