Upper Aptian-lower albian seawater composition and OAEs: Geochemistry of Agua Salada and Lampazos Formations, Sonora, Mexico. (August 2021)

• Record Type: Journal Article
• Authors: Saucedo-Samaniego, J.C.; Madhavaraju, J.; Sial, Alcides N.; Monreal, R.; Scott, Robert W.; Perez-Arvizu, O.
• Is Part Of: Journal of South American earth sciences. Volume 109(2021)
• Publication Date: 2021-08
• Subjects: Limestone -- Rare earth elements -- Carbon isotope chemostratigraphy -- Aptian-albian -- OAE 1b; Geology -- Latin America -- Periodicals; Earth sciences -- Latin America -- Periodicals; Geology -- Antarctica -- Periodicals; Earth sciences -- Antarctica -- Periodicals; Geology -- Caribbean Area -- Periodicals; Earth sciences -- Caribbean Area -- Periodicals; Géologie -- Amérique latine -- Périodiques; Sciences de la terre -- Amérique latine -- Périodiques; Géologie -- Antarctique -- Périodiques; Sciences de la terre -- Antarctique -- Périodiques; Géologie -- Caraïbes (Région) -- Périodiques; Sciences de la terre -- Caraïbes (Région) -- Périodiques; Earth sciences; Geology; Antarctica; Caribbean Area; Latin America; Periodicals; 550.5
• DOI: 10.1016/j.jsames.2021.103193
• Languages: English
• ISSNs: 0895-9811

Abstract

Abstract: Upper Aptian-lower Albian seawater composition changes and redox conditions in limestones of the Agua Salada and Lampazos formations in Mexico were investigated by data of major oxides, trace elements, rare-earth elements, and stable isotopes. Most limestones of the Agua Salada Formation (Group 1) show REE + Y patterns consistent with precipitation from seawater whereas limestones from the upper part of the Agua Salada and Lampazos formations (Group 2) have non-seawater-like REE + Y patterns. The relationship among REE and major and trace elements indicates that contamination by detrital input is the main source of REEs, followed by Fe-oxyhydroxides. The variations in Ce anomalies were influenced by paleo-redox conditions. The carbon isotope values, low Mn/Sr ratio and absence of correlation between δ 13 C vs δ 18 O values suggest that δ 13 C retained its original marine signatures during diagenesis. The δ 13 C curve has several significant negative isotopic excursions in upper Aptian-lower Albian strata. The variations in δ 13 C values and their negative excursions, fossil evidence, positions of δ 13 C segments, and correlation of this curve with global reference curves permits documentation of OAE 1 b and the associated sub-events such as Jacob, Kilian, Paquier and Leenhardt sub-events. Highlights: The Group 1 limestones show seawater-like-REE+Y patterns and Group 2 limestones have non-seawater-like-REE+Y patterns. The variations in Ce anomalies were likely influenced by paleoredox conditions. The Aptian-Albian boundary is placed few meters above the base of the Lampazos Formation at the first occurrence (FO) of Colomiella tunisiana . Fossil evidence and positions of d 13 C segments permit documentation of OAE 1b and the associated sub-events.