Pleistocene shorelines and coastal rivers: Sensitive potential indicators of Quaternary tectonism along the Atlantic Coastal Plain of North America

Our models show patterns refl ecting local fault control on both shoreline regression and river defl ections along the Atlantic Coastal Plain. In these models, maximum displacement is assumed to be at the center of a fault, and both uplifts and downwarps are assumed to be of sufficient magnitude to infl uence surface processes. Models show regional shoreline regression: (1A) without localized uplifts; (1B) with different rates of regional uplift at either end; (1C) without any localized uplifts but with a large river-dominated delta; (2A) with a fault parallel to the shoreline with seaward side down or (2B) with seaward side up; and (3) with a fault perpendicular to the shoreline. Model 1A has consistently spaced parallel shorelines and an absence of river defl ections, such as characterizes most of the late Pleistocene coastal plain across Georgia. Model 1B has divergence of shorelines toward and defl ection of rivers away from the end with greater uplift. Model 1C has seaward defl ections of shorelines with spacing dependent upon rates of sediment infl ux and removal by coastal processes. Models 2A and 2B represent interruptions of model 1 patterns. Both produce a seaward defl ection and wider spacing of younger shorelines on the uplifted side of the fault with associated river defl ections toward the margins of the uplift. Both also produce a landward defl ection and closer spacing of younger shorelines coupled with convergence of rivers toward the downdropped basin. Model 3 produces a seaward defl ection and wider spacing of older shorelines across the uplift associated with river defl ections toward the margins of the uplift on one side of the fault. On the other side, there is a landward defl ection and narrower spacing of younger shorelines on the downdropped side of the fault where river defl ections merge toward the lowest area.