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Bracciali, L.
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Bracciali, L.
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- PublicationRestrictedThe upper lithostratigraphic unit of ANDRILL AND-2A core (Southern McMurdo Sound, Antarctica): Local Pleistocene volcanic sources, paleoenvironmental implications and subsidence in the southern Victoria Land Basin(2009-11)
; ; ; ; ; ; ;Del Carlo, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Panter, K. S.; Department of Geology, Bowling Green State University, Bowling Green, OH, USA ;Bassett, K.; Department of Geological Science, University of Canterbury, Christchurch, New Zealand ;Bracciali, L.; Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy ;Di Vincenzo, G.; Istituto di Geoscienze e Georisorse, CNR, Pisa, Italy ;Rocchi, S.; Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy; ; ; ; ; We report results from the study of the uppermost 37 m of the Southern McMurdo Sound (SMS) AND-2A drill core, corresponding to the lithostratigraphic unit 1 (LSU 1), the most volcanogenic unit within the core. We present data on the age, composition, volcanological and depositional features of the volcanic sedimentary and tephra deposits of LSU 1 and discuss their source, mechanisms of emplacement and environment of deposition. Sedimentary features and compositional data indicate shallow water sedimentation for the whole of LSU 1. Most of LSU 1 deposits are a mixture of near primary volcanic material with minor exotic clasts derived from the Paleozoic crystalline basement rocks. Among volcanic materials, glassy particles are the most abundant. They were produced by mildly explosive basaltic eruptions occurring in subaerial and subaqueous environments. The Dailey Islands group, 13 km south-southwest of the SMS drill-site, has been identified as a possible source for the volcanics on the basis of similarity in composition and age. 40Ar–39Ar laser step-heating analyses on a lava sample from Juergens Island yields an age of 775 ± 22 ka. Yet because of the minimal reworking features of vitriclasts, preservation of fragile structures in volcaniclastic sediments and evidence for volcanic seamounts to the north of the Dailey Islands, it is likely that some of the material originated also from vents close to the drill-site. Evidence for local volcanic sources and for deposition of sediments in a shallow marine environment provides indications about the local paleogeography and implications for the subsidence history of the southern Victoria Land Basin from Pleistocene to Recent.144 31 - PublicationRestrictedPetrologic and Geochemical Composition of of the AND-2A Core, ANDRILL Southern McMurdo Sound Project, Antarctica(2009-12)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Panter, K. S.; Dept. of Geology, Bowling Green State University, Bowling Green, USA ;Talarico, F. M.; 2Dip. di Scienze della Terra, Università di Siena, Siena, Italy ;Bassett, K.; Dept. of Geological Science, University of Canterbury, Christchurch, New Zealand ;Del Carlo, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Field, B.; GNS Science, Lower Hutt, New Zealand ;Frank, T.; Dept. of Geosciences, University of Nebraska-Lincoln, Lincoln, USA ;Hoffman, S.; Dept. of Sedimentology & Environ., Geology, Geoscience Center Göttingen (GZG), Göttingen, Germany ;Kuhn, G.; Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany ;Reichelt, L.; Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany ;Sandroni, S.; Dipt. di Scienze della Terra, Università di Siena, Siena, Italy ;Taviani, M.; ISMAR-CNR, Bologna − Italy ;Bracciali, L.; Dipt. di Scienze della Terra, Università di Pisa, Pisa, Italy ;Cornamusini, G.; Dipt. di Scienze della Terra, Università di Siena, Siena, Italy; Centro di Geotecnologie, Università di Siena, Arezzo, Italy ;von Eynatten, H.; Dept. of Sedimentology & Environ., Geology, Geoscience Center Göttingen (GZG), Göttingen, Germany ;Rocchi, S.; Dipt. di Scienze della Terra, Università di Pisa, Pisa, Italy; ; ; ; ; ; ; ; ; ; ; ; ; ; The