Cenozoic Period

The Cenozoic Era extends from 65 million years ago until the present. At the beginning of the era, submergence by the sea was still pronounced, and early Cenozoic sediments occur almost as far inland as the late Cretaceous sediments. From North Carolina northward, the most inland Coastal Plain sediments are Tertiary, not Cretaceous. This occurrence probably does not indicate that the Tertiary sea extended farther inland than the Cretaceous sea, but that Cenozoic uplift in this area has been more rapid than farther south, so that the Cretaceous sediments have been completely stripped by erosion.

(Table:Geologic Time Scale)

Recent stratigraphic evidence provides additional support for the presence of a late Cretaceous and early Tertiary sea far inland from the present Fall Line. Prowell and Christopher (2000), for example, report that Cretaceous marine deposits occur at elevations of 300 m above present sea level in south-central Tennessee. From this conditioning, they infer that most of the Cretaceous and early Cenozoic strata that once covered the Piedmont have been stripped by late Cenozoic erosion. In addition, they report that remnants of late Cretaceous and early Cenozoic beds are preserved at elevations of up to 685 m in numerous fault-bounded sediment traps as far inland as central Tennessee and western Virginia. Assuming latest Cretaceous or earliest Cenozoic deposits in the traps, this elevation translates to an uplift rate of greater than 10 m per million years.

Exceptin the earliest part of the era, erosion has been the dominant activity in the Appalachians during the Cenozoic. The history of a time interval dominated by erosion is much harder to unravel than that of an interval with extensive deposition, simply because erosion leaves behind little evidence. Thus, we know much less about geologic events in the Cenozoic than we do in, say, the Paleozoic. And yet, the modern Appalachian landscape owes its appearance almost entirely to Cenozoic processes. We know that the present Appalachian Mountains are not simply the worn-down remnants of their predecessors. The ancient mountains probably are completely gone. Our knowledge of erosion rates supports such an interpretation. Modern studies show that the Appalachians are being lowered by erosion at a rate of roughly 30 m per million years (Hack 1980; Matmon and others 2001). Let us suppose that this rate has remained the same since the rise of the original Appalachians about 300 million years ago during the late Paleozoic. Thus, 30 x 300 or 9,000 m of erosion have taken place. (In fact, the actual amount of erosion is probably much more than this, for high mountains erode at a much faster rate than do low ones). Even if we suppose that the highest peaks of the Paleozoic Appalachians were 5,000 m in altitude, higher than the highest peaks in todays Alps, the mountains would have worn away long ago had there not been more recent geological uplift were involved. In fact, the mountain landscape we see today, as opposed to the rocks themselves, are unlikely to be any older than Cenozoic. 

The Cenozoic Period produced two dramatic geological events with major implications for the landscape of the Southern Appalachian Mountains:

• Crustal Uplifting: at least part of the uplift responsible for our modern mountains probably can be attributed to isostatic adjustment in response to erosion.
• The Ice Ages: although ice sheets never covered the Southern Appalachians, the effects of cold climate on this region were strong.