NORTHEAST-TRENDING BASEMENT ZONES SEGMENT FLEXURAL NORMAL FAULTS OF THE ARKOMA BASIN: EVIDENCE FROM BASIN-SCALE 3D MODELING

Extensional faults are key components of foreland basin systems. They form within the upper crust in response to flexure of the lithosphere and accommodate subsidence within the foredeep and forebulge depozones. Such faults are excellent proxies for orogenic system evolution and control the distribution of natural resources and hazards. However, flexural extensional faults are not often well-documented at a basin-scale, thereby limiting our understanding of the distribution of slip, fault pattern controls, and the relation between those patterns and the basin system as a whole.

Here, we present high-resolution 3D modeling of the northern Arkoma Basin and southern Ozark Dome in Arkansas. We synthesize a large database of previous geologic mapping, existing research, subsurface formation tops, and high-resolution magnetic data into 3D geologic and 2D kinematic models. Mesh surfaces representing several key stratigraphic horizons of Carboniferous time (ca. 335-306 Ma) were constructed. The mesh surfaces are offset by a complex 3D fault network, allowing detailed analysis of along-strike and down-dip variations in fault displacement.

Analysis of the 3D model reveals a regular and repeated fault segmentation pattern wherein E-W striking, left-stepping en échelon normal faults are segmented by inherited NE-striking basement faults related to the late Precambrian Reelfoot Rift. Maximum vertical separation along the E-W normal faults is generally focused between the inherited NE-trending basement structures. This supports the hypothesis that the inherited basement faults delocalized extensional strain during late Paleozoic normal faulting. The NE-trending basement faults also segment the major natural gas reservoirs of the basin, which are hosted in anticlines and duplex structures. The E-W normal faults buttressed the orogenic wedge, promoting duplex formation and localizing fault bend folds.