A review of calcareous nannofossil changes during the early Aptian oceanic anoxic event 1a and the Paleocene-Eocene thermal maximum; the influence of fertility, temperature, and pCO2

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doi: 10.11330/2007.2424(05)
Author(s): Tremolada, Fabrizio; Erba, Elisabetta; Bralower, Timothy J.
Author Affiliation(s): Primary:
RPS Group, RPS Energy, Wokingey, United Kingdom
Universita di Urbino Carlo Bo, Italy
New York University, United States
Universita di Milano, Italy
Pennsylvania State University, United States
Volume Title: Large ecosystem perturbations; causes and consequences
Volume Author(s): Monechi, Simonetta, editor; Coccioni, Rodolfo; Rampino, Michael R.
Source: Large ecosystem perturbations; causes and consequences, edited by Simonetta Monechi, Rodolfo Coccioni and Michael R. Rampino. Special Paper - Geological Society of America, Vol.424, p.87-96. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0072-1077. ISBN: 978-0-8137-2424-9 CODEN: GSAPAZ
Note: In English. NSF grants OCE-0084032, EAR-9814604 and EAR 0120727. 106 refs.; illus., incl. sketch maps
Summary: The comparison between calcareous nannofossils during the early Aptian Oceanic Anoxic Event 1a (OAE1a) and the Paleocene-Eocene Thermal Maximum (PETM) suggests different nannofloral reactions to extreme greenhouse conditions. Both events were likely characterized by major changes in nutrient concentrations, temperature, and pCO2 levels. OAE1a corresponds to an increase in opportunistic taxa associated with eutrophic surface-water conditions. Eutrophy also resulted in the demise of an oligotrophic group, the nannoconids. Nannofloral assemblages of the PETM interval suggest nutrient-depleted surface waters at open-ocean sites including those at high and low latitudes. However, the upper part of the PETM shows a return to mesotrophic conditions documented by the increase in abundance of mesotrophic taxa. PETM records from shelf sites are characterized by an increase in nannofossil taxa indicative of mesotrophic conditions, suggesting an increase in productivity. Fluctuations in primary productivity affected composition and abundance of calcareous nannofossil assemblages during both events. Whereas fertility increased in the global ocean during OAE1a, mesotrophic conditions mostly characterized proximal settings during the PETM. Nannofloral changes could have been partially triggered by the warming, but the influence of high pCO2 levels is not evident. Reductions in nannofossil calcification and paleofluxes are associated with the OAE1a, but the role of pCO2 variations in nannofloral calcification during the PETM is not obvious. In both events, variations in lysocline/CCD depth and enhanced dissolution and/or diagenesis strongly affected nannofossil assemblages in some locations, but the overall nannofloral changes reveal a primary paleoecological and paleoceanographic signal.
Year of Publication: 2007
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Algae; Aptian; Assemblages; Atlantic Ocean; C-13/C-12; Carbon; Carbon dioxide; Cenozoic; Cretaceous; DSDP Site 527; DSDP Site 534; Deep Sea Drilling Project; Eocene; IPOD; Isotope ratios; Isotopes; Leg 113; Leg 143; Leg 165; Leg 171B; Leg 198; Leg 199; Leg 207; Leg 208; Leg 74; Leg 76; Lower Cretaceous; Mediterranean region; Mesozoic; Microfossils; Nannofossils; ODP Site 1000; ODP Site 1001; ODP Site 1049; ODP Site 1051; ODP Site 1208; ODP Site 1209; ODP Site 1210; ODP Site 1211; ODP Site 1212; ODP Site 1215; ODP Site 1220; ODP Site 1221; ODP Site 1257; ODP Site 1258; ODP Site 1259; ODP Site 1260; ODP Site 1261; ODP Site 1262; ODP Site 1263; ODP Site 1265; ODP Site 1266; ODP Site 1267; ODP Site 690; ODP Site 865; ODP Site 999; Ocean Drilling Program; Pacific Ocean; Paleocene; Paleoclimatology; Paleoecology; Paleogene; Paleotemperature; Plantae; Productivity; Southern Ocean; Stable isotopes; Tertiary; Weddell Sea
Coordinates: N182624 N182626 W1793320 W1793321
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Record ID: 2007111303
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