Paper No. 17
Presentation Time: 8:00 AM-12:00 PM
MESOZOIC DRAINAGE EVOLUTION AND PALEOGEOGRAPHY OF THE EASTERN UNITED STATES
The Upper Jurassic Norphlet Formation eolian sandstone in the subsurface of the southeastern U.S. contains detrital zircon U-Pb ages that reflect mixing of Laurentian and Gondwanan ages that form four major populations: 250-500 Ma, 500-700 Ma, 900-1400 Ma, and 1950-2250 Ma. The origin of Neoproterzoic zircon in the Norphlet Formation could be from the Carolina terrane of the east-central U.S. or the Suwannee terrane of Florida. If Neoproterzoic zircon in the Norphlet Formation was derived from the Carolina terrane, then detrital zircon age signatures observed in the Norphlet Formation should be observed in the Triassic-Jurassic Newark Supergroup deposits preserved in Central Atlantic margin rift basins. It has been hypothesized that the Newark Supergroup basins consisted of half-grabens, some of which became stratigraphically linked during the latest stage of rifting. In order to test this idea, detrital zircon ages can be compared between Norphlet Fm. sandstone and Newark Supergroup clastics of the Deep River basin in North Carolina, one of the southernmost exposures of these Mesozoic rift basins along the Central Atlantic Margin. Two samples of the Chatham Group were collected from the Triassic sandstone of the Deep River basin for detrital zircon provenance analysis. The Sanford Formation is exposed in a 3 m thick outcrop located Along NC 42, 6 km E of Deep River., 10 km NW of Sanford, NC. The Sanford Formation here consists of gray sandstone, reddish siltstone, and grey fragmented mudstone/shale with poorly sorted subangular to rounded pebble-boulder conglomerate with clay/silt matrix. Beds in the sampled outcrop exhibited a coarsening upwards sequence, evident of higher energy depositional conditions over time. The Pekin Formation is composed of medium-bedded brown fine-grained sandstone to siltstone interbedded with laminated shale beds. Detrital zircon provenance analysis will be used to determine if these alluvial-lacustrine Triassic deposits were recycled in the to supply sediment to the middle Jurassic Norphlet erg.