DETRITAL ZIRCONS AND SEDIMENT ROUTING IN THE YOUNGEST ROCKS OF THE ARKOMA BASIN FILL IN ARKANSAS, USA

Desmoinesian sediments of the Boggy Formation are the youngest Paleozoic rocks of the Arkoma Basin in Arkansas. These rocks are the last preserved record of the Arkoma basin fill and reveal insight into sediment routing and uplift history of the Ouachita Mountains during the suture between Laurentia and Gondwana.

We document changes in sedimentation in response to the development of the collision between Laurentia and Gondwana leading up to the Desmonian strata in the Atoka, Hartshorne, McAlester, Savanna and finally Boggy Formations. These formations comprise laterally correlative sandstones, shales, coalbeds, and occasional limestones, interpreted to represent changing depositional environments between shallow marine to deltaic, paludal, and fluvial facies. Regional correlations were constructed based on new geologic mapping and existing geologic studies across the Arkoma Basin from Arkansas to the type sections in Oklahoma, an approximately 150 km transect. High-resolution LIDAR data was integrated with mapping and a local measured section was constructed on Mount Magazine, in the center of the basin. Paleoflow directions were compiled from existing publications and new mapping indicating general basin-axial flow.

Preliminary detrital zircon U-Pb data collected in the Boggy Formation show a distinctive Paleoproterozoic source of approximately ~2.1 Ga, and Neoproterozoic grains of ~0.55 – 0.7 Ga. These age modes are in contrast with samples from the underlying Savanna and older formations nearby, which show signals corresponding with typical Laurentian sources. From other studies, only the Late Mississippian Stanley Formation from the southern Ouachita Mountains shows a similar provenance.

These data suggest drainage reorganization from dominantly northeastern sediment sources on the Laurentian continent to a mixture of northern and southern sources in the Boggy Formation, indicating a major shift in sediment that accessed (peri-)Gondwanan terranes at this time.