compositional record of the AND-2A drillcore is examined using petrological, sedimentological, volcanological and geochemical analysis of clasts, sediments and pore waters. Preliminary investigations of basement clasts (granitoids and metasediments) indicate both local and distal sources corresponding to variable ice-volume and ice-flow directions. Low abundance of sedimentary clasts (e.g., arkose, litharenite) suggests reduced contributions from sedimentary covers while intraclasts (e.g., diamictite, conglomerate) attest to intrabasinal reworking. Volcanic material includes pyroclasts (e.g., pumice, scoria), sediments and lava. Primary and reworked tephra layers occur within the Early Miocene interval (1093 to 640 metres below sea floor). The compositions of volcanic clasts reveal a diversity of alkaline types derived from the McMurdo Volcanic Group. Finer-grained sediments (e.g., sandstone, siltstone) show increases in biogenic silica and volcanic glass from 230 to 780 mbsf and higher proportions of terrigenous material ca. 350 to 750 mbsf and below 970 mbsf. Basement clast assemblages suggest a dominant provenance from the Skelton Glacier -Darwin Glacier area and from the Ferrar Glacier -Koettlitz Glacier area. Provenance of sand grains is consistent with clast sources. Thirteen Geochemical Units are established based on compositional trends derived from continuous XRF scanning. High values of Fe and Ti indicate terrigenous and volcanic sources, whereas high Ca values signify either biogenic or diagenic sources. Highly alkaline and saline pore waters were produced by chemical exchange with glass at moderately elevated temperatures.229 18 - PublicationOpen AccessPetrologic and Geochemical Composition of the AND-2A Core, ANDRILL Southern McMurdo Sound Project, Antartica(2009)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Panter, K. S.; Dept. of Geology, Bowling Green State University, Bowling Green, OH, 43403 – USA ;Talarico, F. M.; Dipt. di Scienze della Terra, Università di Siena, Siena – Italy ;Bassett, K.; Dept. of Geological Science, University of Canterbury, Private Bag 4800, Christchurch - New Zealand ;Del Carlo, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Field, B.; GNS Science, 1 Fairway Ave, Lower Hutt − New Zealand ;Frank, T.; Dept. of Geosciences, University of Nebraska-Lincoln, Lincoln, NE 68588 − USA ;Hoffman, S.; Dept. of Sedimentology & Environ., Geology, Geoscience Center Göttingen (GZG), Goldschmidtstr. 3, 37077 Göttingen − Germany ;Kuhn, G.; Alfred Wegener Institute for Polar and Marine Research, 27568 Bremerhaven – Germany ;Reichelt, L.; Dept. of Sedimentology & Environ., Geology, Geoscience Center Göttingen (GZG), Goldschmidtstr. 3, 37077 Göttingen − Germany ;Sandroni, S.; Dipt. di Scienze della Terra, Università di Siena, Siena – Italy ;Taviani, M.; ISMAR-CNR, Bologna −Italy ;Bracciali, L.; Dipt. di Scienze della Terra, Università di Pisa, Pisa −Italy ;Cornamusini, G.; Dipt. di Scienze della Terra, Università di Siena, Siena – Italy; Centro di Geotecnologie, Università di Siena, San Giovanni Val d’Arno, Arezzo – Italy ;von Eynatten, H.; Dept. of Sedimentology & Environ., Geology, Geoscience Center Göttingen (GZG), Goldschmidtstr. 3, 37077 Göttingen − Germany ;Rocchi, R.; Dipt. di Scienze della Terra, Università di Pisa, Pisa , Italy; ; ; ; ; ; ; ; ; ; ; ; ; ; The compositional record of the AND-2A drillcore is examined using petrological, sedimentological, volcanological and geochemical analysis of clasts, sediments and pore waters. Preliminary investigations of basement clasts (granitoids and metasediments) indicate both local and distal sources corresponding to variable ice-volume and ice-flow directions. Low abundance of sedimentary clasts (e.g., arkose, litharenite) suggests reduced contributions from sedimentary covers while intraclasts (e.g., diamictite, conglomerate) attest to intrabasinal reworking. Volcanic material includes pyroclasts (e.g., pumice, scoria), sediments and lava. Primary and reworked tephra layers occur within the Early Miocene