4. Progress in Understanding the Structural Geology, Basin Evolution, and Tectonic History of the Eastern North American Rift System

Abstract

F ive key developments have contributed significantly to our understanding of the structural geology, basin evolution, and tectonic history of the eastern North American rift system: 1. Acquisition of new data. Over the past two decades, regional and local geologic mapping, drilling and coring, and seismic reflection profiling have increased vastly our structural and tectonic database. It is now clear that these basins are predominantly halfgraben, with generally synthetic intrabasinal faults and fault-perpendicular folds that in many cases are related to fault segmentation.2. Role of preexisting structures. The rift system is located within the Appalachian orogen, and thus the border fault systems of the rift basins consist of reactivated structures. The attitude of the reactivated faults with respect to the rift-related extension direction controlled the nature of the reactivation (dip-slip dominated versus strike-slip dominated), which affected the amount of basin subsidence and types of associated structures. The uniform dip direction of preexisting faults over large areas accounts for the lack of halfgraben polarity reversals within rift zones (e.g., the Newark-Gettysburg-Culpeper rift zone).3. Application of fault-population studies. In the past 10 years, considerable progress has been made in our understanding of the geometry and scaling relationships of populations of normal fault systems. This information is directly applicable to rift basin structural geology in that half-graben are large, normal faultbounded basins. The most relevant features of normal fault systems to basin geometry are: (a) Displacement is greatest at or near the center of a normal fault and decreases systematically to the fault tips; displacement also decreases with distance perpendicular to the fault. (b) Normal fault systems are segmented, and many fault segment boundaries are areas of (at least temporary) displacement deficits. (c) As displacement builds up on a normal fault, the fault increases in length. Consequently, rift basins consist of scoop-shaped depressions that grow longer, wider, and deeper through time. In segmented border fault systems, the scoop-shaped subbasins are separated by intrabasinal highs.4. Integration of stratigraphy and structural geology. The sedimentary deposits of half-graben are influenced by basin geometry; consequently, stratigraphy can be used to infer aspects of basin evolution and structural geology. On a local scale, thickness variations of fixedperiod Milankovitch cycles are particularly useful for From: "The

Relative timing of CAMP, rifting, continental breakup, and basin inversion: Tectonic significance

“…Synrift extensional structures are reviewed by Schlische [1993Schlische [ , 2002 and Withjack et al [1998]. Briefly, the largest-scale extensional structures are scoop-shaped half-graben produced by faultdisplacement folding [Schlische, 1995;Withjack et al, 2002] (Figure 3).…”

“…The basins of the eastern North American rift system are mostly half graben bounded by predominantly normal-slip border faults, although some basins or subbasins are bounded by oblique-slip faults [e.g., Manspeizer, 1988;Olsen and Schlische, 1990;Schlische, 1993Schlische, , 2002 ( Figure 3). The rocks within and surrounding the rift basins may be subdivided into prerift, synrift, and postrift units.…”

“…Widespread magmatism and inversion in eastern North America are related to active asthenospheric upwelling that peaked during the rift-drift transition. S o u t h e r n S e g m e n t Olsen [1997] and Schlische [2002]. b) Detail of earliest Jurassic extrusive interval (CAMP) showing correlation of basalt types by geochemistry.…”

“…The rift system and passive margin provide a natural laboratory for studying the extensional structures and rift basins associated with continental rifting, breakup, and initiation of seafloor spreading [e.g., Manspeizer, 1988;Sheridan and Grow, 1988;Schlische, 1993;Withjack et al, 1998;Schlische, 2002]. The early Mesozoic is also a critical period in Earth history, as the Triassic-Jurassic boundary marks the second largest mass extinction [e.g., Sepkowski, 1997] and is associated with one of the largest (at least in terms of area) large-igneous 2 provinces (LIP's) in the world [e.g., McHone, 1996[e.g., McHone, , 2000Marzolli et al, 1999;Olsen, 1999].…”

Multiple-stacked Hybrid Plays of lacustrine source rock intervals: Case studies from lacustrine basins in China

“…2). The rift development can be divided into pre-rift, synrift and post-rift stages according to the initiation and termination of rifting (Schlische 2003). Lacustrine basins in China with similar age and tectonic settings share comparable geological history, e.g., Cenozoic rift lacustrine basins can also be described as a succession of pre-rift, synrift, and post-rift stages, allowing them to be regionally correlated for tectonic development, sedimentary evolution, source rock and reservoir distribution (Jiang et al 2013a, b).…”