Chemostratigraphic and Paleoenvironmental Analysis of Rudist Facies in Cretaceous Strata

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1 Chemostratigraphic and Paleoenvironmental Analysis of Rudist Facies in Cretaceous Strata Luis González, Hernan Santos (UPRM), Robert H. Goldstein, Alvin Bonilla STATUS: Long-term project near completion TIMING: In review and in press publications available to membership FUNDING: KICC-partial Purpose This study improves our understanding the conditions that led to the dominance of rudists over corals as the major reef builder in the tropics. The Aptian-Albian and Santonian are particular targets as it has been suggested that warming on the Caribbean Tethys (Super Tethys) (Figure 1) displaced corals to higher latitudes allowing for dominance by rudists. The late Early and Late Cretaceous are of great interest as numerous northern South American source rocks and reservoirs probably owe their high OMC to the prevailing oceanographic and paleoclimatic conditions. In addition this study improves the chronostratigraphic framework for the mid- Cretaceous of the northeastern Caribbean Project Description The Cretaceous was characterized by CO 2 concentration believed in excess of 1000 ppm, (Skelton, 2003). Geologic evidence from the Cretaceous greenhouse world suggests that ocean circulation, a major temperature buffer in today s tropical oceans, failed during the Cretaceous. Overheating in the tropics led to decimation of reef-building corals and the evolution and dominance of rudist bivalve as reef builders. Modern reef building corals can tolerate temperatures C and salinities that range from ppt. The environmental limits for corals has led to the suggestion that variations in Caribbean reef builders during the Cretaceous were controlled by the episodic development overheated and hypersaline oceanic zones in the eustatically elevated Cretaceous ocean in the central paleotropics (i.e., Supertethys) (Kauffman and Johnson, 1996). Johnson et al. (1996) explored the heat export hypotheses against latitudinal fluctuations of Cretaceous tropical reef boundaries in the Caribbean region. Their results consistently show a dynamic history of episodic contractions and expansions of reef boundary lines. In this scheme, the paleotropical environments were highly dynamics in shallow marine ecosystems (Kauffman and Johnson, 1988). Johnson et al. (1996), reconstructed two major geographic expansions of Caribbean rudist reefs that were associated with the development of the Supertethyan midtropical zone. The first expansion occurred in the Albian and the second occurred in the Santonian, and major rudist diversity peaks followed these expansions. Global Circulation Models (GCM) support the idea that these expansions occurred in overheated and hypersaline oceanic conditions. Our studies provide support for the Johnson et al. (1996) model. Our isotope mass balance modeling of Aptian-Albian paleoprecipitation, require that Tehthyan surface sea water be evaporatively enriched by as much of as 2, and would result in increase salinities (Suarez et al. 2011). Furthermore, preliminary 18 O derived Santonian marine temperatures and fluid inclusion salinities indicate ~32 C and ~40 ppt) dissolved salt, respectively. Kansas Interdisciplinary Carbonates Consortium Proposal June

