Onset of the Mid-Cretaceous greenhouse; volcanic events and the biological, sedimentary and geochemical responses

Author(s): Larson, Roger L.; Erba, Elisabetta
Author Affiliation(s): Primary:
University of Rhode Island, Graduate School of Oceanography, Narragensett, RI, United States
Universita di Milano, Italy
Volume Title: Geological Society of America, 1998 annual meeting
Source: Abstracts with Programs - Geological Society of America, 30(7), p.53-54; Geological Society of America, 1998 annual meeting, Toronto, ON, Canada, Oct. 26-29, 1998. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0016-7592 CODEN: GAAPBC
Note: In English
Summary: Radiometrically-dated basalts from Ontong-Java and Manihiki Plateaus in the western Pacific are evidence for the simultaneous formation of these huge features at about 124-122 Ma, although the uppermost basalts and deepest sediments from ODP 807C on Ontong-Java suggest a slightly subsequent, but probably distinctly separate event at about 121-120 Ma. Spreading rates increased between 121. 5 and 83. 5 Ma, although the temporal distribution of the spreading rate increase within this 38-m. y. period is unknown. Several responses to these large volcanic events probably resulted from accelerated hydrothermal processes delivering increased mantle effluents to the oceans. These responses occurred in the following stratigraphic order with the associated, approximate chronological ages, based in part on our redating of the base of the M0 magnetic reversed interval at 122 Ma. Strontium isotope ratios began to decline about 123 Ma. Nannoconid abundances began to decline, and radiolaria, planktonic foraminifera and calcareous nannofloras began to experience fluctuating abundances and speciation about 123-122. 5 Ma. Metal concentrations of Co, Mn, Pb, Yb, and Cu peaked about 122-121. 5 Ma (Duncan et al., 1997). All of these fluctuations preceded an abrupt change in sedimentation from predominately carbonate to a more reduced, organic-carbon regime whose basal member is the Selli black shale event (OAE-1a). Changes in planktonic communities and sedimentation culminated in a nannoconid "crisis" at about 121 Ma and in the Selli black shale at about 121-120 Ma. A large positive excursion of delta Carbon 13 followed the Selli event at about 120-119 Ma and strontium isotope ratios reached minimum values at about 116-113 Ma.These trends may have been accelerated towards their respective extrema by formation of the Nova-Canton Trough rift system at about 123-118 Ma, by smaller volcanic features in the northwestern Pacific that formed between 128-111 Ma, by others that have been subducted, or by still-existing features that have not yet been dated adequately.
Year of Publication: 1998
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Alkaline earth metals; Basalts; Black shale; Carbon; Clastic rocks; Cobalt; Copper; Cretaceous; East Pacific; Foraminifera; Geochemistry; Igneous rocks; Invertebrata; Isotope ratios; Isotopes; Lead; Leg 130; Manganese; Manihiki Plateau; Mesozoic; Metals; Middle Cretaceous; Nannofossils; Nova-Canton Rift; ODP Site 807; Ocean Drilling Program; Ontong Java Plateau; Organic carbon; Pacific Ocean; Paleomagnetism; Plantae; Plate tectonics; Protista; Radiolaria; Rare earths; Rates; Reversals; Rift zones; Sea-floor spreading; Sedimentary rocks; Sedimentation; South Pacific; Southeast Pacific; Sr-87/Sr-86; Stable isotopes; Strontium; Subduction; Volcanic rocks; Volcanism; West Pacific; Ytterbium
Coordinates: N033622 N033626 E1563730 E1563728
Record ID: 1999016142
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