Stratigraphic and tectonic evolution of the Pangean rift basins of the central Atlantic margin.

One of my main research interests is the evolution of continental rifts, with a focus on the Pangea-breakup rifts of the circum-Atlantic margin.  My studies have focused, in particular, on the Hartford basin (Conn.-Mass.), the Pomperaug basin (Conn.), the Richmond and Taylorsville basins (Virginia), the Argana basin (Morocco), along with substantial work in the Fundy basin New Brunswick and Nova Scotia, Canada), the Danville-Dan River basin (Virginia-N. Carolina), and the Culpeper basin (Virginia).

This work has relevance for:
    understanding the earliest stage of development of passive margins;
    creating a high-resolution paleoclimatic record for reconstructions the late Triassic and early Jurassic;
    exploring the late Triassic extinction and the subsequent recovery of fauna and flora;
    identifying potential oil and gas reserves adjacent to major population centers;
    locating regional, deep, groundwater aquifers;
    creation of a hemispheric paleogeographic matrix of the late Triassic;
    unraveling tectonic and climatic controls on continental sedimentation.

 
Fig. 1. Surface and Subsurface rifts in the Mid-Atlantic region.    Fig. 2.  The Taylorsville and Richmond basins.
                                                                                                    
     
My Ph.D. thesis studies determined a comprehensive tectono-stratigraphic model for the evolution of the Taylorsville-Richmond basin system, based on extensive field work and unprecedented access to over 6,800 m of continuous core, more than 7,000 m of  exploratory well cuttings, extensive seismic profiles, down-hole geophysical data donated to Lamont-Doherty Earth Observatory (LDEO) from Texaco.



Fig. 3.  High-res lithologic columns of continuous cores.               Fig. 4.   Analysis of test well cuttings.

Lithostratigraphic and paleomagnetic correlation of the data set, in conjunction with analysis of seismic reflection profiles, revealed that the Taylorsville-Richmond basins began as a series of small-scale rifts distributed over the field of continental extension.  Fault-length scaling relationships indicate that faults grow longer as displacement increases.  As extension, and fault displacement progressed in the sub-regional rifts, some became abandoned as others dominated to become regional-scale half-graben.  The transition from several sub-regional basins to two (Taylorsville and Richmond) regional scale rifts is recognized as an unconformity.  Post-rift inversion placed an overlay of stratal deformation over earlier structural and stratigraphic features.


                         Fig. 5.   Potomac River seismic line with interpretation based on subsurface data set.


 My model reveals the development of rift system from a series of incipient, small-scale rifts to regional-scale half-graben.  Prior to my work, there was no evidence for the broad shift from distributed small-scale rifts (10's km) to regional features that dominate the regional (100's km) extensional stress field.


                                
                                    Fig. 6. (a,b).  Evolution of rift drainage systems
       



I also employed high-resolution paleomagnetic reversal stratigraphy to confirm and sharpen lithostratigraphic correlations of deep test wells.  In the course of my study, I needed to erect a comprehensive, first-order stratigraphic scheme for lithologic units observed in the field and in the subsurface data set.  


                                           Fig. 7.  Tectono-stratigraphic correlation of the Taylorsville and Richmond basins.