Abstract
The Las Aguaditas Formation in the Argentine Precordillera of San Juan is the only Ordovician carbonate sequence deposited on a slope. Spiculites, mudstones and calcisiltites represent the autochthonous sediments, characterized by a fine lamination, rare fossils and their dark colour. The pelagic fauna consists of rare radiolarians/calcispheres, trinucleid trilobites, graptolites and conodonts. The latter are typical of an open marine environment and proved a Llanvirn—Llandeilo age for the Las Aguaditas Formation.
In the upper part of the succession there are several intercalations of megabreccias. Their thickness decreases from about 20 to 4 m towards the top of the formation, accompanied by an increasing amount of carbonate turbidites. The clasts of the breccias are derived from the slope as well as the platform. Each of the megabreccia horizons represents a system of channels, lobes and interchannel deposits, which together form a slope apron. On top of the lower breccia a small biostrome developed, where bryozoans and crinoids are preserved in an autochthonous position.
Sedimentation of the Las Aguaditas Formation started with the drowning of the underlying carbonate platform (San Juan limestones). Near the Arenig-Llanvirn boundary, a rapid ecstatic sea-level rise led to the deposition of graptolitic black shales and mudstones. Upwards, allochthonous carbonates become increasingly abundant. The onset of megabreccia deposition coincides with a major relative sea-level fall, caused by block movements in connection with rifting. The subsequent transition from breccia formation towards turbiditic sedimentation corresponds to an environmental shift from the slope towards the toe of slope and basin and marks a renewed moderate sea-level rise.
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References
Aigner T (1982) Calcareous Tempestites: Storm-dominated Stratification in Upper Muschelkalk Limestones (Middle Trias, SW-Germany). — In: Einsele G, Seilacher A (eds) Cyclic and Event Stratification, 180–198, Springer, Berlin Heidelberg New York
Astini RA (1988) Paleoambientes sedimentarios y secuencias depositacionales del Ordoviciao clástico de la Precordillera Argentina. PhD thesis (unpubl.) Univ Nac Córdoba (Argentina), 847 pp
Arthur MA, Schlanger SO (1979) Cretaceous “oceanic anoxic events” as causal factors in development of reef-reservoired oil fields. —Am Ass Petrol Geol Bull 63 870–885, Denver, Colorado
Baldis BA, Beresi MS (1981) Biofacies de culminación del ciclo deposicional calcáreo del Arenigiano en el Oeste de Argentina. II. Congr Lat-Am Paleontol Anais, 1: 11–17
Baldis BA, Beresi MS, Bordonaro O, Vaca A (1982) Sintesis evolutiva de la Precordillera Argentina. V. Congr Lat-Am Geol Acta 4: 399–445
Baldis BA, Gonzalez SB (1986) Australoharpes precordilleranus nov.sp. (Trilobita, Ptychopariida, Harpidae) del Ordoviciao Inferior de la Sierra de Villicum (Provincia de San Juan, Argentina). IV. Congr Arg de Paleontol y Bioestratigr Acta I: 73–79
Baldis BA, Gonzalez SB, Pires de Cavalho MG (1984) Una fauna arenigiana en la Sierra de Villicum (San Juan, Argentina) ubicada en las transfacies calcáreo-peliticas. 3. Congr Lat-Am Paleontol Acta : 68–72
Banchig AL, Bordonaro O (1990) Nuevos afloramientos del talud continental Cámbrico en la Sierra del Tontal, San Juan, Argentina. XI. Congr Geol Arg Acta 2: 49–52
Banchig AL, Keller M, Milana JP (1990a) Brechas calcáreas de la Formación Los Sombreros, Quebrada Ojos de Agua, Sierra del Tontal, San Juan. XI. Congr Geol Arg Acta 2: 149–152
Banchig AL, Milana JP, Bordonaro, O (1990b) Litofacies clásticas de la Formación Los Sombreros (Cámbrico Medic) en la Quebrada Ojos de Auga, Sierra del Tontal, San Juan. 3. Reunión Sed Arg: 25–30
Barnes CR, Williams SH (1991) Advances in Ordovician Geology Geol Surv Can Pap No 90-9
