The Triassic and Jurassic Sedimentary Cycles in Central Sardinia
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Geological Field Trips Società Geologica Italiana 2016 Vol. 8 (1.1) ISPRA Istituto Superiore per la Protezione e la Ricerca Ambientale SERVIZIO GEOLOGICO D’ITALIA Organo Cartografico dello Stato (legge N°68 del 2-2-1960) Dipartimento Difesa del Suolo ISSN: 2038-4947 The Triassic and Jurassic sedimentary cycles in Central Sardinia: stratigraphy, depositional environment and relationship between tectonics and sedimentation 85° Congresso Nazionale della Società Geologica Italiana - Sassari, 2008 DOI: 10.3301/GFT.2016.01 The Triassic and Jurassic sedimentary cycles in Central Sardinia: stratigraphy, depositional environment and relationship between tectonics and sedimentation L. G. Costamagna - S. Barca GFT - Geological Field Trips geological fieldtrips2016-8(1.1) Periodico semestrale del Servizio Geologico d'Italia - ISPRA e della Società Geologica Italiana Geol.F.Trips, Vol.8 No.1.1 (2016), 78 pp., 54 figs. (DOI 10.3301/GFT.2016.01) The Triassic and Jurassic sedimentary cycles in Central Sardinia: stratigraphy, depositional environment and relationship between tectonics and sedimentation 85° Congresso Nazionale della Società Geologica Italiana, Sassari 6-8 settembre 2010 Luca G. Costamagna*, Sebastiano Barca** * Dipartimento di Scienze Chimiche e Geologiche, Via Trentino, 51 - 09127, Cagliari (Italy) ** Via P. Sarpi, 18 - 09131, Cagliari (Italy) Corresponding Author e-mail address: [email protected] Responsible Director Claudio Campobasso (ISPRA-Roma) Editorial Board Editor in Chief Gloria Ciarapica (SGI-Perugia) M. Balini, G. Barrocu, C. Bartolini, 2 Editorial Responsible D. Bernoulli, F. Calamita, B. Capaccioni, Maria Letizia Pampaloni (ISPRA-Roma) W. Cavazza, F.L. Chiocci, R. Compagnoni, D. Cosentino, Technical Editor S. Critelli, G.V. Dal Piaz, C. D'Ambrogi, Mauro Roma (ISPRA-Roma) P. Di Stefano, C. Doglioni, E. Erba, publishing group R. Fantoni, P. Gianolla, L. Guerrieri, Editorial Manager M. Mellini, S. Milli, M. Pantaloni, Maria Luisa Vatovec (ISPRA-Roma) V. Pascucci, L. Passeri, A. Peccerillo, Convention Responsible L. Pomar, P. Ronchi, B.C. Schreiber, Anna Rosa Scalise (ISPRA-Roma) L. Simone, I. Spalla, L.H. Tanner, Alessandro Zuccari (SGI-Roma) C. Venturini, G. Zuffa. ISSN: 2038-4947 [online] http://www.isprambiente.gov.it/it/pubblicazioni/periodici-tecnici/geological-field-trips The Geological Survey of Italy, the Società Geologica Italiana and the Editorial group are not responsible for the ideas, opinions and contents of the guides published; the Authors of each paper are responsible for the ideas, opinions and contents published. Il Servizio Geologico d’Italia, la Società Geologica Italiana e il Gruppo editoriale non sono responsabili delle opinioni espresse e delle affermazioni pubblicate nella guida; l’Autore/i è/sono il/i solo/i responsabile/i. DOI: 10.3301/GFT.2016.01 The Triassic and Jurassic sedimentary cycles in Central Sardinia: stratigraphy, depositional environment and relationship between tectonics and sedimentation L. G. Costamagna - S. Barca geological fieldtrips2016-8(1.1) INDEX Information Abstract .......................................................................5 2.2.2. Monte Maiore fm.: homoclinal ramp Riassunto .....................................................................6 sub-environments .....................................................20 Safety/Hospitals ............................................................8 2.3 First Mesozoic sedimentary cycle in Central Sardinia: Service stations/Accommodations ....................................8 some remarks .............................................................22 General information about the Itinerary .............................9 3. Post-variscan geological evolution: Jurassic ..................24 Recommended cartography ...........................................10 3.1. Jurassic successions: regional frame and stratigraphy ..24 3 3.1.1. Genna Selole fm. ........................................27 Excursion notes 3.1.2. Dorgali fm. ................................................32 3.1.3. Genna Silana fm. ........................................33 General framework ...................................................12 3.1.4. Definition of the Baunei group .......................33 The Tacchi area (Central Sardinia): geomorphological and 3.2 Depositional environment of the Jurassic units ............34 paleogeographical premise ............................................12 3.2.1. Baunei group, Genna Selole fm.: Geological setting .....................................................14 alluvial to deltaic (?) system ..................................34 1. Variscan Paleozoic Basement and 3.2.2 Baunei group, Dorgali fm.: Permo-Carboniferous covers ..........................................14 tidal flat and inner ramp lagoon ..............................36 2. Post-variscan geological evolution: Triassic ...................15 3.2.3 Baunei group, Genna Silana fm.: 2.1. Triassic successions: regional frame and stratigraphy ..15 oolitic margin with patch-reefs ...............................36 index 2.1.1. Escalaplano Fm. ............................................16 3.2.4. Paleogeographic and geodynamic meaning of 2.1.2. Monte Maiore fm. ........................................18 the Baunei group .................................................37 2.2 Depositional environment of the Triassic succession .....20 3.3. The Jurassic succession: 2.2.1 Escalaplano Fm.: alluvial fans and mudflats .....20 second Mesozoic sedimentary cycle, conclusions ...............38 DOI: 10.3301/GFT.2016.01 The Triassic and Jurassic sedimentary cycles in Central Sardinia: stratigraphy, depositional environment and relationship between tectonics and sedimentation L. G. Costamagna - S. Barca geological fieldtrips2016-8(1.1) Itinerary Day 1 - From Cagliari to Jerzu (OG) ...........................41 Day 2: from Jerzu to Osini .........................................64 STOP 1 - Bruncu su Para (Orroli): general features of STOP 8 - Pitzu S. Antonio (Tertenia Tacco): the Escalaplano Fm. and Monte Maiore fm. .......................44 sedimentological features of the Middle Jurassic STOP 2 - Bruncu Geroni (Orroli): algae in the yellow transgression over the Variscan basement .......................64 dolostones member of the Monte Maiore fm. and Stop 8b - Ungul'e Ferru: accretion clinoforms in the passage to the Tertiary deposits .....................................46 Dorgali fm. ..................................................................67 STOP 3 - Piccheri (Orroli): Middle Triassic/ Middle Jurassic STOP 9 - Monte Lumburau (Jerzu Tacco): 4 unconformity and general features of the Genna Selole fm. ..48 laterites(“Ferro dei Tacchi”) at the base of the STOP 4 – Escalaplano (Escalaplano Tacco): type section and Middle Jurassic transgression .........................................68 sedimentological features of the Escalaplano Fm. ...................51 STOP 10 - Bruncu Matzeu (Ulassai Tacco): synsedimentary Stop 4b - Ponte Tradala - Features of the transition from the extensional tectonics, transitional depositional environments and Genna Selole fm. to the Dorgali fm. ................................55 early karstic cycles at the Genna Selole fm./Dorgali fm. STOP 5 - Arcu de Is Fronestas (Escalaplano Tacco): transition ....................................................................69 unconformity between the Escalaplano Fm. and STOP 11 - Grutta Orroli and Punta su Scrau (Osini Tacco): the Genna Selole fm. ....................................................55 oolitic grainstones, patch reefs and oncoids of the STOP 6 - Sa Teria (Perdasdefogu Tacco): sedimentologica Genna Silana fm. .........................................................71 l features of the upper Genna Selole fm. and Stop 11a - Osini Tacco: small patch reef in the Genna Silana fm. ..71 the lower Dorgali fm. ....................................................59 Stop 11b - Punta Su Scrau: index STOP 7 - Serra Is Arangius (Perdasdefogu Tacco): oncolitic floatstones in the Genna Silana fm. .....................71 parastratotype and sedimentological features of the Genna Selole fm. .........................................................61 References ................................................................75 DOI: 10.3301/GFT.2016.01 The Triassic and Jurassic sedimentary cycles in Central Sardinia: stratigraphy, depositional environment and relationship between tectonics and sedimentation L. G. Costamagna - S. Barca Abstract geological fieldtrips2016-8(1.1) This field trip presents a general overview of the stratigraphical, sedimentological and paleogeographic evolution of the Middle Triassic and Middle Jurassic successions in che Central Sardinia Tacchi area (Gerrei, Sarcidano, Barbagia, Ogliastra). These successions are divided by an unconformity and are both laid down under active extensional tectonics conditions. The Triassic Eastern Sardinia succession belongs to the Germanic Triassic Domain (Buntsandstein and Muschelkalk facies group), so showing strict affinites with the Iberian and Mid-European successions. It is featured by transgressive siliciclastic to carbonate deposits not more than few tens of meters thick: they represent the evolution from a continental, middle to low-energy environment to a restricted shallow marine one. This succession deposited along the stretching southern margin of the Paleo-European Plate under a hot- arid climate: it represents the last remain of the first Mesozoic depositional cycle in the area. The Middle Triassic deposits