2 This study uses 13 C chemostratigraphy and 86 Sr/ 86 Sr to constrain and correlate the carbonate depositional periods in the Greater Antilles Early Cretaceous strata. Rudist 18 O schlerochronology is used to constrain ocean paleotemperatures and fluid inclusion analysis of early marine cements is used to constrain salinities. Early meteoric diagenetic calcite is used to constrain paleoprecipitation. The resulting chronostratigraphic framework coupled with the schlerochronology and fluid inclusion analysis is used to improve paleogeographic, paleoceanographic and paleoclimatic reconstructions of the Cretaceous in the Caribbean region. Current results from chemostratigraphic analyisis (Figure 2) suggest a change in circulation within the Caribbean occurred during the latest Early Albian to early Midle Albian (Figure 3). Deliverables Model of paleoceanographic conditions (sea surface temperature, oceanic circulation, paleosalinities) for the Aptian-Albian and Santonian of the Caribbean. An improved high-resolution chemostratigraphic framework for the late Early and Late Cretaceous. TOC analysis of northern Caribbean Cretaceous strata. These strata are time equivalent with northern South American oil bearing strata such as la Luna (Venezuela) and Caballos (Colombia) formations. References BRALOWER, T.J., COBABE, E., CLEMENT, B., SLITER, W.V., OSBURN, C.L., LONGORIA, J., 1999, The record of global change in Mid-Cretaceous (Barremian-Albian) sections from the Sierra Madre, northeastern Mexico: Journal of Foraminiferal Research, v. 29, p GALE, A. S., BOWN, P., CARON, M., CRAMPTON, J., CROWHURST, S. J., KENNEDY, W. J., PETRIZZO, M. R., AND WRAY, D. S., 2011, The uppermost Middle and Upper Albian succession at the Col de Palluel, Hautes-Alpes, France: An integrated study (ammonites, inoceramid bivalves, planktonic foraminifera, nannofossils, geochemistry, stable oxygen and carbon isotopes, cyclostratigraphy): Cretaceous Research, v. 32, p HERRLE, J.O., KÖßLER, P., FRIEDRICH, O., ERLENKEUSER, H., HEMLEBEN, C., 2004, High-resolution carbon isotope records of the Aptian to Lower Albian from SE France and the Mazagan Plateau (DSDP Site 545): A stratigraphic tool for paleoceanographic and paleobiologic reconstruction: Earth and Planetary Science Letters, v. 218, p JOHNSON, C. C., 1999, Evolution of Cretaceous surface current circulation patterns, Caribbean and Gulf of Mexico, in Barrera, E., and Johnson, C. C., ed., Evolution of the Cretaceous ocean-climate systems: Geological Society of America, Special Paper 332, p JOHNSON, C.C, BARRON, E.J., KAUFFMANN, E.G., ARTHUR, M.A., FAWCETT, P.J., YASUDA, M.K., 1996, Middle Cretaceous reef collapse linked to ocean heat transport: Geology, v. 24, p KAUFFMAN E.G., AND JOHNSON C.C., 1996, The morphological and ecological evolution of middle and Upper Cretaceous reef building rudistids: Theme Issue: Ancient reef ecosystems, PALAIOS, v. 3, p PHELPS, R.M., 2011, Middle-Hauterivian to Lower-Campanian sequence stratigraphy and stable isotope geochemistry of the Comanche platform, south Texas: Ph.D, University of Texas at Austin, Austin, Texas, 227 p. SKELTON, P.W., ed., 2003, The Cretaceous World: Cambridge University Press, New York, 360 p. SUAREZ, M. B., GONZALEZ, L.A., AND LUDVIGSON G.A., 2011, Quantification of a greenhouse hydrologic cycle from equatorial to polar latitudes: the mid-cretaceous water bearer revisited: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 307, p Kansas Interdisciplinary Carbonates Consortium Proposal June 2013

3 Figure 1. A) Paleographic reconstruction of the Tethys Ocean during the mid-cretaceous. B) Thethyan climatic zones. Orange area represents the possible distribution of the warmer and hypersaline marine climatic zone, Supertethys (ST); the greem area represents the normal distribution of the Tropical Tethyan climatic zone (after Kauffman and Johnson, 1996). Kansas Interdisciplinary Carbonates Consortium Proposal June

4 Figure 2. (A) Correlation of the Hatillo Limestone chemostratigraphy with the 13 C record from the Gulf of Mexico (Bralower et al., 1999; Phelps, 2011). (B) Correlation of the Hatillo Limestone chemostratigraphy with the 13 C record from the Mediterranean Tethys (Herrle et al., 2004; Gale et al., 2011). During the Late Aptian to Early 44 Kansas Interdisciplinary Carbonates Consortium Proposal June 2013

5 Figure 3. (A) Aptian and (B) Albian plate-tectonic and paleogeographic reconstructions (after: Pindell and Kennan, 2009) and surface oceanic currents flows (yellow arrows) within the Caribbean and Gulf of Mexico areas (after: Johnson, 1999). These figures illustrate the proposed changes in oceanic current and a better connection between the Caribbean and Gulf of Mexico during the Albian. DR Dominican Republic (this study); SM Sierra Madre in Mexico (Bralower et al., 1999); CS Comanche Shelf in Texas (Phelps, 2011). Kansas Interdisciplinary Carbonates Consortium Proposal June