Ocean Acidification

Highlights

• Peritidal record of the Jenkyns Event.
• Jenkyns Event confirmed with palyno-, chemo and microbiofacies stratigraphy.
• Evidence for subaerial exposure within the NCIE interval.
• Peritidal carbonate factory of the AdCP remained resilient in the Jenkyns Event.
• Local synsedimentary tectonics and eustatic changes superimposed on global trends.

Abstract

Early Jurassic (late Pliensbachian–early Toarcian) Large Igneous Province (LIP) magmatism affected the entire ocean-atmosphere system culminating in a cascade of paleoenvironmental perturbations known as the Jenkyns Event which globally impacted marine, transitional and terrestrial paleoenvironments. Carbonate platforms at low latitudes in the Western Tethys realm drowned or shifted to non-skeletal production during the early Toarcian due to sea level rise, global warming, and ocean acidification. Unlike deep-marine deposits, shallow-marine carbonates present a challenge in defining global geochemical signals due to common diagenetic modifications. An integrated dataset including δ¹³C_carb and δ¹⁸O_carb, TOC, biomicrofacies, SEM, XRD, and palynological study of two stratigraphic successions in the Plitvice Lake region, Bjelopolje (BJ) and Plitvice Spring (PS), in Croatia, provides an overview of the paleoenvironmental evolution and lateral facies changes in a peritidal setting during the Early Jurassic on the Adriatic Carbonate Platform (AdCP). The investigated stratigraphic succession starts with upper Pliensbachian, peloid-ooid-bioclastic grainstones alternating with fenestral and massive mudstones overlain by lower Toarcian, lagoonal, bioturbated, “spotted” limestones with horizons indicative of short-lived subaerial emergence during the early Toarcian. A negative excursion in δ¹³C_carb, foraminifer assemblages, and the predominance of Classopollis pollen within the “spotted” limestones marks the stratigraphic position of the Jenkyns Event. Global-scale events (sea level variation, climate change, C-cycle perturbation, anoxia) operated simultaneously with local to regional synsedimentary tectonics and eustatic movements that preserved the AdCP carbonate factory from collapse or drowning but resulted in pronounced facies differentiation on the shallow-marine carbonate platforms.

Brčić V., Baranyi V., Glumac B., Špelić M., Fuček L., Kukoč D., Petrinjak K., Mišur I., Budić M., Palenik D., Belić N., Kamenski A., Lazar J. M., Šuica S., Grizelj A., Ciglenečki I. & Dautović J., 2024. Impact of the Jenkyns Event on shallow-marine carbonates and coeval emerged paleoenvironments (the Plitvice Lakes region, Croatia). Palaeogeography, Palaeoclimatology, Palaeoecology: 112519. doi: 10.1016/j.palaeo.2024.112519. Article (subscription required).