8 research outputs found
A large West Antarctic Ice Sheet explains early Neogene sea-level amplitude
Early to Middle Miocene sea-level oscillations of approximately 40-60 m estimated from far-field records1-3 are interpreted to reflect the loss of virtually all East Antarctic ice during peak warmth2. This contrasts with ice-sheet model experiments suggesting most terrestrial ice in East Antarctica was retained even during the warmest intervals of the Middle Miocene4,5. Data and model outputs can be reconciled if a large West Antarctic Ice Sheet (WAIS) existed and expanded across most of the outer continental shelf during the Early Miocene, accounting for maximum ice-sheet volumes. Here we provide the earliest geological evidence proving large WAIS expansions occurred during the Early Miocene (~17.72-17.40 Ma). Geochemical and petrographic data show glacimarine sediments recovered at International Ocean Discovery Program (IODP) Site U1521 in the central Ross Sea derive from West Antarctica, requiring the presence of a WAIS covering most of the Ross Sea continental shelf. Seismic, lithological and palynological data reveal the intermittent proximity of grounded ice to Site U1521. The erosion rate calculated from this sediment package greatly exceeds the long-term mean, implying rapid erosion of West Antarctica. This interval therefore captures a key step in the genesis of a marine-based WAIS and a tipping point in Antarctic ice-sheet evolution
A lithostratigraphic reappraisal of a Permian-Triassic fluvial succession at Allan Hills (Antarctica) and implications for the terrestrial end-Permian extinction event
Between Permian to Triassic, the Earth experienced climatic and biotic crises, included the
greatest mass extinction at the Permian-Triassic boundary. These climatic and biological changes are
reflected in both marine and terrestrial depositional systems. Over this time span, the Gondwana
supercontinent hosted numerous large basins that may preserve the paleoenvironment response to
global changes in the sedimentary record. This study provides a lithostratigraphic reappraisal of the
latest Paleozoic-Mesozoic alluvial Beacon Supergroup at Allan Hills (Convoy Range), which is one of
the most complete sedimentary sequences in Antarctica. Fieldwork stratigraphic-lithological
observation, facies analysis, and petrographic characterization of sedimentary rocks allow the
identification of six depositional units. The investigations point out for a conformable relationship
between depositional and lithostratigraphic units, characterized by changes in the fluvial style. The
reconnaissance of a “transitional interval” showing intermediate features between the Permian Weller
Coal Measures and the Triassic Feather Conglomerate strengthen the conformable nature of the sequence across the Permian-Triassic boundary in this region. The lithological features of such
interval strongly resemble those observed in the coeval deeply studied Eastern Australia successions
crossing the Permian-Triassic boundary as well as the end-Permian extinction. More precisely, the
uppermost coal occurrence, just above a glossopterid macroflora-bearing carbonaceous mudstone
within the “transitional interval”, marks the disappearance of coal-peat forming Permian vegetation
which corresponds with the terrestrial end-Permian extinction, thus representing one of the few end-
Permian extinction records in Antarctica
Attivita' di donazione, prelievo e trapianto di organi nella regione Toscana. Report 2003
On the cover: CRT report 2003Consiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7 , Rome / CNR - Consiglio Nazionale delle RichercheSIGLEITItal
A large West Antarctic Ice Sheet explains early Neogene sea-level amplitude
Early to Middle Miocene sea-level oscillations of approximately 40–60 m estimated from far-field records1,2,3 are interpreted to reflect the loss of virtually all East Antarctic ice during peak warmth2. This contrasts with ice-sheet model experiments suggesting most terrestrial ice in East Antarctica was retained even during the warmest intervals of the Middle Miocene4,5. Data and model outputs can be reconciled if a large West Antarctic Ice Sheet (WAIS) existed and expanded across most of the outer continental shelf during the Early Miocene, accounting for maximum ice-sheet volumes. Here we provide the earliest geological evidence proving large WAIS expansions occurred during the Early Miocene (~17.72–17.40 Ma). Geochemical and petrographic data show glacimarine sediments recovered at International Ocean Discovery Program (IODP) Site U1521 in the central Ross Sea derive from West Antarctica, requiring the presence of a WAIS covering most of the Ross Sea continental shelf. Seismic, lithological and palynological data reveal the intermittent proximity of grounded ice to Site U1521. The erosion rate calculated from this sediment package greatly exceeds the long-term mean, implying rapid erosion of West Antarctica. This interval therefore captures a key step in the genesis of a marine-based WAIS and a tipping point in Antarctic ice-sheet evolutio
A large West Antarctic ice sheet explains early Neogene sea-level amplitude
Early to Middle Miocene sea-level oscillations of approximately 40–60 m estimated from far-field records1–3 are interpreted to reflect the loss of virtually all East Antarctic ice during peak warmth2. This contrasts with ice-sheet model experiments suggesting most terrestrial ice in East Antarctica was retained even during the warmest intervals of the Middle Miocene4,5. Data and model outputs can be reconciled if a large West Antarctic Ice Sheet (WAIS) existed and expanded across most of the outer continental shelf during the Early Miocene, accounting for maximum ice-sheet volumes. Here we provide the earliest geological evidence proving large WAIS expansions occurred during the Early Miocene (~17.72–17.40 Ma). Geochemical and petrographic data show glacimarine sediments recovered at International Ocean Discovery Program (IODP) Site U1521 in the central Ross Sea derive from West Antarctica, requiring the presence of a WAIS covering most of the Ross Sea continental shelf. Seismic, lithological and palynological data reveal the intermittent proximity of grounded ice to Site U1521. The erosion rate calculated from this sediment package greatly exceeds the long-term mean, implying rapid erosion of West Antarctica. This interval therefore captures a key step in the genesis of a marine-based WAIS and a tipping point in Antarctic ice-sheet evolution