TY  - JOUR
A1  - Frijia, Gianluca
A1  - Forkner, R.
A1  - Minisini, D.
A1  - Pacton, M.
A1  - Struck, Ulrich
A1  - Mutti, Maria
T1  - Cyanobacteria proliferation in the cenomanian-turonian boundary interval of the apennine carbonate platform:
BT  - immediate response to the environmental perturbations associated with OAE-2?
JF  - Geochemistry, geophysics, geosystems
N2  - Oceanic Anoxic Event-2 (OAE-2; Cenomanian-Turonian) is characterized by extensive deposition of organic carbon-rich deposits (black shales) in ocean basins worldwide as result of a major perturbation of the global carbon cycle. While the sedimentological, geochemical, and paleontological aspects of deep water expressions of OAE-2 have been intensively studied in the last few decades, much less attention has been given to the coeval shallow water deposits. In this study, we present the results of a detailed facies and petrographic (optical microscope and scanning electron microscopy) and geochemical studies (delta C-13(carb), delta C-13 (org), delta N-15(bulk), TOC, and Rock-Eval pyrolysis) on two key shallow marine sections from the Apennine Carbonate Platform (ACP; Italy). Here a continuous record of shallow water carbonates through the OAE-2 interval is preserved, offering the unique opportunity to document the archive of paleoenvironmental changes in a neritic setting, at a tropical latitude and far from the influence of a large continental block. Two conspicuous intervals are characterized by abundant and closely spaced dark microbial laminites found at correlative stratigraphic horizons in the two stratigraphic sections. These laminites contain elevated concentrations of TOC (up to 1%) relative to microbial capping cycles laminites stratigraphically above and below. The organic matter preserved in these fine-grained laminites is dominated by cyanobacteria remains, which accounted for most of the organic matter produced on the ACP in these intervals. Our study suggests that Tethyan carbonate platforms experienced significant biological changes during OAE-2, alternating, in few kiloyears, between eutrophic phases dominated by microbial communities and mesotrophic/oligotrophic conditions favoring normal carbonate production/sedimentation. The synchronous occurrence of microbialite facies at different locations across the ACP and on other platforms worldwide (e.g., Mexico and Croatia) suggests a causal link between Large Igneous Province volcanism and the environmental conditions necessary to trigger cyanobacterial proliferation on shallow carbonate platforms.
KW  - OAE-2
KW  - Apennine Carbonate Platform (ACP)
KW  - Cyanobacteria
KW  - C isotopes
KW  - N isotopes
Y1  - 2019
U6  - https://doi.org/10.1029/2019GC008306
SN  - 1525-2027
VL  - 20
IS  - 6
SP  - 2698
EP  - 2716
PB  - American Geophysical Union
CY  - Washington
ER  -