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<p>The late Cambrian is known for global biogeochemical perturbations to the marine carbonate system whose timing, extent, and duration remain unresolved, highlighting the need for high-resolution facies analyses to assess the nature of carbonate deposition. We investigate the dominant processes contributing to carbonate deposition using lithologic, microfacies, petrographic point count, and stable isotope analyses at a previously undescribed section at Rendezvous Peak, western Wyoming. The lower Pilgrim Limestone of the Gallatin Group represents deposition in an offshore storm-dominated carbonate platform composed of flat pebble conglomerates and laminated glauconitic and micropeloidal carbonate mudstones. Facies shift to middle and platform edge packstone/grainstone units that include two microbialite horizons. The upper Pilgrim Limestone returns to offshore flat pebble conglomerates and laminated micropeloidal carbonate mudstones during the continued interpreted marine transgression. Point count data indicate consistently low skeletal contributions (2.9% <i>− 7</i>.0%), with carbonate deposition dominated by oolitic, microbial, peloidal, and intraclastic grains, suggesting environmental stress on skeletal communities. Carbonate carbon stable isotope values (− 0.60‰ to − 0.19‰; mean = − 0.40‰ ± 0.11‰, <i>n</i> = 31) corroborate the stratigraphic position of the Pilgrim Limestone below the Snowy Range/Open Door Limestone. Together, these results provide a high-resolution record of carbonate factory dynamics and depositional environments immediately preceding late Cambrian global carbon cycle perturbations and associated biotic turnover.</p>

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High-resolution facies analysis of the Upper Cambrian Pilgrim Limestone at Rendezvous Peak, Western Wyoming: Implications for carbonate factory dynamics and lithostratigraphic correlation

  • 期刊论文

  • 发表日期：

    2026年8月3日

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  • Sonicah Sanon,
  • Oscar Munoz,
  • Yadira Ibarra

摘要

The late Cambrian is known for global biogeochemical perturbations to the marine carbonate system whose timing, extent, and duration remain unresolved, highlighting the need for high-resolution facies analyses to assess the nature of carbonate deposition. We investigate the dominant processes contributing to carbonate deposition using lithologic, microfacies, petrographic point count, and stable isotope analyses at a previously undescribed section at Rendezvous Peak, western Wyoming. The lower Pilgrim Limestone of the Gallatin Group represents deposition in an offshore storm-dominated carbonate platform composed of flat pebble conglomerates and laminated glauconitic and micropeloidal carbonate mudstones. Facies shift to middle and platform edge packstone/grainstone units that include two microbialite horizons. The upper Pilgrim Limestone returns to offshore flat pebble conglomerates and laminated micropeloidal carbonate mudstones during the continued interpreted marine transgression. Point count data indicate consistently low skeletal contributions (2.9% − 7.0%), with carbonate deposition dominated by oolitic, microbial, peloidal, and intraclastic grains, suggesting environmental stress on skeletal communities. Carbonate carbon stable isotope values (− 0.60‰ to − 0.19‰; mean = − 0.40‰ ± 0.11‰, n = 31) corroborate the stratigraphic position of the Pilgrim Limestone below the Snowy Range/Open Door Limestone. Together, these results provide a high-resolution record of carbonate factory dynamics and depositional environments immediately preceding late Cambrian global carbon cycle perturbations and associated biotic turnover.