Paleozoic North America has experienced multiple mountain building events, from Ordovician to Permian, on all margins of the continent. These have had a profound effect on the resulting complex basins and their associated petroleum systems. Subsequent uplift, erosion and overprinting of these ancient systems impedes the direct observation of their tectonic history. However, the basin sedimentary records are more complete, and provide additional insights into the timing and style of the mountain building events. In this study, we employ ~90 1D basin models, ~30 inverse flexural models, isopachs, and paleogeographic maps to better understand the Paleozoic history of North America. From this screening, four thematic learnings emerge:

Constraints on the magnitude, timing, and location of collisional events. For the final Appalachian Orogeny, the Alleghanian event, the onset of flexural subsidence becomes younger to the northeast. Whereas the Ouachita Orogeny youngs to the southwest. These observations suggest the docking of Gondwana in the Pennsylvanian-Permian was diachronous due to a progressive closure from an indenter in the Alabama-Kentucky area. The influence on stratigraphy and petroleum systems is profound – e.g., the deep-water systems of the Arkoma-Fort Worth-Val Verde system are dominantly Atokan in the east and Wolfcampian in the west.

Kinematic linkages between continent margin and interior. “Sag” basins, whose origins remain cryptic, can be tied to adjacent orogenies. The Michigan Basin has synchronous timing, and a similar evaporite fill as the Salinic portion of the Appalachian foreland. And the Williston Basin appears tied to the north Antler (Liard) foreland with Middle Devonian to Early Mississippian subsidence and deformation (e.g., Nesson Anticline). Ancestral Rocky Mountain (ARM) basins of the continental interior also share kinematic linkages, based on subsidence timing. For example, two phases of subsidence are shared for the Marathon Orogenic Belt (Val Verde-Marfa) and greater Permian Basin (Midland-Delaware-Orogrande). Initially, a Virgillian-Wolfcampian period of variable rapid subsidence (basins) and synchronous uplift (platforms) occurs. Followed by a period of long-wavelength subsidence (Leonardian-Ochoan) that flood the platforms and facilitates the development of carbonate reservoirs, such as the Clearfork and San Andres.    

Controls sedimentary fill character and source rocks. Often, the onset of rapid subsidence associated with orogenesis is marked by a rapid transgression and condensed section that is associated with marine source rocks and shale reservoirs. As sedimentation catches up to the increased accommodation, a thick sedimentary wedge progressively fills in the flexural basin. This pattern is observed for the Utica (Taconic), Marcellus (Acadian), Wolfcamp (Delaware and Midland), Horn River (Liard), and Gothic/Cane Creek/etc. (Paradox) source rocks.

Reconstruction of thick Permian basin fill in exhumed basins. Many of these basins have experienced significant post-Paleozoic erosion by vertical unroofing and/or subsequent deformation. This has made understanding of the latest Paleozoic basin history difficult. High vitrinite reflectance in outcropping or shallow strata indicates significant burial and ensuing removal. In most cases, this additional burial cannot be attributed to significant Mesozoic-Cenozoic sedimentation. Using calibrated basin models, significant upper Pennsylvanian and Permian sections have been restored in a number of these basins.  Estimates of the eroded latest Paleozoic section include the Appalachian (~3.5 km), Black Warrior (~3 km), Arkoma (~3 km), and Fort Worth (~2.5 km) basins. This burial was critical in the maturation of important source rocks/shale reservoirs in these basins.