High-resolution sequence stratigraphy of the Upper Ordovician Montoya Group, southern New Mexico and western Texas: Outcrop analog of an unconventional chert and carbonate reservoir

Abstract

The Upper Ordovician Montoya Group crops out in southern New Mexico and westernmost Texas and records predominantly subtidal deposition on a gently dipping carbonate ramp that was subsequently almost entirely dolomitized. The Montoya Group is a third-order composite sequence composed of six regionally correlative, shallowing-upward, third-order depositional sequences (M0-M5). Sequence M0 has sandstone at its base that is overlain by skeletal packstone-grainstone. Sequence M0 occurs only locally and was likely deposited in a topographic low formed during regional development of the unconformity following El Paso Group deposition. Sequence M1, marking the initial widespread transgression over the Ellenburger unconformity, consists of sandstone updip that passes downramp into skeletal packstone. The highstand systems tract (HST) of M1 consists of a prograding skeletal grainstone that was subaerially exposed upramp. Sequence M2, which contains the second-order maximum flooding surface, has abundant subtidal cherty carbonate at its base, which shallows upward into a widespread, prograding coral packstone-grainstone in the HST. Sequence M3 also contains abundant downramp chert that passes upramp into an aggrading crinoidal shoal and farther upramp into peritidal mudstone. Sequence M4 records an extensive basinward shift in facies as peritidal burrowed and cryptalgalaminated mudstone prograded over subtidal

Role of Deep Fluid Injection in Induced Seismicity in the Delaware Basin, West Texas and Southeast New Mexico

“…Late Ordovician and Early Silurian deposition on the shallow-water platform, including that of the Montoya Group and Fusselman Formation, was dominated by carbonates with local terrigenous clastics sourced from highlands in present-day northern NM (Harrington & Ruppel, 2019). Based on cores and cuttings (Harrington & Ruppel, 2019;Thomas & Liu, 2003), outcrops (Howe, 1959;Pope, 2004Pope, , 2014, and subsurface studies (Ball, 2003;Behnken, 2003), Montoya Group lithology is interpreted as dolomitic in the northern part of the basin and cherty in the more distal parts of the basin to the south, with prevalent limestone elsewhere (Harrington & Ruppel, 2019). The Fusselman Formation represents the continued development of this (Ewing, 1991), basement-rooted faults (Horne et al, 2021(Horne et al, , 2024 and shallow faults (Horne et al, 2022) shallow-water platform and consists of carbonate facies that reflect the generally east-west trending platform margin (Canter et al, 1992) with shallower shelf conditions to the north.…”