http://hdl.handle.net/2122/235 Sun, 19 May 2013 17:30:40 GMT 2013-05-19T17:30:40Z http://hdl.handle.net/2122/8555 Title: A ~125° post-early Serravallian counterclockwise rotation of the Gorgoglione Formation (Southern Apennines, Italy): New constraints for the formation of the Calabrian Arc Authors: Maffione, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cascella, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Longhitano, S. G.; Department of Geological Sciences, Università della Basilicata, Potenza, Italy; Chiarella, D.; Department of Geological Sciences, Università della Basilicata, Potenza, Italy Abstract: The Southern Apennines, Calabro-Peloritane block, and Sicilian Maghrebides form a ~700 km long orogenic bend, known as Calabrian Arc (Cifelli et al., 2007). The bending of this orogenic system was realized progressively through opposite-sense rotation of the two limbs, counterclockwise (CCW) in the Southern Apennines and clockwise (CW) in the Sicilian Maghrebides, synchronous to the Miocene-to-Present opening of the Tyrrhenian Sea. Despite the wealth of paleomagnetic data from the Southern Apennines, the main Miocene rotational phase still remains poorly constrained in time and, more importantly, data from the most internal paleogeographic domains of the belt are completely lacking. The Gorgoglione Formation, a middle Miocene piggy-back deposit of the Southern Apennines, unconformably resting over the internal Sicilide Unit, offers the unique opportunity to document the deformation pattern of the most internal units, and reconstruct the incipient tectonic phases leading to the formation of the Calabrian Arc. New paleomagnetic and biostratigraphic data from the Gorgoglione Fm. reveal a post-early Serravallian ~125° CCW rotation with respect to stable Africa. Such a large rotation, affecting the Gorgoglione Fm. (and consequently the underneath allochthonous Sicilide nappe) exceeds by ~45° the maximum mean CCW rotation previously reported for the Southern Apennines. We propose that the additional ~45° CCW rotation measured in the Sicilide Unit is the result of an earlier, late Miocene phase of deformation related to the onset of the Tyrrhenian Sea opening and affecting the most internal paleogeographic domains of the Southern Apennines. Our reconstructed tectonic scenario confirms and emphasizes the central role of the Ionian slab in the geodynamic evolution of the central Mediterranean. Sun, 31 Mar 2013 22:00:00 GMT http://hdl.handle.net/2122/8555 2013-03-31T22:00:00Z http://hdl.handle.net/2122/8521 Title: Understanding progressive-arc- and strike-slip-related rotations in curve-shaped orogenic belts: The case of the Olevano-Antrodoco-Sibillini thrust (Northern Apennines, Italy) Authors: Turtù, A.; Dipartimento di Ingegneria e Geologia, Università “G. D’Annunzio” di Chieti-Pescara, Chieti, Italy.; Satolli, S.; Dipartimento di Ingegneria e Geologia, Università “G. D’Annunzio” di Chieti-Pescara, Chieti, Italy.; Maniscalco, R.; Dipartimento di Scienze Biologiche, Geologiche e Ambientali, Università degli Studi di Catania, Catania, Italy.; Calamita, F.; Dipartimento di Ingegneria e Geologia, Università “G. D’Annunzio” di Chieti-Pescara, Chieti, Italy.; Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: We report on a paleomagnetic study of the southern sector of the Olevano-Antrodoco-Sibillini (OAS) thrust front, which corresponds to the southern limb of the Northern Apennines (Italy) orogenic salient. A lively debate has developed regarding the oroclinal/progressive-arc versus non-rotational nature of the OAS, which has been alternatively interpreted as a dextral strike-slip fault, dextral transpressive fault, or frontal to oblique ramp that reactivated pre-existing Jurassic normal faults. Here, we document the paleomagnetism, integrated with biostratigraphic and structural data, of 52 new sites from both the OAS hanging wall and footwall. On the basis of 39 retained sites, we find a peculiar pattern of tectonic rotations along the OAS thrust that evidences four rotational domains. The thrust footwall is characterized by a southern domain that undergoes an approximately 30 counterclockwise rotation with respect to the stable foreland, and an approximately nonrotated domain. The data from the hanging wall indicate the occurrence of a dextral strike-slip component along the southern sector of the OAS thrust