02382nas a2200205   4500008004100000245007800041210006900119300001200188490000800200520172700208653003301935653001901968653001601987653002902003653003102032653002702063100002502090700001402115856004702129       2000                        eng d00aBulge Migration and Pinnacle Reef Development, Devonian Appalachian Basin0 aBulge Migration and Pinnacle Reef Development Devonian Appalachi  a339-3520 v1083 a<p>Detailed stratigraphic analyses of Late Emsian and Early Eifelian (Lower to Middle Devonian) carbonate‐dominated strata in the northern Appalachian Basin indicate anomalous, locally varying relative sea level changes and inversions of topography. The distribution of a major basal‐bounding unconformity, basinal pinnacle reefs, local absence of parasequences, and eastward migration of shallow marine carbonate lithofacies and related biofacies in the Onondaga Limestone and underlying strata mark the retrograde migration of an elongate, northeast‐southwest‐trending area of positive relief, bordered on its cratonward side by a similarly migrating basin of intermediate depth. These features are thought to represent the forebulge and back‐bulge basin of the Appalachian foreland basin system as it developed during a time of relative quiescence within the Acadian Orogeny. However, the relatively small size of the bulgelike feature (ca. 80–100‐km‐wide, 20–50‐m positive relief), its great distance from the probable deformation front (&gt;400 km), and the lack of a well‐developed foredeep immediately adjacent to the bulgelike feature may indicate that it represents a smaller‐scale flexural high (“flexural welt”) superposed over the cratonward edge of the larger‐scale classical forebulge of the basin. Development of shallow‐water reefs on the crest of the bulge during sea level lowstand, followed by migration of the bulge and widespread transgression, permitted growth of economically significant pinnacle reefs in the deep basin center. Further subsurface reef exploration should concentrate along the projected position of the bulge during the basal Onondaga lowstand.</p>
10acarbonate‐dominated strata10aEarly Eifelian10aLate Emsian10aLower to Middle Devonian10anorthern Appalachian Basin10astratigraphic analyses1 aVer Straeten, C., A.1 aBrett, C.  uhttp://www.jstor.org/stable/10.1086/314402