Turbidite Megabeds in an Oceanic Rift Valley Recording Jokulhlaups of Late Pleistocene Glacial Lakes of the Western United States

Escanaba Trough is the southernmost segment of the Gorda Ridge and is filled by sandy turbidites locally exceeding 500 m in thickness. New results from Ocean Drilling Program (ODP) Sites 1037 and 1038 that include accelerator mass spectrometry (AMS) C-14 dates and revised petrographic evaluation of the sediment provenance, combined with high-resolution seismic-reflection profiles, provide a lithostratigraphic framework for the turbidite deposits. Three fining-upward units of sandy turbidites from the upper 365 m at ODP Site 1037 can be correlated with sediment recovered at ODP Site 1038 and Deep Sea Drilling Program (DSDP) Site 35. Six AMS C-14 ages in the upper 317 m of the sequence at Site 1037 indicate that average deposition rates exceeded 10 m/k.yr. between 32 and 11 ka, with nearly instantaneous deposition of one similar to 60-m interval of sand. Petrography of the sand beds is consistent with a Columbia River source for the entire sedimentary sequence in Escanaba Trough. High-resolution acoustic stratigraphy shows that the turbidites in the upper 60 m at Site 1037 provide a characteristic sequence of key reflectors that occurs across the floor of the entire Escanaba Trough. Recent mapping of turbidite systems in the northeast Pacific Ocean suggests that the turbidity currents reached the Escanaba Trough along an 1100-km-long pathway from the Columbia River to the west flank of the Gorda Ridge. The age of the upper fining-upward unit of sandy turbidites appears to correspond to the latest Wisconsinan outburst of glacial Lake Missoula. Many of the outbursts, or jokulhlaups, from the glacial lakes probably continued flowing as hyperpycnally generated turbidity currents on entering the sea at the mouth of the Columbia River

Ciclo di Seminari- GRUPPO ITALIANO DI RIFERIMENTO IODP

A) Il progetto IODP - Angelo Camerlenghi (ICREA - Universita\u2019 di Barcelona) B) Il superplume e la super-greenhouse del Cretacico medio: le perforazioni ODP raccontano i climi estremi del passato - Elisabetta Erba (Universita\u2019 di Milano) C) La prima perforazione profonda nell\u2019Oceano Artico: implicazioni per la storia del clima del Cenozoico - Domenico Rio (Universita\u2019 di Padova) D) Dinamica delle zone di subduzione: sismogenesi e limiti di placca nell'esplorazione IODP - Paola Vannucchi (Universita\u2019 di Firenze) C.L. Scienze Ambientali Aula Magna (via S.Alberto, 163 Ravenna) Gioved\uec 2 febbraio 2006 Ore 10,30 \u2013 13,00 / 14,30- 17,0

Sand composition changes across key boundaries of siliciclastic and hybrid depositional sequences

Sand composition of arenite successions is sensitive to a suite of factors operating between initial grain production and final diagenesis on a variety of spatial and temporal scales. Seven allogenic factors, the relative importance of which relies upon the complex interaction between tectonics, eustasy and climate, play a decisive role in dictating petrofacies distribution within siliciclastic to hybrid depositional sequences. These factors include: i) tectonic exhumation, ii) physical and chemical rock breakdown, iii) change in sediment flux, iv) change in source/basin physiography, v) shelf colonization by organisms, vi) generation of chemical grains, and vii) volcanism. Autogenic processes may locally have a considerable influence on the type and amount of sediment supplied to the basin, thus interfering with the external control. Based upon literature data, a conceptual framework of expected compositional changes across the key surfaces for sequence-stratigraphic interpretation is outlined. Two case histories, from the Miocene shelf-to-turbidite deposits of the northern Apennines and the Quaternary alluvial-to-nearshore succession of the Adriatic coast, respectively, are used as references to illustrate how arenite petrofacies changes can be framed into a sequence-stratigraphic scheme on multiple timescales

