Paleoclimatic information for the Miocene and Pliocene is scarce or lacking in eastern United States because of a general absence of fossils in the nonmarine upper Tertiary sedimentary rocks. Information previously available was based chiefly on floral evidence from a few widely scattered locations in the Atlantic and Gulf coastal plains, or represented extension of climatic zones which were determined from fossiliferous units in the Mid-Continent or Western Interior.

X-ray and petrographic information from land-derived Miocene and Pliocene deposits in northeastern and southeastern United States clearly reflects climatic conditions during the late Tertiary and verifies the conclusion that subtropical conditions did prevail as far north as northern New Jersey during the Miocene and Pliocene.

In addition, mineralogic evidence from Miocene sedimentary rocks in the Gulf Coast strongly indicates that the sediments deposited on the Florida platform were not derived from material eroded in the Rocky Mountain drainage basin, as previously has been proposed, but instead represent detritus carried southward by rivers from the southern Appalachians and Piedmont and distributed by longshore currents.