Diagenesis and Geochemistry of Upper Muschelkalk (Triassic) buildups and associated facies in Catalonia (NE Spain) : a paper dedicated to Francesc Calvet
DOI:
https://doi.org/10.1344/105.000001418Keywords:
Muschelkalk, Triassic reefs, C and O isotopes, Trace element geochemistry, CataloniaAbstract
Carbonate buildups are well developed in the Triassic Upper Muschelkalk of eastern Spain in the La Riba Unit, but they are completely dolomitised. These mud-mounds with reefal caps have well-developed fibrous and botryoidal marine cements which were probably high-Mg calcite and aragonite originally. The dolomite is fabric retentive indicating an early origin, but the d18O values are quite negative (average -3.‰), interpreted as indicating recrystallisation during shallow burial, but without fabric destruction. Low Sr and Na contents support this. The d13C signature is quite uniform (~ +1‰) and this is probably the inherited, original marine CaCO3 value. The Alcover Unit, deposited between and above the La Riba buildups after a sea-level fall terminated mound growth, is an organic-rich laminated dolomicrite with exquisitely-preserved fossils. The d18O signature (average –3.4‰) is similar to the La Riba dolomites, also interpreted as suggesting recrystallisation. The d13C values, however, show a stratigraphic trend of increasingly negative (to –5.5‰) and then more positive to marine values (~0‰), over a thickness of 10 metres. This is interpreted as a reflection of increasing stratification and developing anoxia, which would have led to the preservation of the special fossils, and then a return to conditions of more open-marine circulation. The dolomicrites of the Alcover unit may well have been formed on or close to the sea-floor. Recrystallisation of the dolomites took place during shallow to moderate burial, with the resetting of the d18O signatures and loss of Sr. The dolomitisation of the La Riba Unit is attributed to circulating seawater, probably driven by sea-level change, during deposition of the Alcover Unit or shortly thereafter.
References
Burns, S.J., McKenzie, J.A., Vasconcelos, C., 2000. Dolomite formation and biogeochemical cycles in the Phanerozoic. Sedimentology, 47, Sp. 1, 49-61
Calvet, F., Tucker, M.E., 1988. Outer ramp cycles in the Upper Muschelkalk of the Catalan Basin, northern Spain. Sedimentary Geology, 57, 185-198.
Calvet, F., Tucker, M.E., 1995. Mud-mounds with reefal caps in the Upper Muschelkalk (Triassic), eastern Spain. In: Monty,
C.L.V., Bosence, D.B., Bridges, P., Pratt, B. (eds.). Mud Mounds: Origin and Evolution. Oxford. Blackwell Scientific Publications. International Association of Sedimentologists, Special Publication, 23, 311-333.
Calvet, F., Tucker, M.E., Henton, J.M., l990. Middle Triassic carbonate ramp systems in the Catalan Basin, northeast Spain: facies, systems tracts, sequences and controls. In: Tucker, M.E. (ed.). Carbonate Platforms. Oxford. Blackwell Scientific Publications. International Association of Sedimentologists, Special Publication, 9, 79-108.
Calvet, F., Tucker, M.E., Hunt, D., 1993. Sequence stratigraphy of carbonate ramps: systems tracts, models and application
to the Muschelkalk carbonate platforms of eastern Spain. In: Posamentier, H.W., Summerhayes, C.P., Haq, B.U., Allen, G.P. (eds.). Sequence Stratigraphy and Facies Associations. Oxford, Blackwell Scientific Publications. International Association of Sedimentologists, Special Publication, 18, 397-415.
Cartaña, J., 1994. Noves aportacions paleontologiques al Muschelkalk superior de les Muntanyes de Prades el cas del Pinetell. Quaderns de Vilaniu, 25, 67-93.
Frisia-Brune, S., Jadoul, F., Weissert, H., 1989. Evinosponges in the Triassic Esino Limestone (Southern Alps): documentation of early lithification and late diagenetic overprint. Sedimentology, 36, 685-699.
James, N.P., Choquette, P.W., 1983. Diagenesis 6. Limestones - the sea-floor diagenetic environment. Geoscience Canada,
, 162-179.
Keim, L., Schlager, W., 2001. Quantitative compositional analysis of a Triassic carbonate platform (Southern Alps, Italy). Sedimentary Geology, 139, 261-283.
Kelts, K., McKenzie, J.A., 1982. Diagenetic dolomite formation in Quaternary anoxic diatomaceous muds of DSDP Leg 64,
Gulf of California. In: Curray, J.R., Moore, D.G. et al. (eds.). Initial Reports of the Deep Sea Drilling Project. Washington, D.C. US Government Printing Office, 64, 553-569.
Marzo, M., Calvet, F., 1985. Guia de la excursion al Triasico de los Catalanides. La Seu d’Urgell, Spain, II Coloquio de Estratigrafia y Paleogeograpfia de Permico y Triasico de España, 175 pp.
Martínez-Delclòs, X. (ed.), 1995. Montsec & Montral-Alcover. II International Symposium on Lithographic Limestones. Field Trip Guide. Institut d’estudis Ilerdencs, 97 pp.
Reitner, J., Neuweiler, F., 1995. Mud mounds: a polygenetic spectrum of fine-grained carbonate buildups. Facies, 32, 1-69.
Scherer, M., 1977. Preservation, alteration, and multiple cementation of aragonite skeletons from the Cassian Beds (Southern Alps), petrographical and geochemical evidence. Neues Jahrbuch Geologisch Paläontologisch Abhandlung, 154, 213-262.
Török, A., 2000. Formation of dolomite mottling in Middle Triassic ramp carbonates (Southern Hungary). Sedimentary Geology, 131, 131-145. Tucker, M.E., Wright, V.P., 1990. Carbonate Sedimentology. Oxford, Blackwell Scientific Publications, 482 pp.
Veizer, J. et al., 1999. 87Sr/86Sr, 13C and 18O evolution of Phanerozoic seawater. Chemical Geology, 161, 59-88.
Virgili, C., 1958. El Triasico de los Catalanides. Boletín del Instituto de Geología y Mineralogía de España, 69, 1-856.
Wolf, K.H., 1965. Gradational sedimentary products of calcareous algae. Sedimentology, 5, 1-37.
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