supported by a strong clockwise rotation close to the NE-SW lateral ramp, which rapidly fades 1 km from the thrust front. A slight but significant CW rotation observed in the remaining sites from the hanging wall confirms the progressive nature of the OAS, and its structural position as the southern limb of the Northern Apennines salient. Our detailed paleomagnetic study is crucial in discriminating between progressive-arc- and strike-slip-related components in the main curved orogenic front of the Northern Apennines. Wed, 06 Feb 2013 23:00:00 GMT http://hdl.handle.net/2122/8521 2013-02-06T23:00:00Z http://hdl.handle.net/2122/8267 Title: Searching for single domain magnetite in the “pseudo-single-domain” sedimentary haystack: Implications of biogenic magnetite preservation for sediment magnetism and relative paleointensity determinations Authors: Roberts, A. P.; National Oceanography Centre, University of Southampton, Southampton, UK.; Chang, L.; National Oceanography Centre, University of Southampton, Southampton, UK.; Heslop, D.; Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia.; Florindo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Larrasoaña, J. C.; Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia. Abstract: Magnetic hysteresis measurements of sediments have resulted in widespread reporting of “pseudo-single-domain”-like magnetic properties. In contrast, the ideal single domain (SD) properties that would be expected to be responsible for high quality paleomagnetic records are rare. Determining whether SD particles are rare or common in sediments requires application of techniques that enable discrimination among different magnetic components in a sediment. We apply a range of such techniques and find that SD particles are much more common than has been reported in the literature and that magnetite magnetofossils (the inorganic remains of magnetotactic bacteria) are widely preserved at depth in a range of sediment types, including biogenic pelagic carbonates, lacustrine and marine clays, and possibly even in glaci-marine sediments. Thus, instead of being rarely preserved in the geological record, we find that magnetofossils are widespread. This observation has important implications for our understanding of how sediments become magnetized and highlights the need to develop a more robust basis for understanding how biogenic magnetite contributes to the magnetization of sediments. Magnetofossils also have grain sizes that are substantially smaller than the 1–15 mm size range for which there is reasonable empirical support for relative paleointensity studies. The different magnetic response of coexisting fine biogenic and coarser lithogenic particles is likely to complicate relative paleointensity studies. This issue needs much closer attention. Despite the fact that sediments have been subjected to paleomagnetic investigation for over 60 years, much remains to be understood about how they become magnetized. Tue, 21 Aug 2012 22:00:00 GMT http://hdl.handle.net/2122/8267 2012-08-21T22:00:00Z http://hdl.handle.net/2122/8162 Title: Neogene tectonic and climatic evolution of the Western Ross Sea, Antarctica — Chronology of events from the AND-1B drill hole Authors: Wilson, G. S.; Department of Marine Science, University of Otago, PO Box 56, Dunedin, New Zealand; Levy, R. H.; GNS Science, PO Box 30‐368, Lower Hutt, New Zealand; Naish, T. R.; Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, New Zealand; Powell, R. D.; Department of Geology & Environmental Geosciences, Northern Illinois University, DeKalb, IL 60115, USA; Florindo, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Ohneiser, C.; Department of Geology, University of Otago, PO Box 56, Dunedin, New Zealand; Sagnotti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Winter, D. M.; ANDRILL Science Management Office, Department of Geosciences, University of Nebraska-Lincoln, Lincoln, NE 68588‐0340, USA; Cody, R.; Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, New Zealand; Henrys, S.; GNS Science, PO Box 30‐368, Lower Hutt, New Zealand; Ross, J.; New Mexico Institute of Mining & Technology, Earth & Environmental Sciences, Socorro, NM 87801, USA; Krissek, L.; Byrd Polar Research Centre, The Ohio State University, Columbus, OH 43210, USA; Niessen, F.; Alfred Wegener Institute, Department of Geosciences, Postfach 12 01 6, Am Alten