Geochemical analysis of mass mortality events in the Cretaceous (Aptian) Konservatt-Lagerstätte of Crato paleolake, Brazil

• Published in: Palaeogeography, palaeoclimatology, palaeoecology palaeoclimatology, palaeoecology, 2024-12, Vol.655, p.112558, Article 112558
• Main Authors: Hamid, Igor, Martins, Mariana Silvestre, Saraiva, Antônio Álamo Feitosa, Benigno, Ana Paula Aquino, de Lima, Flaviana Jorge, Bantim, Renan Alfredo Machado, Sial, Alcides Nobrega, Aguiar, José Edvar, Duong, Minh Thao Nguyen, Dang, Duc Huy, de Lacerda, Luiz Drude
• Format: Article
• Language: English
• Subjects: Enrichment factor; Metals; Paleoclimatic changes; Volcanism; Water level
• ISSN: 0031-0182
• DOI: 10.1016/j.palaeo.2024.112558

Geochemical records from the Cretaceous (Aptian) Crato paleolake in Brazil reveal the influence of volcanism and wet-dry paleoclimatic variations on the lake system and improve understanding of the mass mortalities represented by Konservat-Laggerstätte assemblages in the deposits. Specifically, we used paleoredox (PbEF, MnEF, UEF, VEF, MoEF, FeEF, V/Cr and U/Th ratios) and paleoproductivity (PEF, CuEF, ZnEF, NiEF, BaEF, and δ13CVPDB) indexes to elucidate changes in detrital input (Al and Fe), paleoclimate (Sr/Cu, C- values, Sr/Al and Mg/Al), paleosalinity (Sr/Ba and Rb/K), and lake level (Fe/Mn and δ18OVPDB), and their linkage to episodes of volcanism (Hg/Al and Hg/Fe). The mass mortalities of lacustrine organisms are found to be closely related to paleoclimatic variations. During dry episodes, the lake became more saline and alkaline, which impeded the larval development and the maturation of mayflies (Ephemeroptera), and triggered mass mortality events of these organisms. During wet periods, metal enrichment indicates that a rise in paleoproductivity may have caused hypoxia, thereby inducing the mass mortality events among Dastilbe fish. Mercury anomalies suggest that extrusion of Rajmahal-Kerguelen Plateau basalts in the late Aptian times influenced regional paleoclimatic and depositional processes, and may have been ultimately responsible for generating the Konservat-Lagerstätte of the Crato paleolake. [Display omitted] •Mass mortality events in the Konservat-Lagerstätte of the Crato paleolake were caused by high productivity and anoxia.•Stable isotopes (δ13CVPDB and δ18OVPDB) and trace metal enrichment were consistent proxies of paleoenvironmental changes.•Hg anomalies indicated the paleoenvironmental changes in the Crato paleolake were a consequence of LIP activation.