Research conducted on carbonate mineral formations has uncovered possible glendonite mineral pseudomorphs, offering new insights related to the end-Permian extinction, which marks the most significant extinction event of the Phanerozoic era. These pseudomorphs, identified on the Arabian Plateau of Oman, suggest unusual oceanic conditions immediately following this catastrophic biotic crisis.
Glendonites, which crystallize from the mineral ikaite, have been traditionally associated with cold marine waters and have been viewed as indicators of low seawater temperatures. These carbonate minerals typically precipitate at low temperatures (−2 to 7°C) through geochemical processes involving the reduction of sulfate either from organic material or methane. While glendonites have primarily been reported from high-latitude environments, this new study indicates their presence as possible pseudomorphs found within subtropical marine carbonates dating back roughly 252 million years.
The research team conducted extensive fieldwork on the Saiq Formation, which reveals alternating sedimentary deposits characterized by marine carbonates and associated geochemical signatures. The sedimentological characteristics suggest these glendonites formed under syn-depositional conditions, either on bedding planes or reworked within sedimentary structures. The carbonate crystals display small, stellate shapes resembling traditional glendonites, with comprehensive examinations reporting unique internal structures.
Stable isotope analyses of the pseudomorphs revealed carbon isotopic values between −0.14‰ and −0.85‰, which differ markedly from typical values found in authentic glendonites. The study concluded these pseudomorphs likely originated from oceanic dissolved inorganic carbon rather than from organotrophic or methanogenic sources commonly associated with traditional glendonites. This findings raises questions about the broader carbon cycling dynamics and environmental changes during and after the end-Permian extinction event.
Such elevated alkalinity and the pH levels above 9 inferred during this time period contributed to the precipitation of these carbonate minerals, linked to significant disruptions within the marine carbon system. The study posits these conditions could have led to the formation of ikaite and its subsequent transformation to glendonites, supporting the notion of altered oceanic conditions immediately following the extinction event.
Further investigations suggest these pseudomorphs may have been influenced by cold bottom water currents, potentially signalling upwelling events of nutrient-rich, cold ocean waters. The presence of these formations may indicate intermittent cold snaps during the early Triassic, as global temperatures surged to unprecedented levels following the extinction.
These findings highlight the complex interaction between biotic crises and geochemical processes, providing evidence of the persistent impact of environmental change. The research emphasizes the need for continued exploration of glendonites and their formation processes to unravel the intertwined history of the earth's significant extinction events and the ecosystems they affect.