Hafen 26, D-27515, Bremerhaven, Germany; Pompillio, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia; Scherer, R.; Department of Geology & Environmental Geosciences, Northern Illinois University, DeKalb, IL 60115, USA; Alloway, B. V.; Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, New Zealand; Barrett, P. J.; Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, New Zealand; Brachfeld, S.; Department of Earth and Environmental Studies, Montclair State University, Montclair, NJ 07043, USA; Browne, G.; GNS Science, PO Box 30‐368, Lower Hutt, New Zealand; Carter, L.; Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, New Zealand; Cowan, E.; Department of Geology, Appalachian State University, Boone, NC 28608‐2067, USA; Crampton, J.; GNS Science, PO Box 30‐368, Lower Hutt, New Zealand; DeConto, R. M.; Department of Geosciences, University of Massachusetts, Amherst, MA 01003‐9297, USA; Dunbar, G.; Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, New Zealand; Dunbar, N.; Department of Marine Science, University of Otago, PO Box 56, Dunedin, New Zealand; Dunbar, R.; Department of Environmental Earth System Sciences, School of Earth Sciences, Stanford University, Stanford, CA 94305, USA; von Eynatten, H.; Department of Sedimentology and Environmental Geology, Geoscience Center Göttingen (GZG), Goldschmidtstrasse 3, Göttingen, Germany; Gebhardt, C.; Alfred Wegener Institute, Department of Geosciences, Postfach 12 01 6, Am Alten Hafen 26, D-27515, Bremerhaven, Germany; Giorgetti, G.; Dipartimento di Scienze della Terra, Universita di Sienna, Via Laterina 8, I-53100, Sienna, Italy; Graham, I.; GNS Science, PO Box 30‐368, Lower Hutt, New Zealand; Hannah, M.; Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, New Zealand; Hansaraj, D.; Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, New Zealand; Harwood, D. M.; ANDRILL Science Management Office, Department of Geosciences, University of Nebraska-Lincoln, Lincoln, NE 68588‐0340, USA; Hinnov, L.; Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218, USA; Jarrard, R. D.; Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, USA; Joseph, L.; Environmental Studies Program, Ursinus College, Collegeville, PA 19426, USA; Kominz, M.; Department of Geology, Western Michigan University, Kalamazoo, MI 49008, USA; Kuhn, G.; Alfred Wegener Institute, Department of Geosciences, Postfach 12 01 6, Am Alten Hafen 26, D-27515, Bremerhaven, Germany; Kyle, P.; New Mexico Institute of Mining & Technology, Earth & Environmental Sciences, Socorro, NM 87801, USA; Läufer, A.; Federal Institute for Geosciences & Natural Resources, BGR, Stilleweg 2, D-30655 Hannover, Germany; McIntosh, W. C.; New Mexico Institute of Mining & Technology, Earth & Environmental Sciences, Socorro, NM 87801, USA; McKay, R.; Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, New Zealand; Maffioli, P.; Università Milano-Bicocca, Dipartimento di Scienze Geologiche e Geotecnologie, Piazza della Scienza 4, I-20126 Milano, Italy; Magens, D.; Alfred Wegener Institute, Department of Geosciences, Postfach 12 01 6, Am Alten Hafen 26, D-27515, Bremerhaven, Germany; Millan, C.; Byrd Polar Research Centre, The Ohio State University, Columbus, OH 43210, USA; Monien, D.; Alfred Wegener Institute, Department of Geosciences, Postfach 12 01 6, Am Alten Hafen 26, D-27515, Bremerhaven, Germany; Morin, R.; US Geological Survey, Mail Stop 403, Denver Federal Center, Denver, CO 80225, USA; Paulsen, T.; Department of Geology, University of Wisconsin, Oshkosh, 800 WI 54901, USA; Persico, D.; Departimento di Scienze della Terra, Universita di Parma, Parco Aeres delle Scienze, 157 Parma, Italy; Pollard, D.; Earth and Environmental Systems Institute, 2217 Earth-Engineering Science Bldg, University Park, PA 16802, USA; Raine, J. I.; GNS Science, PO Box 30‐368, Lower Hutt, New Zealand; Riesselman, C.; Department of Marine Science, University of Otago, PO Box 56, Dunedin, New Zealand; Sandroni, S.; Dipartimento di Scienze della Terra, Universita di Sienna, Via Laterina 8, I-53100, Sienna, Italy; Schmitt, D.; Department of Marine Science, University of Otago, PO Box 56, Dunedin, New Zealand; Sjunneskog, C.; Antarctic Marine Geology Research Facility, Department of Geology, Florida State University, Tallahassee, FL 32306, USA; Strong, C. P.; GNS Science, PO Box 30‐368, Lower Hutt, New Zealand; Talarico, F.; Dipartimento di