Search results for "Geophysics"

Jurassic evolution of the Arabian carbonate platform edge in the central Oman Mountains

2005

International audience; The Jurassic Sahtan Group exposed in northern Oman was deposited in shallow marine environments at the edge of the Arabian Platform facing the Neo-Tethys (Hamrat Duru Basin). The upper Sahtan Group is made up of a mixed siliciclastic-carbonate unit overlain by pure carbonate deposits, assigned to a Bathonian and Early Callovian age on the basis of brachiopods and foraminifers. These carbonate depositional systems were composed of outer oolitic shoals that underwent subaerial exposure, and a deeper, somewhat restricted, gently dipping shelf interior. Oolitic material was shed off the platform edge into the deep-sea depositional complex of the Guweyza Formation. The Sa…

Subduction‐Induced Back‐Arc Extension Versus Far‐Field Stretching: Contrasting Modes for Continental Marginal Break‐Up

2021

Peri-Gondwanan Ordovician arc magmatism in southeastern Ireland and the Isle of Man: Constraints on the timing of Caledonian deformation in Ganderia

2018

The timing of and tectonic controls on Ordovician magmatism and deformation within accreted terranes are key elements in reconstructing the generation of the Caledonian-Appalachian orogen. This pap ...

Sulfur isotope's signal of nanopyrites enclosed in 2.7 Ga stromatolitic organic remains reveal microbial sulfate reduction.

2018

18 pages; International audience; Microbial sulfate reduction (MSR) is thought to have operated very early on Earth and is often invoked to explain the occurrence of sedimentary sulfides in the rock record. Sedimentary sulfides can also form from sulfides produced abiotically during late diagenesis or metamorphism. As both biotic and abiotic processes contribute to the bulk of sedimentary sulfides, tracing back the original microbial signature from the earliest Earth record is challenging. We present in situ sulfur isotope data from nanopyrites occurring in carbonaceous remains lining the domical shape of stromatolite knobs of the 2.7-Gyr-old Tumbiana Formation (Western Australia). The anal…

Millennial-scale phase relationships between ice-core and Mediterranean marine records: insights from high-precision 40Ar/39Ar dating of the Green Tu…

2013

International audience; With the advent of annually-resolved polar ice records extending back to 70 ka, marine and continental paleoclimate studies have now matured into a discipline where high-quality age control is essential for putting on an equal pace layer-counted timescale models and Late Quaternary sedimentary records. High-resolution U-Th dating of speleothem records and 40Ar/39Ar dating of globally recorded geomagnetic excursions have recently improved the time calibration of Quaternary archives, reflecting the cross-disciplinary effort made to synchronize the geologic record at the millennial scale. Yet, tie-points with such an absolute age control remain scarce for paleoclimatic …

Planning Punic cities: Geophysical prospection and the built environment at Motya, Sicily

2020

The urban plan of ancient Motya on the Isola di San Pantaleo on the west coast of Sicily and its relationship to developments in Phoenician and Punic societies have been investigated since the early 1960s. Data from geophysical surveys in the north-eastern quadrant of Motya show the regular organisation of urban insulae framed by two broad roads. These results, combined with data from previous nearby excavations, improve the modelling of Motya's layout, and contribute to the wider discussion of Phoenician/Punic and broader Mediterranean urban traditions between the sixth and fourth centuries BC.

The production cycle of lime-based plasters in the Late Roman settlement of Scauri, on the island of Pantelleria, Italy

2018

This paper deals with the archaeometric study of lime-based plasters found in the archaeological settlement of Scauri, located in the homonymous bay in the south-western part of Pantelleria Island. Since 1999, archaeological surveys have led to the recovery of the huge remains of a Late Roman settlement dating back to the fourth-fifth century AD. It is well known that the island of Pantelleria is entirely composed of volcanic rocks. Accordingly, the production of quicklime required calcareous rocks to be imported. Also, the selection criteria of the sandy aggregate are relevant and of interest to this study, to evaluate the achieved technological level. Within this context, a mineralogical …

Detección de un nuevo campamento romano en las inmediaciones de Mérida mediante tecnología LiDAR

2018

En las últimas décadas, el crecimiento exponencial de trabajos interesados en la Arqueología Militar de época romana ha permitido cubrir un importante hueco de la historiografía arqueológica peninsular, destacándose el análisis del proceso de conquista e implantación del poder romano entre los ss. II-I a. n. e. Esta línea de trabajo se ha centrado, especialmente, en el estudio de los campamentos legionarios (castra), entre cuyos problemas destaca el poco conocimiento disponible sobre su relación con eventos históricos concretos. Así pues, en esta breve noticia abordamos la contextualización de una serie de estructuras localizadas mediante LiDAR en la rivera de Lácara, afluente del río Guadi…

Ranking of tree-ring based temperature reconstructions of the past millennium

2016

German Science Foundation [161/9-1]; National Natural Science Foundation of China [41325008]; [RNF 15-14-30011]

2017

Ranking among the largest volcanic eruptions of the Common Era (CE), the ‘Millennium Eruption’ of Changbaishan produced a widely-dispersed tephra layer (known as the B-Tm ash), which represents an important tie point for palaeoenvironmental studies in East Asia. Hitherto, there has been no consensus on its age, with estimates spanning at least the tenth century CE. Here, we identify the cosmogenic radiocarbon signal of 775 CE in a subfossil larch engulfed and killed by pyroclastic currents emplaced during the initial rhyolitic phase of the explosive eruption. Combined with glaciochemical evidence from Greenland, this enables us to date the eruption to late 946 CE. This secure date rules out…