Thermal history and exhumation of the Northern Apennines (Italy): evidence from combined apatite fission track and vitrinite reflectance data from foreland basin sediments

Apatite fission track ages of 20 samples collected from turbidite successions deposited in foreland basins adjacent to the Northern Apennines range between similar to3 and similar to 10 Ma. The youngest fission track ages are concentrated in a NW-SE elongated belt, which approximately runs through the centre of the study area, while gradually increasing ages are distributed towards the south-western and north-eastern borders. Integration of apatite fission track data and published vitrinite reflectance values indicate this region of the Apennines experienced continuous but variable exhumation starting from similar to 14 Ma. The extent of exhumation and uplift range between 5 and 6 km at the south-western and north-eastern borders of the study area, and similar to7 km in the central part. Exhumation was driven mainly by erosion, with minor faulting in response to structural readjustment related to differential exhumation. Regional exhumation and erosion are interpreted as the result of isostatic rebound following crustal thickening in the lower part of the orogen

Palaeogeography of the Upper Cretaceous-Eocene Carbonate Turbidites of the Northern Apennines from Provenance Studies

The Upper Cretaceous Helminthoid Flysch (HF) of the Northern Apennines consists of thick and regionally widespread deep-water carbonate turbidite successions, deposited during the initial stages of Alpine collision. The HF spans the time from Turonian to Early Eocene and is mainly composed of intrabasinal carbonate ooze mixed with clay; siliciclastic terrigenous beds are also present, but they are a volumetrically minor component of the successions. Petrographic and sedimentological signatures indicate that the HF was deposited in distinct basins located below the carbonate compensation depth. Bulk composition and heavy minerals of terrigenous beds indicate provenance from different crustal levels of the European and Adria plates. The petrographic and palaeobathymetric characteristics of these turbidites indicate the coexistence of an active-margin tectonic setting, a palaeogeographical position suitable for carbonate ooze production and storage, and limited supply of terrigenous detritus into the basin. Palaeotectonic reconstructions and stratigraphic data suggest that Adria represented a vast repository of penecon-temporaneous carbonate mud; the presumably intense seismic activity related to the pre-collisional Alpine orogeny promoted large-scale failures of shelf and/or slope biogenic muddy sediments, resulting in the deposition of a large volume of carbonate turbidites. Only occasionally, turbidity currents probably linked to exceptional fluvial floods generated pure terrigenous beds with different petrographic signatures for each HF succession

Petrostratigraphic evolution of the Thrace Basin (Bulgaria, Greece, Turkey) within the context of Eocene-Oligocene post-collisional evolution of the Vardar-İzmir-Ankara suture zone

Eocene-Oligocene paleogeographic/paleotectonic reconstructions of the Rhodopian - northern Aegean - western Black Sea region largely ignore the Thrace Basin, a large sedimentary basin up to 9 km thick that has been long interpreted as a forearc basin developed in a context of northward subduction. Recent structural, stratigraphic, petrologic, and sedimentologic data challenge this notion and may instead be interpreted within a context of upper-plate extension during the complex transition between the collisional tectonic regime related to the closure of Vardar-Izmir-Ankara oceanic realm and the extensional regime characterizing the Oligocene-Neogene evolution of the Aegean and peri-Aegean regions. The detritus filling the Thrace Basin was derived from two main sediment source areas: (i) the mostly metamorphic terrains of the Rhodopes to the west and (ii) the Vardar-Izmir-Ankara and Biga (intra-Pontide?) subduction-accretion prisms to the southwest. During most of the Eocene-Oligocene, the entire basin was characterized by a complex physiography, as shown by commercial seismic lines in the subsurface and abrupt lateral facies change at the surface. Such physiography was controlled by a series of basement highs trending from WNW-ESE (in the eastern and northern portions of the basin) to WSW-ENE (in the western and southern portions of the basin) which influenced sediment dispersal and the areal distribution of paleoenvironments