Benedetto JL, Vaccari NE Significado estratigráfico y tectónico de los complejos de bloques resedimentados Cambro-Ordovícicos de la Precordillera Occidental, Argentina. Estud Geol Madrid, in press
Benedetto JL, Cañas F, Astini R (1986) Braquiópodos y trilobites de la zona de transición entre las formaciones San Juan y Gualcamayo en el área de Guandacol (La Rioja, Argentina). IV. Congr Arg de Paleontol y Bioestratigr Acta I: 103–114
Bercowski F, Keller M, Bordonaro O (1990) Litofacies de la Formatión La Laja (Cámbrico) en la Sierra Chica de Zonda, Precordillera Sanjuanina, Argentina. 3. Reunion Sed Arg Acta: 31–36
Beresi MS (1986) Paleoecologia y Biofacies de la Formation San Juan al sur del paralelo 30° sur, Precordillera de San Juan. Unpubl PhD Thesis, Univ Nac San Juan, Argentina: 400 pp
Bergström SM (1971) Conodont Biostratigraphy of the Middle and Upper Ordovician of Europe and eastern North America. Geol Soc Am Mem 27: 83–162
Bergström SM (1983) Biogeography, evolutionary relationships and biostratigraphic significance of Ordovician platform conodonts. Fossils Strata 15: 35–58
Bordonaro O, Banchig AL (1990) Nuevos trilobites del Cámbrico Medio en la Quebrada Ojos de Agua, Sierra del Tontal, San Juan, Argentina. V. Congr Arg Paleontol y Bioestratigr Acta: 31–37
Cabaleri NG (1986) La transición entre las formaciones San Juan y Las Aguaditas al Sud-Sudoeste de Jáchal. I. J Geol Precordillera Acta: 42–45
Cabaleri NG (1987) Distribución de los efectos de la fase Guandacol en la Precordillera de San Juan — La Rioja (Argentina) basada en elementos tectosedimentarios. X. Congr Geol Arg Acta 3: 189–192
Cabaleri NG (1990) Arrecifes fangosos Ordovicicos (Llandeiliano) en la Formación Las Aguaditas, Jáchal, Precordillera de San Juan, Argentina. XI. Congr Geol Arg Acta 2: 61–64
Cabaleri NG, Gonzalez S, Armella C (1985) Accumulaciones arrecifales en el Ordovicico Medio — Superior de la Formación Las Aguaditas, San Juan. Reunión Com Paleontol Acta: 74–76
Cañas F, Keller M “Reefs” y “Reef Mounds” en la Formación San Juan (Precordillera Sanjuanina, Argentina): Los arrecifes más antiguos de Sudamérica. Bol Real Soc Espanol de Hist Nat (Geología), Madrid, in press
Cingolani CA, Cuerda AJ, Varela R, Schauer O (1989) Geologia de la Precordillera Occidental en la Comarca de la Sierra del Tontal, Provincia de San Juan, República Argentina. Rev Comun 40: 39–56
Cook HE (1979) Ancient continental slope sequences and their value in understanding modern slope environments. In: Doyle LJ, Pilkey OH (eds) Geology of Continental Slopes Soc Econ Paleontol Mineral Spec Publ No 27: 287–305
Cook HE, Mullins HT (1983) Basin Margin Environment. In: Scholle PA, Bebout DG, Moore CH (eds) Carbonate Depositional Environments. Am Assoc Petrol Geol Mem No 33: 539–617
Cook HE, Taylor ME (1977) Comparison of continental slope and shelf environments in the Upper Cambrian and lowest Ordovician of Nevada. In: Cook HE, Enos P (eds) Deep-water Carbonate Environments Soc Econ Paleontol Mineral Spec Publ No 25: 51–81
Cuerda AJ (1986) Graptolitos dal techo de la Formación San Juan, Precordillera de San Juan. IV. Congr Arg de Paleontol y Bioestratrigr Acta 1: 49–58
Cuerda AJ, Cingolani CA, Varela R (1983) Las graptofaunas de la Formación Los Sombreros, Ordovicico Inferior de la vertiente oriental de la Sierra dal Tontal, Precordillera de San Juan. Ameghiniana 20 (3/4): 239–260
Dalla Salda L, Cingolani CA, Varela R (1992) Early Paleozoic orogenic belts of the Andes in southwestern South America: Result of Laurentia-Gondwana collision? Geology 20: 617–620
Dalla Salda L, Dalziel IWD, Cingolani CA, Varela R Did the Taconic Appalachians continue into South America? Geology 20/12, in press
Davies GR (1977) Turbidites, debris sheets and truncation structures in Upper Paleozoic deep-water carbonates of the Sverdrup Basin, Arctic Archipelago. In: Cook HE, Enos P (eds) Deep-water Carbonate Environments. Soc Econ Paleontol Mineral Spec Publ No 25: 221–247
