Newark Basin Growth/EOS

Tectonic development of the Newark rift basin: Implications for the growth and evolution of half-graben and their boundary faults

Abstract--The relationship between the structural geometry of the Triassic-Jurassic Newark basin (Pennsylvania, New Jersey, and New York) and the preserved sedimentary fill provides important constraints on the evolution of the basin and its border fault system (BFS). The thickness of correlative fixed-period Milankovitch-type lacustrine cycles varies considerably within the basin and indicates that (1) subsidence was greatest near the BFS and decreased in a direction normal to the BFS; (2) subsidence was greatest at or near the center of the BFS and generally decreased toward the along-strike ends of the BFS; (3) secondary variations in basin subsidence were responsible for the development of a series of synclines and anticlines oriented perpendicular to the BFS. These results are generally consistent with recently proposed normal fault growth models in which faults lengthen as displacement accumulates through time and in which displacement is greatest at the center of the fault and diminishes toward either end.

Paleocurrent and provenance data indicate that rivers entering the basin axially and from the hanging wall block, which sloped toward the basin, acted as major sources of sediment; the footwall apparently was only a secondary and local source. It is likely that footwall uplift during normal faulting resulted in a footwall that generally sloped away from the basin. Footwall uplift--an elastic and isostatic consequence of normal faulting--may also have been responsible for the formation of rider fault blocks situated along the BFS. If the uplift rate was greater than the erosion rate, then significant topography may have been relieved through the formation of normal faults that propagated into the footwall block. Such footwall incisement is supported by stratigraphic relationships of the rider blocks.

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