Fields of study

The early Toarcian (Early Jurassic) of Gondwana was a time of voluminous mafic volcanism that caused major global environmental perturbations (e.g., Burgess et al., 2015, Moulin et al., 2017). Much effort has been made to temporally constrain the timing and rates of volcanic outpouring, magmatic intrusion into organic-rich sedimentary layers, and the resultant early Toarcian global mass extinction (Svenson et al., 2012; Sell et al., 2014; Corfu et al., 2016). The immense and sudden spike in green-house gasses injected into the atmosphere during volcanism of the Karoo-Ferrar Large Igneous Province (LIP) due to the combustion of organic-rich crustal layers in the Karoo Basin (Aarnes et al., 2011) are cited as the main cause The early Toarcian (Early Jurassic) of Gondwana was a time of voluminous mafic volcanism that caused major global environmental perturbations (e.g., Burgess et al., 2015, Moulin et al., 2017). Much effort has been made to temporally constrain the timing and rates of volcanic outpouring, magmatic intrusion into organic-rich sedimentary layers, and the resultant early Toarcian global mass extinction (Svenson et al., 2012; Sell et al., 2014; Corfu et al., 2016). The immense and sudden spike in green-house gasses injected into the atmosphere during volcanism of the Karoo-Ferrar Large Igneous Province (LIP) due to the combustion of organic-rich crustal layers in the Karoo Basin (Aarnes et al., 2011) are cited as the main cause of global climate change and subsequent environmental degradation, especially recorded in the world oceans (Burgess et al., 2015). However, until recently, less effort has been placed on understanding the environments immediately at the site of this intense volcanism. Recent valuable studies focusing on the rare sedimentary interbeds within the basalt-dominated Drakensberg Group (Karoo Supergroup), have provided a glimpse into the challenging conditions for life during and at the locus of continental flood volcanism (e.g., Bordy et al., 2020; Bordy et al., 2021; Bordy et al., 2022). These studies, utilizing macro-scale observations of sedimentary facies, trace-fossils, and fossils, show that life was opportunistic and occupied continental environmental niches that had abundant water but were actively being engulfed, displaced, and destroyed by progressive volcanism. These studies not only contribute towards understanding the southern African fossil record and conditions during the early Toarcian mass extinction, but also have wide implications for most Phanerozoic mass extinction events, since their distribution through time is largely a function of LIP emplacement as continental flood basalts (e.g., Courtillot and Renne, 2003). However, these studies of the sedimentary interbeds in the Drakensberg Group lack the paleoclimatic environmental constraints that offered by microscopic observations of aqueous life at the time. This study investigates a rare limestone interbed within the Drakensberg Group, representing a lacustrine ecosystem on an Early Jurassic volcanic landscape that existed precisely in the wrong place at the wrong time: With a front row seat witnessing the rapid, unbridled outpouring of continental-scale basaltic lava that would dramatically affect life on earth with catastrophic consequences.