EVIDENCE FOR RECENT UPLIFT OF THE APPALACHIANS FROM DETRITAL ZIRCON GEOCHRONOLOGY

The southern and central (SC) Appalachian landscapes have undergone significant change since the Paleozoic. Recent uplift in the SC Appalachians is a product of tectonism during the Tertiary, and not related to long-term static crustal processes. Tertiary uplift produced rearrangement of stream patterns, migration of the eastern continental drainage divide, and increased rates of erosion during periods of uplift. The Gulf Coastal Plain is the main repository of sediments derived from the North American continent during the Mesozoic and Cenozoic. Our study is aimed at documenting evidence of Tertiary uplift of the SC Appalachians based on detrital zircon ages of sediment samples from the Gulf Coastal Plain in FL, AL, and MS. Increased amounts of sedimentation in the Gulf Coastal Plain is a proxy for Late Cretaceous-Eocene and late Tertiary tectonic uplift in the SC Appalachians. Detrital zircon age data from late Miocene-Pliocene sediments in FL, AL and MS record five major age populations: (1) very old 2.5 Ga age peaks in most samples, indicating Appalachian source zircons ultimately derived from the Superior province in the Canadian Shield; (2) a major Grenville (1.0 Ga) age peak, indicating Appalachian source rocks for the sediments; (3) a 600 Ma age peak in most samples indicating a Carolina superterrane source; (4) 480, 400, and 330 Ma age peaks in all samples, indicating Taconic, Acadian, and Alleghanian orogeny sources; and (5) Late Cretaceous and early Tertiary (Paleocene, Eocene, Miocene) age peaks in more than half of the samples. Dominance of Appalachian provenance in the detrital zircons suggests tectonic uplift in the SC Appalachians during the Tertiary is recorded by increased sedimentation in the late Miocene-early Pliocene sediments in the lower Gulf Coastal Plain. Late Cretaceous zircons range between 99-67 m.y, while Tertiary zircons range between 64-24 m.y. Younger zircons may be derived from Laramide uplifts in the western U.S. suggesting that late Tertiary Appalachian uplift was coeval with late Laramide uplift.