Scienze della Terra, Universita di Sienna, Via Laterina 8, I-53100, Sienna, Italy; Taviani, M.; CNR, ISMAR — Bologna, Via Gobetti 101, I-40129 Bologna, Italy; Villa, G.; Departimento di Scienze della Terra, Universita di Parma, Parco Aeres delle Scienze, 157 Parma, Italy; Vogel, S.; Department of Geology & Environmental Geosciences, Northern Illinois University, DeKalb, IL 60115, USA; Wilch, T.; Albion College, Department of Geology, Albion, MI 49224, USA; Williams, T.; Columbia University, Lamont-Doherty Earth Observatory, Palisades, NY 10964, USA; Wilson, T. J.; Byrd Polar Research Centre, The Ohio State University, Columbus, OH 43210, USA; Wise, S.; Antarctic Marine Geology Research Facility, Department of Geology, Florida State University, Tallahassee, FL 32306, USA Abstract: Stratigraphic drilling from the McMurdo Ice Shelf in the 2006/2007 austral summer recovered a 1284.87 m sedimentary succession from beneath the sea floor. Key age data for the core include magnetic polarity stratigraphy for the entire succession, diatom biostratigraphy for the upper 600 m and 40Ar/39Ar ages for in-situ volcanic deposits as well as reworked volcanic clasts. A vertical seismic profile for the drill hole allows correlation between the drill hole and a regional seismic network and inference of age constraint by correlation with well‐dated regional volcanic events through direct recognition of interlayered volcanic deposits as well as by inference from flexural loading of pre‐existing strata. The combined age model implies relatively rapid (1 m/2–5 ky) accumulation of sediment punctuated by hiatuses, which account for approximately 50% of the record. Three of the longer hiatuses coincide with basin‐wide seismic reflectors and, along with two thick volcanic intervals, they subdivide the succession into seven chronostratigraphic intervals with characteristic facies: 1. The base of the cored succession (1275–1220 mbsf) comprises middle Miocene volcaniclastic sandstone dated at approx 13.5 Ma by several reworked volcanic clasts; 2. A late-Miocene sub-polar orbitally controlled glacial–interglacial succession (1220–760 mbsf) bounded by two unconformities correlated with basin‐wide reflectors associated with early development of the terror rift; 3. A late Miocene volcanigenic succession (760–596 mbsf) terminating with a ~1 my hiatus at 596.35 mbsf which spans the Miocene–Pliocene boundary and is not recognised in regional seismic data; 4. An early Pliocene obliquity-controlled alternating diamictite and diatomite glacial–interglacial succession(590–440 mbsf), separated from; 5. A late Pliocene obliquity-controlled alternating diamictite and diatomite glacial–interglacial succession (440–150 mbsf) by a 750 ky unconformity interpreted to represent a major sequence boundary at other locations; 6. An early Pleistocene interbedded volcanic, diamictite and diatomite succession (150–80 mbsf), and; 7. A late Pleistocene glacigene succession (80–0 mbsf) comprising diamictite dominated sedimentary cycles deposited in a polar environment. Sun, 30 Sep 2012 22:00:00 GMT http://hdl.handle.net/2122/8162 2012-09-30T22:00:00Z http://hdl.handle.net/2122/8127 Title: Inconsistent magnetic polarities in magnetite-and greigite-bearing sediments: Understanding complex magnetizations in the late Messinian in the Adana Basin (southern Turkey) Authors: Lucifora, S.; Dipartimento di Scienze Geologiche, Università Roma Tre, Largo San Leonardo Murialdo 1, IT-00146 Rome, Italy; Cifelli, F.; Dipartimento di Scienze Geologiche, Università Roma Tre, Largo San Leonardo Murialdo 1, IT-00146 Rome, Italy; Mattei, M.; Dipartimento di Scienze Geologiche, Università Roma Tre, Largo San Leonardo Murialdo 1, IT-00146 Rome, Italy; Sagnotti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cosentino, D.; Dipartimento di Scienze Geologiche, Università Roma Tre, Largo San Leonardo Murialdo 1, IT-00146 Rome, Italy; Roberts, A. P.; Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia Abstract: We present paleomagnetic, rock magnetic and scanning electron microscope data from three upper Messinian stratigraphic sections from the Adana Basin (southern Turkey). The collected samples are from fine-grained units, which were deposited during the Messinian Salinity Crisis (within subchron C3r). Paleomagnetic results reveal an inconsistent polarity record, related to a mixture of magnetite