GSA Connects 2021 in Portland, Oregon

Paper No. 122-11
Presentation Time: 2:30 PM-6:30 PM


STONE, Travis1, MARTINDALE, Rowan2, FONVILLE, Tanner1, BODIN, Stéphane3, VASSEUR, Raphäel4, LATHUILIÈRE, Bernard4 and KABIRI, Lahcen5, (1)Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, 2305 Speedway, Stop C1160, Austin, TX 78712-1692, (2)Jackson School of Geosciences, University of Texas at Austin, 1 University Station C1100, Austin, TX 78712, (3)Department of Geoscience, Aarhus University, Aarhus, Denmark, (4)University of Lorraine, Nancy, 54 042, France, (5)Department of Geological Sciences, University Moulay Ismail, Errachidia, Morocco

The Early Jurassic was a tumultuous time for reef ecosystems, with multi-phased extinctions at the Pliensbachian/Toarcian (Pl/To) boundary event and the Toarcian Oceanic Anoxic event (T-OAE). Excellent Lower Jurassic reef deposits occur in the Central High Atlas region of Morocco, where changes in reef communities can be assessed in the context of the Pl/To and T-OAE. Analyses of the changes in reef architecture and fauna provide insight into how the environmental stresses associated with each extinction event (i.e., ocean acidification and ocean warming) impacted these ecosystems. Although these events resulted in catastrophic extinctions for the main reef builders (corals and lithiotid bivalves), reef recovery occurred unusually quickly; therefore, an assessment of reef communities in the wake of each event, which documents how new faunas filled critical reef niches, may provide insight into the cause of the accelerated recovery.

The faunal and structural differences between early Pliensbachian, late Pliensbachian, earliest Toarcian, and post-T-OAE reefs in this region are not currently well known, so reefs at each interval will be described. Specifically, we will be assessing their structural and compositional characteristics (i.e., framework and interstitial component percentage and composition, similarity profiles) and comparing them to one another using ecological metrics (i.e., abundance, diversity, evenness, and richness). This poster will describe preliminary field observations of these reef ecosystems as well as microfacies analyses of samples from the early and late Pliensbachian reefs (point counts of taxa, taxa ID, structural percentage of the reefs, and differences in reef facies). Analyses of these deposits will allow us to understand what environmental conditions led to the Early Jurassic extinctions in reef ecosystems, how the structure of reefs changed following these events, why certain taxa survived while others did not, and what conditions led to reef recovery. An understanding of how reefs responded to and recovered from these Jurassic events may inform conservation tactics for modern communities or may inform reef studies during other extinctions.