Document Type
Article
Publication Date
12-2021
Abstract
Chondrodonta is an opportunistic, oyster-like bivalve, common in shallow-water carbonates of the Cretaceous Tethyan Realm. Despite its high abundance and widespread geographic distribution, the precise relationship between the early Aptian proliferation and environmental perturbations resulting from the Oceanic Anoxic Event 1a (OAE1a), has not been investigated. Stratigraphic and geochemical analyses of the lower Aptian Chondrodonta bedsets within the inner platform limestones of the Apulia Carbonate Platform (Gargano Promontory, southern Italy) are conducted to assess the environmental controls on the Chondrodonta proliferation and its timing and causal relationship to OAE1a. Chondrodonta occurs with sparse to common individuals within requieniid rudist floatstone–rudstones, forms monospecific biostromes during the early phase of stressed environmental conditions and then rapidly disappears at the peak of OAE1a. It proliferates in dysoxic seawater with relatively increased trophic sources, which correlate to increasing nutrient levels in the nearby pelagic realm. Chondrodonta-rich beds are associated worldwide with the onset of OAE1a and occur in a transitional context between a stable and a strongly stressed environment, where the opportunistic behaviour of Chondrodonta is rather efficient. Increasing nutrient load and unstable environmental conditions right below the peak of OAE1a created an environmental ‘window’ favourable for Chondrodonta to proliferate, outplaying the less tolerant benthos (for example, rudists). The occurrence, duration and position of the environmental window were controlled by local palaeogeographic and hydrodynamic settings (i.e. low energy, decreased seawater oxygenation and circulation). Further increase in inhospitable conditions, leading to OAE1a, constituted an upper threshold for Chondrodonta and allowed mesotrophic taxa like Bacinella–Lithocodium and orbitolinids to dominate the benthic communities. The present study suggests that the proliferation of Chondrodonta in shallow-water platform carbonates can be used as proxy for the initial phase of ecological stress related to OAE1a.
Identifier
85108274041 (Scopus)
DOI
10.1111/sed.12887
Publisher
John Wiley & Sons Ltd.
ISSN
00370746
Repository Citation
Del Viscio, G., Frijia, G., Posenato, R., Singh, P., Lehrmann, D. J., Payne, J. L., Al-Ramadan, K., ... & Morsilli, M. (2021). Proliferation of Chondrodonta as a proxy of environmental instability at the onset of OAE1a: Insights from shallow-water limestones of the Apulia Carbonate Platform. Sedimentology, 68(7), 3191-3227. http://doi.org/10.1111/sed.12887
Publication Information
Sedimentology
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.