MOROCCO AS A REFUGIA FOR BENTHIC MACROFAUNAL COMMUNITIES DURING THE EARLY JURASSIC CLIMATE CRISES

The Pliensbachian/Toarcian boundary event (~184.2 million years ago) and the Toarcian Oceanic Anoxic Event (TOAE, ~183 million years ago) represent two of the most severe environmental perturbations of the Early Jurassic Epoch, leading to global marine ecosystem disruption and biotic crises. Previous work on these crises has implicated warming-induced anoxia as the primary driver for the extinctions. Recent studies, however, show elevated extinction rates in well-oxygenated basins, such as the Lusitanian Basin in Portugal, the Iberian Basin in Spain, and the High Atlas Basin in Morocco. Furthermore, subtle differences in environmental conditions (such as, warming or eutrophication) between the two events have been identified at multiple localities. This research will quantitatively evaluate the macrobenthic communities through this interval in order to determine how these communities responded to the two Early Jurassic events. In our current study, we use basin-wide sequence stratigraphy to correlate the occurrence, abundance, and diversity of the level-bottom communities (e.g., bivalves, brachiopods) across multiple sections in the Central High Atlas Basin of Morocco. Our data shows the Pliensbachian/Toarcian boundary event or the Toarcian event have no significant impact on the diversity of the Moroccan level bottom communities during the studied interval. There was no significant loss of taxonomic diversity or functional groups across the two events, instead there was a diversification amongst the macrofaunal communities after the Toarcian event. We hypothesize the Central High Atlas Basin was a refugia for macrofaunal communities. Comparable data from other localities across the two Early Jurassic events reports severe biotic crises both from the deeper-water, extratropical shales as well as from tropical carbonate depositional settings. Therefore, the new macrofaunal data from tropical, shallow-water sections in Morocco are critical to our understanding of organism survival during the severe Early Jurassic climate crises.