EXTENT OF SUWANNEE TERRANE RE-EVALUATED OFFSHORE: IMPLICATIONS FOR THE LOCATION OF THE ALLEGHENIAN SUTURE

Re-analysis of legacy 2D seismic reflection and well data from the offshore of the southeastern United States reveals a previously unmapped lower Paleozoic sedimentary section identified in three deep offshore wells. Paleozoic strata have been known onshore in Florida since the 1930’s, and were subsequently identified to be part of the exotic Suwannee terrane. The COST GE-1 and Transco 1005-1 wells drilled in the late 1970’s on the Georgia continental shelf both encountered Paleozoic strata in the lower sections of the wells, but have not previously been rigorously integrated with the Paleozoic strata onshore. The Paleozoic platform sequence in offshore seismic profiles is identified as a package of low-frequency, sub-horizontal reflectors which are clearly discordant with the overlying stratigraphy above the post rift unconformity (PRU). The inferred base of the Paleozoic sequence is marked by the downward diminution of parallel seismic reflectors, as well as a change in seismic velocities observed in offshore seismic refraction surveys. These observations suggest a stratigraphic thickness for the Paleozoic sequence of 3-6 km that can be mapped continuously updip of the Florida-Hatteras slope. Recognition of these exotic strata offshore, and correlation across 2D MCS reflection profiles, implies that the Suwannee terrane continues northward, across the continental shelf of Florida and Georgia, at least to North Carolina, providing new insight into the true extent of the Suwannee terrane and possible location of the Alleghenian suture.