and greigite that hinders determination of a reliable magnetostratigraphy. Three classes of samples are recognized on the basis of paleomagnetic results. The first is characterized by a single magnetization component, with normal polarity, that is stable up to 530–580 C and is carried by magnetite. The second is characterized by a single magnetization component, with reversed polarity, that is stable up to 330–420 C. This magnetization is due to greigite, which developed after formation of slumps and before tectonic tilting of the studied successions. The third is characterized by reversed polarity, which is stable up to 530–580 C. We interpret this component as a primary magnetization carried by fine-grained and magnetically stable detrital magnetite. Results indicate that in the Adana Basin the assumption that a primary magnetization is carried by magnetite, and a magnetic overprint carried by greigite, does not hold because a late magnetic overprint has also been found for magnetite-bearing samples. Our data illustrate the complexity of magnetostratigraphic reconstructions in successions characterized by variable mixtures of magnetic minerals with different magnetic stability that formed at different stages. We demonstrate the need to perform detailed magnetic mineralogy analyses when conducting magnetostratigraphic studies of clay-rich sediments from marine or lacustrine environments. Thu, 04 Oct 2012 22:00:00 GMT http://hdl.handle.net/2122/8127 2012-10-04T22:00:00Z http://hdl.handle.net/2122/8020 Title: The diversity of sauropod dinosaurs and their first taxonomic succession from the latest Cretaceous of southwestern Europe: Clues to demise and extinction Authors: Vila, B.; Paleontología, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain; Galobart, À.; Institut Català de Paleontologia Miquel Crusafont, Carrer Escola Industrial, 23, 08201 Sabadell, Barcelona, Catalonia, Spain; Canudo, J. I.; Paleontología, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza, Spain; Le Loeuff, J.; Musée des Dinosaures, 11260 Espéraza, France; Dinarès-Turell, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Riera, V.; Departament de Geologia, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Catalonia, Spain; Oms, O.; Departament de Geologia, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Barcelona, Catalonia, Spain; Tortosa, T.; Muséum d'Histoire Naturelle d'Aix-en-Provence, 13100 Aix-en-Provence, France; Gaete, R.; Museu de la Conca Dellà, C/ del Museu 4, 25650 Isona i Conca Dellà, Lleida, Catalonia, Spain Abstract: Southwestern Europe is a key setting to evaluate the diversity of non-avian dinosaurs before the end of the Cretaceous (below the K–Pg boundary). The ancient Ibero-Armorican Island, encompassing the current regions of North-East Iberia and South France, provides a substantial record of sauropod fossils. The study of multiple sauropod femora from localities where upper Campanian to uppermost Maastrichtian successions are both exposed, together with the integration of the information gathered from previously known localities has allowed the biodiversity of sauropods to be reassessed within a precise and clear chronostratigraphic framework. From the studied sample several titanosaur forms have been distinguished including a gracile and small-sized titanosaur (Lirainosaurus astibiae), a robust medium-sized titanosaur (Ampelosaurus atacis), a gracile medium-sized titanosaur (Atsinganosaurus velauciensis), and five other indeterminate but distinct titanosaurs, which span the late Campanian through the entire Maastrichtian. The youngest of these occurs in the uppermost part of palaeomagnetic chron C30n in the latest Maastrichtian (~0.4–1 Ma before the K–Pg boundary), representing the youngest sauropod yet documented in Eurasia. The pattern of diversity on the Ibero-Armorican Island rules out a decline in sauropod diversity at the very end of the Cretaceous. As with other regions during the late Cretaceous, the abundance and quality of the sauropod fossil record is probably influenced by multiple biases (sampling, ecological, and environmental). Fri, 14 Sep 2012 22:00:00 GMT http://hdl.handle.net/2122/8020 2012-09-14T22:00:00Z http://hdl.handle.net/2122/8009 Title: Paleomagnetic secular variation at the Azores during the last 3 ka Authors: Di Chiara, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Porreca, M.; Centro