Eberlein S (1990) Conodontenstratigraphie und Fazies der Formation Las Aguaditas (Ordovizium/Argentinische Präkordillere). Unpubl Dipl Arb Geol Inst Erlangen: 83 pp
Einsele G (1991) Submarine mass-flow deposits and turbidites. In: Einsele G, Ricken W, Seilacher A (eds) Cycles and Events in Stratigraphy. Springer, Berlin Heidelberg New York: 313–339
Fortey RA (1984) Global earlier Ordovician transgressions and regressions and their biological implications. In: Bruton DL (ed) Aspects of the Ordovician System. Universitetsforlaget, Oslo: 37–50
Fortey RA, Bassett MG, Harper HAT, Hughes RA, Ingham JK, Molyneux SG, Owen AW Owens RM, Rushton AWA, Sheldon PR (1991) Progress and problems in the selection of stratotypes for the base of series in the Ordovician System of the historical type area in the U.K. In: Barnes CR, Williams SH (eds) Advances in Ordovician Geology. Geol Surv Can Pap No 90–9: 5–26
Furque G (1979) Descripción geológica de la hoja 18c, Jáchal (provincia de San Juan). Bol Serv Geol Nac 164: 79 pp
Furque G (1983) Descripci6n geológica de la hoja 19c, Ciénaga de Gualilán. Secret Min Bol 193: 111 pp
Gosen W von (1992) Structural evolution of the Precordillera (Argentina): the Rio San Juan section. J Struct Geol 643–667
Hallam A (1981) Facies Interpretation and the Stratigraphic Record. Freeman, Oxford: 291 pp
Hallock P, Schlager W (1986) Nutrient excess and the demise of coral reefs and carbonate platforms. Palaios 1: 389–398
Kay SM, Ramos VA, Kay R (1984) Elementos mayoritarios y trazas de las vulcanitas Ordovícícas en la Precordillera Occidental: Basaltos de rift oceánicos tempranos (?) próximos al margcn continental. — IX. Congr Geol Arg Acta 2: 48–65
Keller M, Bordonaro O. Cyclic carbonate platform evolution controlled by major regressive events: the Lower/Middle Cambrian La Laja Formation, Western Argentine Precordillera. J South Am Earth Sci, in press
Keller M, Bordonaro O. Arrecifes de estromatoporidos en el Ordovícico Inferior del Oeste Argentino y sus implicaciones paleogeográflcas. Rev Espanol Paleontol, in press
Keller M, Buggisch W, Bercowski F (1989) Facies and sedimentology of Upper Cambrian shallowing-upward cycles in the La Flecha Formation (Argentine Precordillera). Zbl Geol Paleontol 1(5/6): 999–1011
Keller M, Bordonaro O, Beresi M. The Cambrian of San Isidro, Mendoza, Argentina: facies and sedimentology at the platform slope transition. N Jb Geol Paleontol Mh, in press
Krause FF, Oldershaw AA (1979) Submarine carbonate breccia beds — a depositional model for two-layer, sediment gravity flows from the Sekmi Formation (Lower Cambrian), Mackenzie Mountains, Northwest Territories. Can J Earth Sci 16: 189–199
Lehnert O (1990) Conodontenstratigraphie und Fazies der Formation San Juan bei Niquivil (Unteres Ordoviz, Argentinien, Präkordillere). Unpubl Dipl Arb Geol Inst Erlangen: 171 pp
Loske WP (1992) Sedimentologie, Herkunft und geotektonische Entwicklung paláozoischer Gesteine der Präkordillere West-Argentiniens. Unpubl Habil Thesis Univ München: 144 pp
Mellreath IA, James NP (1984) Carbonate Slopes. In: Walker RG (ed) Facies Models. Geoscience Canada, Ottawa: 245–257
Middleton GV, Hampton MA (1976) Subaqueous sediment transport and deposition by sediment gravity flows. In: Stanley DJ, Swift DIP (eds) Marine Sediment Transport and Environmental Management. Wiley, New York: 197–218
Mullins HT, Neumann AC, Wilber RJ, Boardman MR (1987) Nodular carbonate sediment on Bahamian slopes: possible precursors to nodular limestones. I: Cant DJ, Hein FJ, (eds.) Approaches to Interpretation of Sedimentary Environments. Soc Econ Paleontol Mineral Repr Ser 11: 33–47
