The geologic history of Texas, like the geologic history of the rest of
the earth, is recorded primarily in marine sedimentary rocks. These
rocks provide some knowledge of the early geography and the first
inhabitants of what is now the State of Texas. Most of these rocks were
formed from sediments deposited in shallow seas which covered parts of
the State at various times in earth history.
By studying these rocks and their relations to each other, geologists
have established a geologic column for Texas.