Introduction to the field trip.

COLD-E-VENTGuide bookletS. CONTI, M. TAVIANI, G.B. VAIThe trips run entirely through the external part of the Northern Apennines. This part of the Northern Apennines is a NW to SE trending, NE verging thrust belt, mainly composed of Neogene to quaternary silicoclastic rocks, and having been involved in discrete, Serravallian to Middle Pleistocene deformational phases. A simplified account on Northern Apennines stratigraphy and tectonics including structural map and cross sections is attached (VAI, 1989).This booklet contains the basic informations concerning stops and transfers, and is supplemented by the following list of documents and papers.- A3 Location map and road plan of the Romagna Apennines trip (scale 1:200.000)- A3 Location map and road plan of the Modena Apennines Trip (scale 1:200.000)- A3 Northern Apennines simplified structural map and conceptual sections.- A3 Stratigraphic correlation chart of the Northern Apennines, plus A4 detail of the Romagna- Adriatic Apennines (VAI, 1992)- double A3 Geological map of the Modenese Apennine and surrounding areas (colour) (UNIVERSITY OF MODENA, GEOLOGICAL INSTITUTE, 1989)- A3 Geological map of the Romagna Apennines (colour) (LANDUZZI, 1990)- A3 Geological map of the Romagna Apennines (CAPOZZI et al., 1992)- A3 Balanced cross sections of the Romagna Apennines (LANDUZZI & CAPOZZI, 1992)G.B. VAI (1989) - A field trip guide to the Romagna Apennine geology. Boll. Soc. Pal. It., 28, 343-368.S. CONTI (1993) - Carta Geologica dell’alta Val Marecchia (Appennino tosco-marchigiano). S.EL.CA., Firenze.C. TERZI (1993) - The “Calcari a Lucina” (Lucina Limestones) of the Tuscan-Romagna Apennines as indicators of Miocene cold seep activity (northern Apennines, Italy). Giorn. Geol.,55(2), 71-81.BERTI M., CUZZANI M.G., LANDUZZI A., TAVIANI M., AHARON P. & VAI G.B. (1994) - Hydrocarbo-derived imprints in olistostromes of the Early Serravallian Marnoso-arenacea Formation, Romagna Apennines (Northern Italy). Geo-Marine Letters 14, 192-200.S. CONTI & R. GELMINI (1994) - Miocene-Pliocene tectonic phases and migration of foredeep-thrust belt system in Northern Apennines. Mem. Soc. Geol. It., 48(1)(1992), 261-274, figs.1-9, 1 pl., Roma.S. CONTI, R. GELMINI & L. PONZANA (1994) - Osservazioni preliminari sui calcari a Lucine dell'Appennino Settentrionale. Atti Soc. Nat. e Mat. di Modena, 124 (1993), 35-56, figg. 1-6, Modena.F. RICCI LUCCHI & G.B. VAI (1994) - A stratigraphic and tectonofacies frameworkof the "calcari a Lucina" in the Apennine Chain, Italy. Geo-Marine Letters, 14, 210-218.M. TAVIANI (1994) - The calcari a Lucina macrofauna reconsidered:Deep-sea faunal oases from Miocene-age cold vents in the Romagna Apennine, Italy. Geo-Marine Letters, 14, 185-191.C. TERZI, P. AHARON, F. RICCI LUCCHI & G.B. VAI (1994) - Petrography and stable isotope aspects of cold-vent activity imprinted on Miocene-age "calcari a Lucina" from Tuscan and Romagna Apennines, Italy. Geo-Marine Letters, 14, 177-184.S. CONTI, R. GELMINI, G. PONZANA & G.P. SIGHINOLFI (1996) - "Il Calcare a Lucina pomum”della Successione Epiligure dell’Appennino modenese: stratigrafia, sedimentologia e dati geochimici. Accad. Naz. Sci. Lett. Arti di Modena, Collana di Studi 15(1996) - Miscellanea Geologica, 105-139.S. CONTI (1997) - Synthetic review and geological framework of the main lucinid deposits (Italy). (this booklet)FIELD TRIP IN THE ROMAGNA APENNINESJune 24-25, 1997Leaders: A. Landuzzi, F. Ricci Lucchi, M. Taviani, G.B. Vai, P. Aharon, S. Conti.Transfer from Capaccio Centre near S. Sofia to le Caselle near M. Marino, either anticlockwise through Ridracoli Lake (drinking water reservoir of about 35 millions cubic meters) or clockwise through Poggio alla Lastra, depending on the state of unpaved road. Overview of the Alta Romagna Marnoso-arenacea (late Langhian-Serravallian) (see cross section Romagna in the attached A3 balanced cross sections sheet).STOP 1LE CASELLE OLISTOSTROME AND OLISTOLITHSLithology- extrabasinal marls, micrtitic sometimes brecciated limestones, marls