Nardin TR, Heinar FJ, Gorsline DS, Edwards BD (1979) A review of mass movement processes, sediment and acoustic characteristics, and contrasts in slope and base-of slope systems versus canyon — fan — basin floor systems. In: Doyle LJ, Pilkey OH (eds) Geology of Continental Slopes. Soc Econ Paleontol Mineral Spec Publ 27: 61–73
Ramos VA (1988) Late Proterozoic—Early Paleozoic of South America: a collisional history. Episodes 11: 168–173
Ramos VA, Jordan TE, Allmendinger RW, Mpodozis C, Kay SM, Cortes JM, Palma M (1986) Paleozoic terranes of the Central Argentine—Chilean Andes. Tectonics 5: 855–880
Reinhardt J (1977) Cambrian off-shelf sedimentation, Central Appalachians. In: Cook HE, Enos P (eds) Deep-water Carbonate Environments. Soc Econ Paleontol Mineral Spec Publ No 25: 83–112
Ross CA, Ross JRP (1988) Late Paleozoic transgressive-regressive deposition. In: Wilgus CK, Hastings BS, Kendall ChrGStC, Posamentier HW, Ross ChA, Van Wagoner JC (eds) Sea-Level Changes — An Integrated Approach. Soc Econ Paleontol Mineral Spec Publ No 42: 227–247
Rupke NA (1982) Deep elastic seas. In: Reading HG (ed) Sedimentary Environments and Facies. Blackwell, Oxford: 372–415
Sánchez TM, Benedetto JL, Brussa E (1991) Late Ordovician stratigraphy, paleoecology, and sea level changes in the Argentine Precordillera. In: Barnes CR, Williams SH (eds) Advances in Ordovician Geology. Geol Surv Can Pap No 90–9: 245–258
Sarg JF (1988) Carbonate sequence stratigraphy. In: Wilgus CK, Hastings BS, Kendall ChrGStC, Posamentier HW, Ross ChA, Van Wagoner JC (eds) Sea-level Changes – An Integrated Approach. Soc Econ Paleontol Mineral Spec Publ No 42: 155–181
Sarmiento GN (1986) La biozona de Amorphognathus variabilis — Eoplacognathus pseudoplanus (Conodonta), Llanvirniano Inferior, en el flanco oriental de la Sierra de Villicum. — I. J Geol Precordillera Acta: 119–123
Schlager W (1991) Sedimentology and sequence stratigraphy of reefs and carbonate platforms. Short Course Geol Vereinigung: 104 pp
Schlager W, James NP (1978) Low-magnesian calcite limestones forming at the deep-sea floor, Tongue of the Ocean, Bahamas. Sedimentology 25: 675–702
Scholle PA, Arthur MA, Ekdale AA (1983) Pelagic environments. In: Scholle PA, Bebout DG, Moore CH (eds) Carbonate Depositional Environments. Am Assoc Petrol Geol Mem No 33: 619–691
Spaletti LA, Cingolani CA, Varela R, Cuerda AJ (1989) Sediment gravity flow deposits of an Ordovician deep-sea fan system (western Precordillera, Argentina). Sedim Geol 61: 287–301
Spjeldnaes N (1961) Ordovician climatic zones. Norsk Geol Tidsskr 41: 45–77
Wächtcr J (1987) Jurassische Massflow- und Internbrekzien und ihr sedimentärtektonisches Umfeld im mittleren Abschnitt der Nördlichen Kalkalpen. Bochumer geol geotechn Arb 27: 239 pp
Wagoner JC van, Posamentier HW Mitchum RM, Vail PR, Sarg JF, Loutit TS, Hardenbol J (1988) An overview of the fundamentals of sequence stratigraphy and key definitions. In: Wilgus CK, Hastings BS, Kendall ChrGStC, Posamentier HW Ross ChA, Van Wagoner JC (eds) Sea level Changes — An Integrated Approach. Soc Econ Paleontol Mineral Spec Publ No 42: 39–45
Webby BD (1984) Ordovician reefs and climate: a review. In: Bruton GM (ed) Aspects of the Ordovician System. Universitetsforlaget, Oslo: 89–100
Wilson JL (1969) Microfacies and sedimentary structures in “deeper water” lime mudstones. In: Friedman GM (ed) Depositional Environments in Carbonate Rocks. Soc Econ Paleontol Mineral Spec Publ No 14: 4–19
Wilson JL (1975) Carbonate Facies in Geologic History. Springer, Berlin Heidelberg New York: 471 pp
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Keller, M., Eberlein, S. & Lehnert, O. Sedimentology of middle ordovician carbonates in the Argentine precordillera: evidence of regional relative sea-level changes. Geol Rundsch 82, 362–377 (1993). https://doi.org/10.1007/BF00191838
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DOI: https://doi.org/10.1007/BF00191838