TY - JOUR

T1 - Fossil-Bearing Concretions of the Araripe Basin Accumulated During Oceanic Anoxic Event 1b

AU - Bom, M. H.H.

AU - Kochhann, K. G.D.

AU - Heimhofer, U.

AU - Mota, M. A.L.

AU - Guerra, R. M.

AU - Simões, M. G.

AU - Krahl, G.

AU - Meirelles, V.

AU - Ceolin, D.

AU - Fürsich, F.

AU - Lima, F. H.O.

AU - Fauth, G.

AU - Assine, M. L.

N1 - Funding Information: The authors thank the Brazilian Petroleum Company (PETROBRAS) and the Brazilian National Petroleum Agency (ANP) for financial support within the Mar Interior project (SAP4600595925, 5900.0112728.19.9), L.M.A and M.S thanks the São Paulo State Research Foundation, FAPESP (Grants 2004/15786‐0; 2014/27337‐8), and the National Research Council, CNPq, Brazil, (Grant 401039/2014‐5) for the financial support. U.H. thanks the financial support from the German Research Foundation (DFG) project HE 4467/1‐1 (UH). G.F. is grateful to CNPq for the Grant 308087/2019‐4. M.H.H.B. is CAPES fellow. We thank to technical staff at Technological Institute for Paleoceanography and Climate Changes (itt OCEANEON–UNISINOS) for assistance. Finally, helpful comments by two anonymous reviewers helped us to improve the first version of the manuscript.

PY - 2023/11/21

Y1 - 2023/11/21

N2 - Fossils from the Araripe Basin (northeastern Brazil) are known for their remarkable preservation of vertebrates and invertebrates, even including soft tissues. They occur in carbonate concretions within organic carbon-rich strata assigned to the Romualdo Formation. Here we present integrated stable isotope, elemental and microfossil records from the Sítio Sobradinho outcrop, Araripe Basin, northeastern Brazil. Our results imply that black shales hosting fossil-bearing carbonate concretions within the lower Romualdo Formation were deposited during Oceanic Anoxic Event (OAE) 1b (Kilian sub-event). Our high-resolution multi-proxy approach allows identifying four phases of environmental evolution. After a pre-event phase, an early phase (onset of the negative carbon isotope excursion—nCIE) of water column stratification and reduced oxygenation likely preconditioned the system for organic carbon burial and preservation. A second phase (peak nCIE) was characterized by an intensified hydrological cycle and continental runoff, as well as increased influx of terrestrial organic matter. High input of continent-derived nutrients might have enhanced biological productivity in the epicontinental sea, ultimately leading to increased organic carbon fluxes and burial, as well as carbonate dissolution at the seafloor. All together, these paleoenvironmental conditions resulted in expansion of an oxygen minimum zone (OMZ), favoring taphonomic processes that led to the excellent preservation of diverse macro- and microfossils. The nCIE recovery phase was characterized by reduced nutrient supply and organic carbon burial. Organic carbon sequestration in such paleoenvironments likely contributed to the recovery (increase) of stable carbon isotope (δ13C) records in the deep ocean during the Kilian sub-event of OAE 1b.

AB - Fossils from the Araripe Basin (northeastern Brazil) are known for their remarkable preservation of vertebrates and invertebrates, even including soft tissues. They occur in carbonate concretions within organic carbon-rich strata assigned to the Romualdo Formation. Here we present integrated stable isotope, elemental and microfossil records from the Sítio Sobradinho outcrop, Araripe Basin, northeastern Brazil. Our results imply that black shales hosting fossil-bearing carbonate concretions within the lower Romualdo Formation were deposited during Oceanic Anoxic Event (OAE) 1b (Kilian sub-event). Our high-resolution multi-proxy approach allows identifying four phases of environmental evolution. After a pre-event phase, an early phase (onset of the negative carbon isotope excursion—nCIE) of water column stratification and reduced oxygenation likely preconditioned the system for organic carbon burial and preservation. A second phase (peak nCIE) was characterized by an intensified hydrological cycle and continental runoff, as well as increased influx of terrestrial organic matter. High input of continent-derived nutrients might have enhanced biological productivity in the epicontinental sea, ultimately leading to increased organic carbon fluxes and burial, as well as carbonate dissolution at the seafloor. All together, these paleoenvironmental conditions resulted in expansion of an oxygen minimum zone (OMZ), favoring taphonomic processes that led to the excellent preservation of diverse macro- and microfossils. The nCIE recovery phase was characterized by reduced nutrient supply and organic carbon burial. Organic carbon sequestration in such paleoenvironments likely contributed to the recovery (increase) of stable carbon isotope (δ13C) records in the deep ocean during the Kilian sub-event of OAE 1b.

KW - Aptian-Albian

KW - carbonate concretions

KW - Cretaceous

KW - Kilian subevent

KW - Romualdo formation

UR - http://www.scopus.com/inward/record.url?scp=85177457012&partnerID=8YFLogxK

U2 - 10.1029/2023PA004736

DO - 10.1029/2023PA004736

M3 - Article

AN - SCOPUS:85177457012

VL - 38

JO - Paleoceanography and Paleoclimatology

JF - Paleoceanography and Paleoclimatology

SN - 2572-4517

IS - 11

M1 - e2023PA004736

ER -