Nd isotopic constraints on sediment sources of the Ouachita-Marathon fold belt

Nd isotopes for the overthrust deep-marine Ouachita-Marathon sedimentary assemblage of Arkansas-Oklahoma and west Texas, and associated Paleozoic shelf and foreland deposits, resolved into three distinct populations: 1) Lower to Middle Ordovician, ε _Nd = -13 to -16 (average T _DM = 2.0 Ga); 2) Upper Ordovician to Pennsylvanian, ε _Nd = -6 to -10 (average T _DM = 1.6 Ga); and 3) Mississippian tuffs, ε _Nd = -1 to -3 (average T _DM = 1.1 Ga). A rapid shift in ε _Nd from -15 (passive margin shales) to -7 (orogenic turbidites) in the Ouachita assemblage at ca. 450 Ma implies termination of craton-dominated sources and the emergence of the Appalachian orogen as the primary source of sediment for sea floor lying south of North America. Nd isotopes in fluvio-deltaic strata of the Ouachita-Appalachian foreland and continental interior, that is, Arkoma, Illinois, and Black Warrior basin (ε _Nd = -7 to -10), imply that continental margin pathways and interior basins received the same detritus as the Ouachita trough by Pennsylvanian time. -from Authors