Fill in the blаnks. Cоrrect spelling is essentiаl. Hоrizоntаl layers of rock are called _______ . _______ occurs when remains of dead organisms are turned to stone. The _______ fossils are found in the deepest strata. A seashell might make an imprint in mud, which forms a _______ . Plants are frequently found fossilized as _______ fossils. Coprolites (animal excrement) are an example of _______ fossils. Fossils generally become exposed as the result of millions of years of _______ .