de Vulcanologia e Avaliação de Riscos Geológicos, Universidade dos Açores, Ponta Delgada, Portugal. Abstract: We report on 33 new paleomagnetic directions obtained from 16 lava flows emplaced in the last 3 ka on São Miguel, the largest island of the Azores. The data provide 27 well-dated directions from historical or 14C dated flows which, together with 6 directions previously gathered from the same flows by Johnson et al. (1998), yield the first paleomagnetic directional record of the last 3 ka from the Atlantic Ocean. Within-flow directions are consistent, suggesting that inclination swings from 60 to 25 and declination changes between 10 to 20 reflect variations in the geomagnetic field over the last 3 ka. To a first approximation, the declination record is consistent with predictions from CALS3k.4 and gufm1 global field models. Conversely, inclination values are lower than model predictions at two different ages: 1) four sites from the 1652 AD flow yield I = 48 instead of I = 63 predicted by gufm1; 2) data from several flows nicely mimic the inclination minimum of 800–1400 AD, but inclination values are lower by 10 than CALS3k.4 model predictions. By interpolating a cubic spline fit on declination / inclination versus age data, we tentatively infer the directional evolution of the geomagnetic field at the Azores from 1000 BC to 1600 AD. The obtained curve shows three tracks in virtual overlap during the 1000–800 BC, 800–500 BC, and 400–700 AD time spans. Wed, 11 Jul 2012 22:00:00 GMT http://hdl.handle.net/2122/8009 2012-07-11T22:00:00Z http://hdl.handle.net/2122/7907 Title: Magnetic fabric of Pleistocene continental clays from the hanging-wall of an active low-angle normal fault (Altotiberina Fault, Italy) Authors: Maffione, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Pucci, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Sagnotti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Anisotropy of magnetic susceptibility (AMS) represents a valuable proxy able to detect subtle strain effects in very weakly deformed sediments. In compressive tectonic settings, the magnetic lineation is commonly parallel to fold axes, thrust faults, and local bedding strike, while in extensional regimes, it is perpendicular to normal faults and parallel to bedding dip directions. The Altotiberina Fault (ATF) in the northern Apennines (Italy) is a Plio-Quaternary NNW–SSE low-angle normal fault; the sedimentary basin (Tiber basin) at its hanging-wall is infilled with a syn-tectonic, sandy-clayey continental succession. We measured the AMS of apparently undeformed sandy clays sampled at 12 sites within the Tiber basin. The anisotropy parameters suggest that a primary sedimentary fabric has been overprinted by an incipient tectonic fabric. The magnetic lineation is well developed at all sites, and at the sites from the western sector of the basin it is oriented sub-perpendicular to the trend of the ATF, suggesting that it may be related to extensional strain. Conversely, the magnetic lineation of the sites from the eastern sector has a prevailing N–S direction. The occurrence of triaxial to prolate AMS ellipsoids and sub-horizontal magnetic lineations suggests that a maximum horizontal shortening along an E–W direction occurred at these sites. The presence of compressive AMS features at the hanging-wall of the ATF can be explained by the presence of gently N–Strending local folds (hardly visible in the field) formed by either passive accommodation above an undulated fault plane, or rollover mechanism along antithetic faults. The long-lasting debate on the extensional versus compressive Plio-Quaternary tectonics of the Apennines orogenic belt should now be revised taking into account the importance of compressive structures related to local effects. Sat, 31 Mar 2012 22:00:00 GMT http://hdl.handle.net/2122/7907 2012-03-31T22:00:00Z http://hdl.handle.net/2122/7869 Title: Correlation of welded ignimbrites on Pantelleria (Strait of Sicily) using paleomagnetism Authors: Speranza, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Di Chiara, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Rotolo, S. G.; Dipartimento di Scienze della Terra e del Mare (DISTeM), Università di Palermo, Via Archirafi 36, 90123 Palermo, Italy Abstract: Although the oldest volcanic rocks exposed at Pantelleria (Strait of Sicily) are