interval (1093 to 640 metres below sea floor). The compositions of volcanic clasts reveal a diversity of alkaline types derived from the McMurdo Volcanic Group. Finer-grained sediments (e.g., sandstone, siltstone) show increases in biogenic silica and volcanic glass from 230 to 780 mbsf and higher proportions of terrigenous material ca. 350 to 750 mbsf and below 970 mbsf. Basement clast assemblages suggest a dominant provenance from the Skelton Glacier - Darwin Glacier area and from the Ferrar Glacier - Koettlitz Glacier area. Provenance of sand grains is consistent with clast sources. Thirteen Geochemical Units are established based on compositional trends derived from continuous XRF scanning. High values of Fe and Ti indicate terrigenous and volcanic sources, whereas high Ca values signify either biogenic or diagenic sources. Highly alkaline and saline pore waters were produced by chemical exchange with glass at moderately elevated temperatures.262 594 - PublicationRestricted40Ar–39Ar dating of volcanogenic products from the AND-2A core (ANDRILL Southern McMurdo Sound Project, Antarctica): correlations with the Erebus Volcanic Province and implications for the age model of the core(2010-05)
; ; ; ; ; ;Di Vincenzo, G.; Istituto di Geoscienze e Georisorse, CNR, Pisa, Italy ;Bracciali, L.; Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy ;Del Carlo, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Panter, K.; Department of Geology, Bowling Green State University, Bowling Green, OH, USA ;Rocchi, S.; Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy; ; ; ; The AND-2A drillcore (Antarctic Drilling Program—ANDRILL) was successfully completed in late 2007 on the Antarctic continental margin (Southern McMurdo Sound, Ross Sea) with the aim of tracking ice proximal to shallow marine environmental fluctuations and to document the 20-Ma evolution of the Erebus Volcanic Province. Lava clasts and tephra layers from the AND-2A drillcore were investigated from a petrographic and stratigraphic point of view and analyzed by the 40Ar–39Ar laser technique in order to constrain the age model of the core and to gain information on the style and nature of sediment deposition in the Victoria Land Basin since Early Miocene. Ten out of 17 samples yielded statistically robust 40Ar–39Ar ages, indicating that the AND-2A drillcore recovered ≤230 m of Middle Miocene (∼128–358 m below sea floor, ∼11.5–16.0 Ma) and >780 m of Early Miocene (∼358–1093 m below sea floor, ∼16.0–20.1 Ma). Results also highlight a nearly continuous stratigraphic record from at least 358 m below sea floor down hole, characterized by a mean sedimentation rate of ∼19 cm/ka, possible oscillations of no more than a few hundreds of ka and a break within ∼17.5–18.1 Ma. Comparison with available data from volcanic deposits on land, suggests that volcanic rocks within the AND-2A core were supplied from the south, possibly with source areas closer to the drill site for the upper core levels, and from 358 m below sea floor down hole, with the “proto-Mount Morning” as the main source.231 19 - PublicationEmbargoCoupled U–Pb and 40Ar/39Ar chronology of late‐stage intrusions at Elba Island (Italy) supports late Miocene long‐lived magma reservoirs in the Tyrrhenian upper crust(2024-02-07)
; ; ; ; ; ; ; ; ; ; ; The late Miocene Monte Capanne and Porto Azzurro plutons are investigated by means of coupled U-Pb zircon and 40Ar/39Ar white mica dating to test the occurrence of long-lived magmatic systems in the upper crust. Zircon crystallized for > 1 Myr in both plutonic systems, with supersolidus conditions overlapping for ~220 kyr indicating previously unrecognized co-existence of the two reservoirs. The development of the Porto Azzurro high T-aureole is post-dated by continuous igneous zircon crystallization until ~ 6.0 Ma. By linking crystallization to post-emplacement cooling of late-stage pulses in both western and eastern Elba we constrain long-lived sizeable reservoirs (possibly the same reservoir) in the Tyrrhenian upper crust between ~8 and 6 Ma.46 16