High-frequency sequence stratigraphy of Pennsylvanian-Lower Permian carbonate successions of the Robledo Mountains, New Mexico and the Carnic Alps, Austria: a record of the acme and demise of the late Palaeozoic ice age

The cyclic to non-cyclic Pennsylvanian-Lower Permian successions of the Robledo Mountains, New Mexico and the Carnic Alps, south Austria, record the acme and demise of the late Palaeozoic ice age (LPIA). Microfacies analyses of cyclic strata of the Pennsylvanian-Asselian Horquilla, Shalem Colony (New Mexico), and Schulterkofel (Carnic Alps) formations record glacioeustatic sea-level fluctuations of an amplitude on the order of 100 m. These fluctuations were the result of Milankovitch-driven eustatic sea-level shifts associated with the waxing and waning of ice sheets during the peak of the main phase of the LPIA. Microfacies analyses of the overlying upper Asselian cyclothems of the Community Pit, Robledo Mountains (New Mexico) and Zweikofel (Carnic Alps) formations record relatively moderate sea-level variations on the order of a few tens of metres (~ 30–40 m). This comparatively minor sea-level amplitude may be linked to the demise of ice sheets during the final stages of the LPIA and the limited input that shrinking ice sheets had on global sea-level fluctuations prior to their final collapse at the Asselian-Sakmarian boundary. The uppermost part of the Robledo Mountains and the Apache Dam (New Mexico) and Zottachkopf (Carnic Alps) formations are Sakmarian. These strata are interpreted as non-cyclic and represent sedimentation following the end of the LPIA.