HR: 1330h
AN: PP12A-0231    [PDF]
TI: ODP Hole 1000A, Northern Nicaragua Rise, Caribbean Sea: Further Evidence of Globally Synchronous Intervals of Carbonate Preservation and Dissolution During the Quaternary?
AU: * Shearer, M C
EM: mshearer@rice.edu
AF: Rice University, Department of Earth Science MS-126 P.O. Box 1892, Houston, TX 77251 United States
AU: Droxler, A W
EM: andre@rice.edu
AF: Rice University, Department of Earth Science MS-126 P.O. Box 1892, Houston, TX 77251 United States
AU: Ferraro, L
EM: ferraro@gms01.geomare.na.cnr.it
AF: Instituto per l"Ambiente Marino Costiero (CNR), Sezione Geomare Sud Porto di Napoli Calata Porta di Massa n.80, Napoli, 80133 Italy
AB: New Quaternary records of carbonate, aragonite, and high Mg-calcite content and pteropod abundance developed for ODP Hole 1000A (903 m WD, Pedro Channel, northern Nicaragua Rise, Caribbean Sea) show remarkable similarity to records from periplatform sites in the Bahamas and the Maldives, suggesting a possible global synchronicity in some intervals of carbonate preservation and dissolution. Comparison of these records shows 1) a distinct change in phase relationships and glacial/interglacial values at approximately 1.2 Ma and, 2) similar timing of strong carbonate dissolution at 0.3-0.5, 0.85-0.95, and 1.3-1.6 Ma. The Quaternary at ODP Hole 1000A corresponds to a 60 m-thick sequence of periplatform ooze characterized by an average sedimentation rate of 3.6 cm/ky. An excellent continuous high-resolution stratigraphy (10 cm sampling intervals correspond to 3 ky between consecutive samples) constructed from benthic stable isotope analysis of C. wuellerstorfi, nannofossil stratigraphy, and identification of the Bruhnes-Matuyama reversal provides the chronostratigraphic framework for the carbonate dissolution records at ODP Hole 1000A. Interglacial percent carbonate of the fine sediment fraction ($<$ 62 micron) is relatively stable during the Quaternary, ranging from 85-90%, while glacial values are more variable at 62-77%. Early Quaternary percent carbonate is somewhat out of phase with benthic oxygen isotopes from 2.0-1.2 Ma, when the two records shift to become consistently in phase during the late Quaternary. The aragonite component of the fine carbonate fraction shows a similar shift to become in phase with the benthic oxygen isotope record at 1.2 Ma, but is also accompanied by a distinct amplitude increase between glacial and interglacial values. High Mg-calcite is completely absent from 2.0-1.2 Ma, then gradually appears during the late Quaternary. Prior to 1.2 Ma, pteropods are poor to completely absent. Carbonate, aragonite, high Mg-calcite, and pteropod abundance all indicate strong dissolution at 0.3-0.5, 0.85-0.95, and 1.3-1.6 myr. Low values during the same intervals are seen in records of carbonate, aragonite, high Mg-calcite, and pteropod abundance from ODP Hole 633A in the Bahamas and ODP Hole 716B in the Maldives and have been interpreted as strong dissolution. Both sites also show remarkably similar late versus early Quaternary patterns. The timing of these dissolution intervals is surprisingly close to the timing of strong dissolution observed in the Indo-Pacific at abyssal depths, suggesting a possible global aspect to these dissolution events.
DE: 4267 Paleoceanography
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting