Hostname: page-component-78c5997874-m6dg7 Total loading time: 0 Render date: 2024-11-17T15:24:07.426Z Has data issue: false hasContentIssue false
  • English
  • Français

Mineralogy and geochemistry of Mesozoic black shales and interbedded carbonates, southeastern Sicily: evaluation of diagenetic processes

Published online by Cambridge University Press:  01 May 2009

E. Azzaro ,
A. Bellanca  and
R. Neri
E. Azzaro
Affiliation:
Istituto di Mineralogia, Petrografia e Geochimica, Università di Palermo, Via Archirafi 36, 90123-Palermo, Italy
A. Bellanca
Affiliation:
Istituto di Mineralogia, Petrografia e Geochimica, Università di Palermo, Via Archirafi 36, 90123-Palermo, Italy
R. Neri
Affiliation:
Istituto di Mineralogia, Petrografia e Geochimica, Università di Palermo, Via Archirafi 36, 90123-Palermo, Italy
Get access Rights & Permissions [Opens in a new window]

Abstract

Upper Triassic/Lower Jurassic organic-rich shales and interbedded carbonates (Rhaetian → Sinemurian) are widespread in the subsurface of southeastern Sicily where important oil fields have been found hosted in Triassic reservoirs. Core samples from wells drilled offshore and onshore were studied from petrographie and geochemical viewpoints.

In the Hettangian/Sinemurian shale-carbonate sequences, which accumulated in a rapidly subsiding basin, the micritic aragonitic mud is still largely preserved. Mixed-layer I/S has remained randomly interstratified to a depth > 4000 m. Diagenetic carbonates are non-stoichiometric finely crystalline, pore-filling dolomite and/or calcite. The carbonate component exhibits a high Sr content and fair amounts of Fe and Mn. Carbon and oxygen isotopic values suggest a subsurface interstitial formation for the digenetic carbonates in an essentially closed system. Based on all accumulated data it is suggested that anoxic marine waters were retained in the sediment pores for a long time after deposition, thus enhancing the preservation of significant amounts of the original organic matter.

In contrast, Rhaetian tidal-flat deposits hosting black shales display a clay component characterized by ordered illite-rich I/S and a carbonate mineralogy dominated by low-Mg calcite in the uppermost beds and by near-stoichiometric dolomite in the lowermost ones. Petrographie, chemical and isotopic data indicate early cementation in an oxidizing phreatic environment and lower down in the sequence pervasive dolomitization in a sabkha-type environment.

Type
Articles
Information
Geological Magazine , Volume 130 , Issue 2 , March 1993 , pp. 191 - 202
Copyright
Copyright © Cambridge University Press 1993

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Agip. 1977. Temperature Sotterranee. Inventario dei Dati Raccolti dall' Agip durante la Ricerca e la Produzione di Idrocarburi in Italia. San Donato Milanese: Agip Mineraria.Google Scholar
Anonymous. 1968. Analytical Methods for Atomic Absorption Spectrophotometry. Norwalk: Perkin Elmer Corporation.Google Scholar
Baker, P. A., Gieskes, J. M. & Elderfield, H. 1982. Diagenesis of carbonates in deep-sea sediments - evidence from Sr/Ca ratios and interstitial dissolved Sr2+ data. Journal of Sedimentary Petrology 52, 71–82.Google Scholar
Barahona, E., Huertas, F., Pozzuoli, A. & Linares, J. 1982. Mineralogia e genesi dei sedimenti della provincia di Granada (Spagna). Mineralogica et Petrographica Acta 26, 61–90.Google Scholar
Becker, R. H. & Clayton, R. N. 1972. Carbon isotope evidence for the origin of a banded iron-formation in Western Australia. Geochimica et Cosmochimica Acta 36, 577–96.CrossRefGoogle Scholar
Bellanca, A., Fustaino, G. & Neri, R. 1990. Petrografia e geochimica isotopica di reservoir carbonatici del Trias, Sicilia sud-orientale. Mineralogica et Petrographica Acta 33, 305–18.Google Scholar
Biscaye, P. E. 1965. Mineralogy and sedimentation of recent deep sea clays in the Atlantic Ocean and adjacent seas and oceans. Geological Society of America Bulletin 76, 803–32.CrossRefGoogle Scholar
Chafetz, H. S., McIntosh, A. G. & Rush, P. F. 1988. Freshwater diagenesis in the marine realm of Recent Arabian Gulf carbonates. Journal of Sedimentary Petrology 58, 433–40.Google Scholar
Claypool, G. E. & Kaplan, I. R. 1974. The origin and distribution of methane in marine sediments. In Natural Gases in Marine Sediments (ed. Kaplan, I. R.), pp. 99–139. New York: Plenum.CrossRefGoogle Scholar
Craig, H. 1965. The measurement of oxygen isotope paleotemperatures. In Stable Isotopes in Oceanographie Studies and Paleotemperatures (ed. Tongiorgi, E.), pp. 1–24. Proc. Spoleto Conf. Roma: Consiglio Nazionale delle Ricerche.Google Scholar
Epstein, S., Buchsbaum, R., Lowenstan, H. & Urey, H. C. 1953. Revised carbonate-water isotopic temperature scale. Geological Society of America Bulletin 64, 1315–26.CrossRefGoogle Scholar
Epstein, S., Graf, D. L. & Degens, E. T. 1964. Oxygen isotope studies on the origin of dolomites. In Isotopic and Cosmic Chemistry (eds Craig, H., Miller, S. L. and Wassenburg, G. T.), pp. 169–80. Amsterdam: North Holland.Google Scholar
Franzini, M., Leoni, L. & Saitta, M. 1975. Revisione di una metodologia analitica per fluorescenza X basata sulla correzione completa degli effetti di matrice. Rendiconti della Società Italiana di Mineralogia e Petrologia 21, 99–108.Google Scholar
Freed, R. L. & Peacor, D. R. 1989. Variability in temperature of the smectite/illite reaction in Gulf Coast sediments. Clay Minerals 24, 171–80.CrossRefGoogle Scholar
Freeman-Lynde, R. P., Fulker Whitley, K. & Lohmann, K. C. 1986. Deep-marine origin of equant spar cements in Bahama escarpment limestones. Journal of Sedimentary Petrology 56, 799–811.Google Scholar
Friedman, G. M. 1959. Identification of carbonate minerals by staining methods. Journal of Sedimentary Petrology 29, 87–97.Google Scholar
Fritz, P. & Smith, D. G. W. 1970. The isotopic composition of secondary dolomites. Geochimica et Cosmochimica Acta 34, 1161–73.CrossRefGoogle Scholar
Griffin, G. M. 1971. Interpretation of X-ray diffraction data. In Procedures in Sedimentary Petrology (ed. Carver, R. E.), pp. 541–70. New York: Wiley-Interscience.Google Scholar
Grossman, E. L. & Ku, T. L. 1986. Oxygen and carbon isotope fractionation in biogenic aragonite: temperature effects. Chemical Geology (Isotopic Geoscience Section) 59, 59–74.CrossRefGoogle Scholar
Jenkyns, H. C. & Clayton, C.J. 1986. Black shales and carbon isotopes in pelagic sediments from the Tethyan Lower Jurassic. Sedimentology 33, 87–106.CrossRefGoogle Scholar
Kelts, K. & McKenzie, J. A. 1982. Diagenetic dolomite formation in Quaternary anoxic diatomaceous muds of Deep Sea Drilling Project Leg 64, Gulf of California. Deep Sea Drilling Project Initial Reports 64, 553–69.Google Scholar
Land, L. S. 1980. The isotopic and trace element geochemistry of dolomite: the state of the art. In Concepts and Models of Dolomitization (eds Zenger, D. H., Dunham, J. B. and Ethington, R. L.), pp. 87–110. Tulsa: Society of Economic Paleontologists and Mineralogists, Special Publication no. 28.CrossRefGoogle Scholar
Longman, M. W. 1980. Carbonate diagenetic textures from nearsurface diagenetic environments. American Association of Petroleum Geologists Bulletin 64, 461–87.Google Scholar
Lorens, R. B. 1981. Sr, Cd, Mn and Co distribution coefficients in calcite as a function of calcite precipitation rate. Geochimica et Cosmochimica Acta 45, 553–62.CrossRefGoogle Scholar
Lumsden, D. N. 1988. Characteristics of deep-marine dolomite. Journal of Sedimentary Petrology 41, 1045–58.Google Scholar
MacEwan, D. M. C. & Wilson, M. J. 1980. Interlayer and intercalation complexes of clay minerals. In Crystal Structures of Clay Minerals and their X-ray Identification (eds Brindley, G. V. and Brown, G.), pp. 197–248. London: Mineralogical Society.CrossRefGoogle Scholar
McHargue, T. R. & Price, R. 1982. Dolomite from clay in argillaceous or shale-associated marine carbonates. Journal of Sedimentary Petrology 52, 873–86.Google Scholar
Machel, H. G. & Anderson, J. H. 1989. Pervasive subsurface dolomitization of the Nisku Formation in Central Alberta. Journal of Sedimentary Petrology 59, 891–911.Google Scholar
McKenzie, J. A. 1981. Holocene dolomitization of calcium carbonate sediments from the coastal sabkhas of Abu, Dhabi U.A.E.: a stable isotope study. Journal of Geology 89, 185–98.CrossRefGoogle Scholar
Mattavelli, L. & Novelli, L. 1990. Geochemistry and habitat of the oils in Italy. American Association of Petroleum Geologists Bulletin 74, 1623–39.Google Scholar
Neri Bellanca, A., Neri, R. & Schifano, G. 1975. La determinazione diffrattometrica della frazione carbonatica delle rocce calcaree. Periodico di Mineralogia 44, 41–53.Google Scholar
Northrop, D. A. & Clayton, R. N. 1966. Oxygen isotope fractionation in systems containing dolomite. Journal of Geology 74, 174–96.CrossRefGoogle Scholar
Novelli, L., Welte, D. H., Mattavelli, L., Yalcin, M. N., Cinelli, D. & Schmitt, K. J. 1988. Hydrocarbon generation in southern Sicily: a three-dimensional computer-aided basin modeling study. In Advances in Organic Geochemistry (eds Mattavelli, L. and Novelli, L.), pp. 153–64. Oxford: Pergamon Press.Google Scholar
O'Brien, N. R. & Slatt, R. M. 1990. Argillaceous Rock Atlas. New York: Springer-Verlag. 141 pp.CrossRefGoogle Scholar
Patacca, E., Scandone, P., Giunta, G. & Liguori, V. 1979. Mesozoic paleotectonic evolution of the Ragusa zone (southeastern Sicily). Geologica Romana 18, 331–69.Google Scholar
Pearson, M. J. & Small, J. S. 1988. Illite-smectite diagenesis and palaeotemperatures in northern North Sea Quaternary to Mesozoic shale sequences. Clay Minerals 23, 109–32.CrossRefGoogle Scholar
Pisciotto, K. A. 1981. Review of secondary carbonates in the Monterey Formation, California. In The Monterey Formation and Related Siliceous Rocks of California (eds Garrison, R. E., Douglas, R. G. and Pisciotto, K. E.), pp. 273–83. Tulsa: Society of Economic Paleotologists and Mineralogists, Special Publication.Google Scholar
Reynolds, R. C. 1980. Interstratified clay minerals. In Crystal Structures of Clay Minerals and their X-ray Identification (eds Brindley, G. W. and Brown, G.), pp. 249–303. London: Mineralogical Society.CrossRefGoogle Scholar
Royse, C. F., Wadell, J. S. & Petersen, L. E. 1971. X-ray determination of calcite-dolomite: an evaluation. Journal of Sedimentary Petrology 41, 483–8.Google Scholar
Schultz, L. G. 1964. Quantitative interpretations of mineralogical composition from X-ray and chemical data for the Pierre Shale. U.S. Geological Survey Professional Paper 391–C.CrossRefGoogle Scholar
Sheppard, S. M. F. & Schwarcz, H. P. 1970. Fractionation of carbon and oxygen isotopes and magnesium between coexisting metamorphic calcite and dolomite. Contributions to Mineralogy and Petrology 26, 161–98.CrossRefGoogle Scholar
Srodon, J. 1981. X-ray identification of randomly interstratified illite-smectite in mixtures with discrete illite. Clay Minerals 16, 297–304.CrossRefGoogle Scholar
Stein, R., Rullkötter, J. & Welte, D. H. 1986. Accumulation of organic-carbon-rich sediments in the late Jurassic and Cretaceous Atlantic Ocean - a synthesis. Chemical Geology 56, 1–32.CrossRefGoogle Scholar
Tarutani, T., Clayton, R. N. & Mayeda, T. K. 1969. The effect of polymorphism and magnesium substitution on oxygen isotope fractionation between calcium carbonate and water. Geochimica et Cosmochimica Acta 33, 987–96.CrossRefGoogle Scholar
Tucker, M. E. 1986. Formerly aragonitic limestones associated with tillites in the late Proterozoic of Death Valley, California. Journal of Sedimentary Petrology 56, 818–30.Google Scholar
Turekian, K. K. & Armstrong, R. L. 1960. Magnesium, strontium and barium concentrations and calcite-aragonite ratios of some recent molluscan shells. Journal of Marine Research 18, 133–51.Google Scholar
Warren, J. K. 1986. Perspectives: shallow-water evaporitic environments and their source rock potential. Journal of Sedimentary Petrology 56, 442–54.CrossRefGoogle Scholar
Whitney, G. 1990. Role of water in the smectite-to-illite reaction. Clays and Clay Minerals 38, 343–50.CrossRefGoogle Scholar
Wilson, M. J. 1987. X-ray powder diffraction methods. In A Handbook of Determinative Methods in Clay Mineralogy (ed. Wilson, M. J.), pp. 26–97. Glasgow and London: Blackie.Google Scholar