Oxygen isotopes

CARBON AND OXYGEN STABLE ISOTOPES IN THE TOA BAJA WELL, PUERTO RICO: IMPLICATIONS FOR BURIAL DIAGENESIS AND HYDROCARBON GENERATION

GONZALEZ, LA. 1991. Carbon and oxygen stable isotopes in the toa-baja well, puerto-rico - implications for burial diagenesis and hydrocarbon generation rid D-5476-2011. Geophysical Research Letters 18 (3) (MAR): 533-6.

Abstract: 
The Toa Baja Well was drilled on the coastal plains of northern Puerto Rico with a total depth of 2705m [Larue, 1990]. Interstratified limestone, quartz-bearing calcareous sandstones, and shales dominate the uppermost 580 m and are separated from underlying rocks by an unconformity. Below this unconformity continuing tototal depth, lithologies encountered consist of volcaniclastic sandstones/siltstones, pelagic carbonates, volcanic flows and either plutonic rocks or coarse-grained immature sandstones derived from plutonic bodies....

Testing coral-based tropical cyclone reconstructions: An example from puerto rico

Kilbourne, K. Halimeda, Ryan P. Moyer, Terrence M. Quinn, and Andrea G. Grottoli. 2011. Testing coral-based tropical cyclone reconstructions: An example from puerto rico. Palaeogeography Palaeoclimatology Palaeoecology 307 (1-4) (JUL 1): 90-7.

Abstract: 
Complimenting modern records of tropical cyclone activity with longer historical and paleoclimatological records would increase our understanding of natural tropical cyclone variability on decadal to centennial time scales. Tropical cyclones produce large amounts of precipitation with significantly lower δ18O values than normal precipitation, and hence may be geochemically identifiable as negative δ18O anomalies in marine carbonate δ18O records. This study investigates the usefulness of coral skeletal δ18O as a means of reconstructing past tropical cyclone events. Isotopic modeling of rainfall mixing with seawater shows that detecting an isotopic signal from a tropical cyclone in a coral requires a salinity of ~33 psu at the time of coral growth, but this threshold is dependent on the isotopic composition of both fresh and saline end-members. A comparison between coral δ18O and historical records of tropical cyclone activity, river discharge, and precipitation from multiple sites in Puerto Rico shows that tropical cyclones are not distinguishable in the coral record from normal rainfall using this approach at these sites.

Seasonal changes in sea surface temperature and salinity during the little ice age in the caribbean sea deduced from Mg/Ca and O-18/O-16 ratios in corals

Watanabe, T., A. Winter, and T. Oba. 2001. Seasonal changes in sea surface temperature and salinity during the little ice age in the caribbean sea deduced from Mg/Ca and O-18/O-16 ratios in corals. Marine Geology 173 (1-4) (MAR 15): 21-35.

Abstract: 
The oxygen isotropic composition (delta 18O) of coral skeletons reflects a combination of sea surface temperature (SST) and the delta 18O of seawater, which is related to sea surface salinity (SSS). In contrast, the magnesium/Calcium (Mg/Ca) ratio of a coral skeleton reflects SST independent of Salinity. by using the relationships among coral Mg/Ca ratios, coral delta 18), seawater delta 18O and SST, it is possible to determine past SST and SS uniquely. Such determinations were made and calibrated using the Mg/Ca ratio and the delta 18O of the modern part of a 3 m long coral core (Monastrea faveolata) collected from the southwest coast of Puerto Rico in the Caribbean Sea where both SST and SSS changes seasonally and the seawater delta 18O measured at the coral site....

Evaluation of the fidelity of isotope records as an environmental proxy in the coral Montastraea

Watanabe, T., A. Winter, T. Oba, R. Anzai, and H. Ishioroshi. 2002. Evaluation of the fidelity of isotope records as an environmental proxy in the coral montastraea. Coral Reefs 21 (2) (JUL): 169-78.

Abstract: 
Many studies of climate variability in the Tropical Ocean have used high-resolution chemical tracer records contained in coral skeletons. The complex architecture of coral skeletons may lead to the possibility of biases in coral records and it is therefore important to access the fidelity of coral geochemical records as environmental proxies. Coral skeletal records from the same coral colony, and even the same corallite, may show large variation due to differing extension rates, formational timing of the skeletal elements, colony topography, and sampling resolution. To assess the robustness of the skeletal record, we present d13C and d18O data based on different sampling resolutions, skeletal elements, and coral colonies of Montastraea faveolata species complex, the primary coral used for climate reconstruction in the Atlantic. We show that various skeletal elements produce different isotopic records. The best sampling rate to resolve the full annual range of sea surface temperature (SST) is 40 samples per year. This sampling frequency also consistently recovered SST variability measured at weekly intervals. A sampling rate of 12 times per year recovered 84% of the annual range recording average monthly SST changes through the year. Six samples per year significantly decreased the ability to resolve the annual SST range. The d18O recorded from two adjacent colonies were very similar, suggesting that this isotope can be trusted to record environmental changes. The d13C, on the other hand, remained highly variable, perhaps as a result of the activity of symbiotic algae (zooxanthellae).
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