--> Integrated Structural and Stratigraphic Analysis of the Guadalupian Seven Rivers Formation, McKittrick Canyon, New Mexico

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Integrated Structural and Stratigraphic Analysis of the Guadalupian Seven Rivers Formation, McKittrick Canyon, New Mexico

Abstract

Syndepositional to early deformation is recognized as a common process within modern and ancient carbonate platforms. However, the degree to which early faulting and down-to-the-basin tilting affect the final orientation of shelf top strata is not well understood. This ambiguity adds uncertainty to sequence stratigraphic frameworks which often take into account stratal geometries and quantified stratigraphic variables such as progradation/aggradation (P/A) ratios. This study utilizes field data and a lidar-based 3D digital outcrop model (DOM) in order to understand the first order controls on seaward-dipping back reef strata within the Guadalupian Seven Rivers Formation in McKittrick Canyon, NM. Understanding the relative contributions of structural and sedimentological processes to final stratal geometry in carbonate platforms will aid in subsurface reservoir characterization, where stratigraphic frameworks rely heavily on stratal geometries from seismic. Research will focus on constructing a cycle- to cycle-set scale stratigraphic framework which will be used to (1) trace key cycle set boundaries across the outcrop in order to create a detailed quantitative reconstruction of facies dip width distribution and (2) document the effects and timing of faulting and down-to-the-basin tilting by creating cross sections restored to key datums such as accommodation-filled cycle caps. Results from field work and DOM analysis indicate that faults grew syndepositionally with a maximum displacement of up to seven meters during Seven Rivers deposition. Faults are positioned seaward of the antecedent Goat Seep margin, which acted as a fulcrum for deformation of younger back reef strata. Similar deformation features have been documented over terminal shelf margins within the overlying Yates Formation but have not been considered important within the Seven Rivers Formation. Conversely, some geometries have a depositional origin; low curvature, concave upwards benches that thicken seaward are a reliable indicator for the fusilinid-rich outer shelf facies tract. Maximum dip width estimates of this facies tract indicate that it comprises a larger portion (up to 500 m) of the shelf profile within the Seven Rivers relative to the overlying Yates and that the narrowing of the outer shelf through time represents a dynamic sedimentological control on platform morphology and stratal geometry.