OVERVIEW OF THE SOUTHERN OKLAHOMA AULACOGEN

The Southern Oklahoma Aulacogen (SOA) represents the last magmatic episode of the crustal block known as Laurentia. Understanding its magmatic/tectonic history, and the origin of its rocks, may contribute to an understanding of the formation of other rifts which have cut Laurentia and the nature of the subjacent mantle. Some key points: 1)Age, as dated by its exposed parts, is 530-540Ma, near the Proterozoic-Cambrian boundary. 2)The SOA now is a fin of mantle-derived material cross-cutting presumed older Granite-Rhyolite crust. 3)The SOA represented an intimate connection between magmatism and extensional tectonism. 4)The exposed silicic parts represent the top of the rift sequence. Most of the buried SOA additions to the crust are mafic. 5)The extent of the SOA is outlined in the positive Bouguer gravity anomaly in the regional gravity field. 6)The SE end of the SOA marks the southern edge of Laurentia. 7)The SOA crustal section behaved mechanically as a unit in subsequent tectonism, dismembering the ancestral Anadarko (Oklahoma) Basin during the Pennsylvanian Ouachita orogeny.

The relations known and reasonably inferred for this rift may be used as a reference for comparing other buried and less completely exposed rifts of southern Laurentia.