with pebble-size limestone concretions.Age- (olistostrome marls) early SerravallianEnclosing formation- Marnoso-arenacea Fm (early Serravallian)Depositional tectonofacies- inner foredeepStructural setting- asymmetric recumbent synclineVenting related features-Additional informations- see Berti et al., attachedTransfer to Raggio, via S. Sofia. Overview of the Marnoso-arenacea formation (late Langhian-Serravallian) and its lateral transition to the Verghereto Marls (Serravallian-Tortonian) and S. Paolo Clays (late Tortonian-early Messinian).STOP 2CASE ROVERETI NEAR RAGGIOLithology- brecciated marly-limestones bodies within pelitic marlsEnclosing formation- S. Paolo clay member of Marnoso-arenacea Fm (Tortonian)Depositional tectonofacies- intermediate foredeepStructural setting- very close to a recent major low-angle south dipping extensional listric fault, inverting a previuos northeast verging thrust planeVenting related features-Additional informations- S. Paolo clays and Verghereto Marls are capped at the top by the allocthonous units of the Val Marecchia thrust-sheet.Transfer to Passo Carnaio (lunch stop). Panoramic view of the Ligurian basal complexes (here mainly constituted of polychromic clays) and the overlying Poggio Carnaio sandstones (late Oligocene) with the Trappole marker bed (15 m thickness) belonging to the Epiligurian Sequence. These allocthonous units can be considered a lateral appendix of the Val Marecchia sheet. The arrival time of this thrust-sheet is approximatively Tortonian marking the end of local deposition. Then the itinerary goes on towards Montepetra passing through (near Quarto) the thrust plane (marked by verticalised beds) of the Inner Marnoso-arenacea Unit (Langhian-Serravallian) over the Outer Marnoso-arenacea Unit (late Serravallian-Tortonian) (see CONTI & GELMINI, 1994 enclosed paper). In the proximity of the Montepetra tunnel, it is possible to observe the vertical transition from basin plain and fan fringe pelitic-sandy deposits into sand lobes and channelised proximal facies (Outer Marnoso-arenacea of Tortonian-early Messinian age).STOP 3 MONTEPETRA (LUCINID DEPOSITS AND CHAOTIC LEVELS)Lithology- dark biomicritic marly limestones very rich in disarticulated bivalves, brecciated marly limestones, calcarenitic limestones with articulated lucinids.Enclosing formation- Ghioli di letto mudstones (late Tortonian) representing the pelitic closure of the Outer Marnoso-arenacea Unit.Depositional tectonofacies- slope marls of intermediate foredeep.Structural setting- strata gently dipping towards ESE and close to the thrust of the allocthnous Val Marecchia sheet over the early pliocenic Argille Azzurre (see CONTI, 1993 enclosed geological map).Venting related features- Additional informations- The lucinid blocks (up to 8-10 m thick) are probably reworked, because they are intercalated within a resedimented horizon extending from Mercato Saraceno to upper Marecchia Valley (Petrella Massana). This horizon (late Tortonian-early Messinian) is made up of intraformational slumps, ligurian olistostromes, ligurian and epiligurian olistoliths and channelised resedimented sanstones (S. Agata Feltria sandstones).Downhill return to Sarsina; before arriving to the small town facultative stop (left roadcut). The outcrop shows the typical structures (diffuse lamination, clay chips, basal scours, amalgamation surfaces, convolutions, dishes, pillars and pipes) of the inner fan turbidites of the Marnoso arenacea Fm (Tortonian-early Messinia). Arrive to Sarsina (birthplace of the latin comedy writer T.M. Plautus) in order to visit the cathedral and roman relics of the grave and of the ancient foro.Back to Ridracoli Lake-Capaccio center for dinner and overnight accomodation.STOP 4Le CollineSTOP 5 Ca Piantè-bivio CastelnuovoSTOP 6 PietralungaFIELD TRIP IN THE MODENA FOOTHILLSJune 26 1997Leaders S. Conti, M. TavianiTransfer to Sassuolo, “capital” of italian poterries and then to the terracced deposits (Quaternary) of the Secchia River, the neoautocthonous pliocenic deposits and the basal part (late Eocene-early Miocene) of the Epiligurian Sequence.After going through the Bismantova Formation (middle Miocene) it arrives to the next stops which are representative of the lucinid deposits occurring in the Epiligurian satellite basins.STOP 7POGGIO DI MONTEBARANZONE (SARSETTA) (PANORAMIC VIEW OF PRIMARY LUCINID DEPOSITS)Outcrop description- From the base to the top: 1) pelitic marls interbedded with scattered marly calcareous lenses very rich in bivalves (mainly lucinids) (late Serravallian); 2) resedimented sandstones with coquina debris (tempestites ?) interbedded with fossiliferous pelitic marls lacking of lucinids (early Tortonian); 3) medium to coarse grained turbiditic sandstones with thin levels of debrites (Montebaranzone sandstones - Tortonian) 4) polygenic clayey breccias (Montebaranzone-Montardone olistostrome), derived from submarine mud flows and debris flows detached from Ligurian formations (Tortonian). Stratigraphy- Termina Formation (late Serravallian-Tortonian) Environment- outer shelf, inner slope ? Fossil assemblage- (from literature) Lucina hornesii, L. delbosii (=pomum =appenninica), Cypraea amygdalum, Fusus glomus, F. rostratus, Modiola subcarinata, Ostrea pusilla, Vermetus intortus, Ranella reticulata, Trochus rotelaris, T. magus, Petricula lithophagaVenting related features- Structural setting- northern limb of the Montebaranzone-Montardone synclineGeological notes- Primary position of the lucinid lenses, as testified by the gradual transition to the surrounding sediments, the concordance of the stratification attitudes and last, but not least, by the articulated and sometimes still in situ lucinids.Transfer to Monteardone passing through the Coscogno tectonic melange made up of undifferentiated basal complexes (mainly Scabiazza sandstones and polychromic clays) and ophiolites (Varana) and carrying on its top the Mt. Cassio Flysch (late Cretaceous).STOP 8 SASSO DELLE STREGHE (ROCCA S. MARIA), (THE LUCINID HORIZON)This stop is subdivided into two parts:1) LE PRADE (PANORAMIC VIEW OF THE LUCINID HORIZON)In order to observe the vertical and lateral development of lucinid pseudobioherms passing laterally to the Termina Marls. Outcrop description- marly calcareous lens-like and columnar decametric level very rich in bivalves (mainly lucinids and vesicomyids) gradually passing to poorly stratified pelitic marls (late Serravallian). At the top the Montebaranzone sanstones and, also laterally by tectonic contact, the Montebaranzone-Montardone olistostrome (both described in the previous stop).Structural setting- southern limb of the Montebaranzone-Montardone syncline2) SASSO DELLE STREGHE (better known in the past as “Rock of the Clams”) (CLOSE OBSERVATION)Lithology- biomicritic marly limestones, calcarenitic limestones, brecciated limestones with abundant ligurian clasts.Stratigraphy- Termina Formation (late Serravallian-Tortonian) Environment- outer shelf, inner slope ? (from the palaeontological literature)Venting related features- Geological notes- Primary position of the lucinid lenses very rich in articulated and sometimes still in situ lucinids, secondary position for the breccias, which are sometimes characterized by disarticulated bivalves.STOP 9 (facultative stop depending on the available time)BORRA DI POGGIO ANDREOTTI Lithology- Isolated block of marly-limestones, calcarenitic limestones and brecciated limestones.Outcrop description- The poor exposure does not permit a precise determination of the geological conditions. Possibility to have a big collection of lucinid bivalves.Stratigraphy of the enclosing sediments- Termina Formation (late Serravallian-Tortonian). The block is probably correlable to the Rocca S. Maria horizon. Visit to the preromanic church of Rocca S. Maria (cultural site) and then lunch time at the Salse di Nirano mud volcanoes: a good example of modern fluid venting.Return to Modena (Dipartimento di Scienze della Terra, Largo S. Eufemia 19) for additional presentation on cold seepage and general discussion on cold venting and associated products.