Along-axis segmentation and growth history of the Rome trough in the central Appalachian basin

The Rome trough, a northeast-trending graben, is that part of the Cambrian interior rift system that extends into the central Appalachian foreland bas in in eastern North America. On the basis of changes in graben polarity and rock thickness shown from exploration and production wells, seismic lines, and gravity and magnetic intensity maps, we divide the trough into the eas tern Kentucky, southern West Virginia, and northern West Virginia segments. In eastern Kentucky, the master synthetic fault zone consists of several m ajor faults on the northwestern side of the trough where the most significa nt thickness and facies changes occur. In southern West Virginia, however, a single master synthetic fault, called the East-Margin fault, is located o n the southeastern side of the trough. Syndepositional motion along that fa ult controlled the concentrated deposition of both the rift and postrift se quences. The East-Margin fault continues northward into the northern West V irginia segment, apparently with less stratigraphic effect on postrift sequ ences, and a second major normal fault, the Interior fault, developed in th e northern West Virginia segment. These three rift segments are separated b y two basement structures interpreted as two accommodation zones extending approximately along the 38th parallel and Burning-Mann lineaments. Computer -aided interpretation of seismic data and subsurface geologic mapping indic ate that the Rome trough experienced several major phases of deformation th roughout the Paleozoic. From the Early(?)-Middle Cambrian (pre-Copper Ridge deposition), rapid extension and rifting occurred in association with the opening of the Iapetus-Theic Ocean at the continental margin. The Late Camb rian-Middle Ordovician phase (Copper Ridge to Black River deposition) was d ominated by slow differential subsidence, forming a successor sag basin tha t may have been caused by postrift thermal contraction on the passive conti nental margin. Faults of the Rome trough were less active from the Late Ord ovician- Pennsylvanian (post-Trenton deposition), but low-relief inversion structures began to form as the Appalachian foreland started to develop. Th ese three major phases of deformation are speculated to be responsible for the vertical stacking of different structural styles and depositional seque nces that may have affected potential reservoir facies, trapping geometry, and hydrocarbon accumulation.