older than 300 ka, most of the island is covered by the 45–50 ka Green Tuff ignimbrite, thought to be related to the Cinque Denti caldera, and younger lavas and scoria cones. Pre-50 ka rocks (predominantly rheomorphic ignimbrites) are exposed at isolated sea cliffs, and their stratigraphy and chronology are not completely resolved. Based on volcanic stratigraphy and K/Ar dating, it has been proposed that the older La Vecchia caldera is related to ignimbrite Q (114 ka), and that ignimbrites F, D, and Z (106, 94, and 79 ka, respectively) were erupted after caldera formation. We report here the paleomagnetic directions obtained from 23 sites in ignimbrite P (133 ka) and four younger ignimbrites, and from an uncorrelated (and loosely dated) welded lithic breccia thought to record a caldera-forming eruption. The paleosecular variation of the geomagnetic field recorded by ignimbrites is used as correlative tool, with an estimated time resolution in the order of 100 years. We find that ignimbrites D and Z correspond, in good agreement with recent Ar/Ar ages constraining the D/Z eruption to 87 ka. The welded lithic breccia correlates with a thinner breccia lying just below ignimbrite P at another locality, implying that collapse of the La Vecchia caldera took place at ~130–160 ka. This caldera was subsequently buried by ignimbrites P, Q, F, and D/Z. Paleomagnetic data also show that the northern caldera margin underwent a ~10° west–northwest (outwards) tilting after emplacement of ignimbrite P, possibly recording magma resurgence in the crust. Wed, 29 Feb 2012 23:00:00 GMT http://hdl.handle.net/2122/7869 2012-02-29T23:00:00Z http://hdl.handle.net/2122/7730 Title: On the age of the Early/Middle Eocene boundary and other related events: cyclostratigraphic refinements from the Pyrenean Otsakar section and the Lutetian GSSP Authors: Payros, A.; Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, Universidad del País Vasco, P.O. Box 644, E-48080 Bilbao, Spain; Dinarès-Turell, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Bernaola, G.; Departamento de Ingeniería Minera y Metalúrgica y Ciencias de los Materiales, Escuela Universitaria de Ingeniería Técnica de Minas y Obras Públicas, University of the Basque Country, Beurko Muinoa s/n, E-48901 Barakaldo, Spain; Orue-Etxebarria, X.; Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, Universidad del País Vasco, P.O. Box 644, E-48080 Bilbao, Spain; Apellaniz, E.; Departamento de Estratigrafía y Paleontología, Facultad de Ciencia y Tecnología, Universidad del País Vasco, P.O. Box 644, E-48080 Bilbao, Spain; Tosquella, J.; Departamento de Geodinámica y Paleontología, Facultas de Ciencias Experimentales, Universidad de Huelva, Campus del Carmen, Avenida Tres de Marzo s/n, E-21071 Huelva, Spain Abstract: An integrated bio-, magneto- and cyclostratigraphic study of the Ypresian/Lutetian (Early/Middle Eocene) transition along the Otsakar section resulted in the identification of the C22n/C21r chron boundary and of the calcareous nannofossil CP12a/b zonal boundary; the latter is the main correlation criterion of the Lutetian Global Stratotype Section and Point (GSSP) recently defined at Gorrondatxe (Basque Country). By counting precession-related mudstone–marl couplets of 21 ka, the time lapse between both events was calculated to be 819 ka. This suggests that the age of the CP12a/b boundary, and hence that of the Early/Middle Eocene boundary, is 47.76 Ma, 250 ka younger than previously thought. This age agrees with, and is supported by, estimates from Gorrondatxe based on the time lapse between the Lutetian GSSP and the C21r/C21n boundary. The duration of Chron C21r is estimated at 1.326 Ma. Given that the base of the Eocene is dated at 55.8 Ma, the duration of the Early Eocene is 8 Ma, 0.8 Ma longer than in current time scales. The Otsakar results further show that the bases of planktonic foraminiferal zones E8 and P10 are younger than the CP12a/b boundary. The first occurrence of Turborotalia frontosa, being approximately 550 ka older that the CP12a/b boundary, is the planktonic foraminiferal event that lies closest to the Early/Middle Eocene boundary. The larger foraminiferal SBZ12/13 boundary is located close to the CP12a/b boundary and correlates with Chron C21r, not with the C22n/C21r boundary. Sat, 30 Apr 2011 22:00:00 GMT http://hdl.handle.net/2122/7730 2011-04-30T22:00:00Z