WHAT IS THE EXTENT OF 1.1 GA AND CAMBRIAN RIFTING IN SOUTHERN LAURENTIA?

With the USArray component of EarthScope moving eastward, the middle of the country will soon be the focus of many member of the geoscience community. In addition to many older Precambrian features, this region contains two globally significant features, the Mid-Continent rift system and the Southern Oklahoma aulacogen. The Mid-Continent rift is traditionally viewed as ending in central Kansas and the Southern Oklahoma aulacogen can be interpreted as ending in the Texas Panhandle. However, we have employed new data and public domain compilations of gravity and aeromagnetic data for the U. S. to construct a series of maps using variety of digital filtering techniques in order to better delineate anomalies and interpret regional-scale structures. Techniques applied in this analysis include reduction to pole for magnetic data, upward continuation and subtraction to yield residual maps of gravity anomalies, as well as, band-pass and directional filtering. As expected, the Mid-continent rift zone is the dominant feature on in the northern portion of these maps. However, there is also significant basement texture that is not a product of this rift. This texture is partially concealed by the overwhelming anomalies associated with the Mid-Continent rift and related features. Directional filtering, however, allows the northeast-trending structures associated with the rift to be subdued or removed from the maps, which facilitates the study of anomalies due to basement textures resultant from other tectonic events. It appears possible that the Mid-Continent rift could extend further southward beneath the much younger Anadarko basin of Oklahoma and abut the Southern Oklahoma aulacogen (SOA). In the south, the SOA and the rifted margin of Laurentia produce equally dominant geophysical signatures. We have applied similar digital processing techniques to investigate the extent of Cambrian rifting. A picture is emerging in which the SOA fans out as it extends northwestward from the Texas Panhandle in a similar fashion to the way the Kenya fans out southward into Tanzania. EarthScope data will soon be providing badly needed data on the deep structure of these features that well provide new information on how they have modified the lithospheric structure of the region.