Search results for "Sequence stratigraphy"

Eustasy and sea water Sr composition: application to high-resolution Sr-isotope stratigraphy of Miocene shallow-water carbonates

2007

Oceanic 87 Sr/ 86 Sr-isotope ratios are strongly influenced by rates of silicate weathering and therefore linked not only to glaciation but also to sea-level change. The present study combines analysis of sequence stratigraphy and basin architecture with Sr-isotope stratigraphy in Miocene shallow-water sediments in southern Portugal and Crete (Greece). The common method is to use smoothed global sea water Sr-isotope reference curves but here a different approach is chosen. Instead, measured Sr-isotope curves are correlated with unsmoothed reference curves by identification of similar fluctuations in the order of several 100 kyr. Transgressive intervals are characterized by increasing Sr-iso…

Black shale deposition during Toarcian super-greenhouse driven by sea level

2013

Abstract. One of the most elusive aspects of the Toarcian oceanic anoxic event (T-OAE) is the paradox between carbon isotopes that indicate intense global primary productivity and organic carbon burial at a global scale, and the delayed expression of anoxia in Europe. During the earliest Toarcian, no black shales were deposited in the European epicontinental seaways, and most organic carbon enrichment of the sediments postdated the end of the overarching positive trend in the carbon isotopes that characterises the T-OAE. In the present study, we have attempted to establish a sequence stratigraphic framework for Early Toarcian deposits recovered from a core drilled in the Paris Basin using a…

Sequence stratigraphy and carbon isotope stratigraphy of an Aptian mixed carbonate-siliciclastic platform to basin transition (Galve sub-basin, NE Sp…

2010

The Late Ordovician glacial sedimentary system of the North Gondwana platform.

2009

International audience; The Late Ordovician (Hirnantian) glaciation is examined through the North Gondwana record. This domain extended from southern high palaeo-latitudes (southeastern Mauritania, Niger) to northern lower palaeo-latitudes (Morocco, Turkey) and covered a more than 4000 km-wide section perpendicular to ice-flow lines. A major mid-Hirnantian deglaciation event subdividing the Hirnantian glaciation in two first-order cycles is recognised. As best illustrated by the glacial record in western Libya, each cycle comprises 2-3 glacial phases separated by ice-front retreats several hundreds kilometres to the south. From ice-proximal to ice-distal regions, the number of glacial surfa…

Chronostratigraphy and geochronology: A proposed realignment.

2013

We propose a realignment of the terms geochronology and chronostratigraphy that brings them broadly into line with current use, while simultaneously resolving the debate over whether the Geological Time Scale should have a “single” or “dual” hierarchy of units: Both parallel sets of units are retained, although there remains the option to adopt either a single (i.e., geochronological) or a dual hierarchy in particular studies, as considered appropriate. Thus, geochronology expresses the timing or age of events (depositional, diagenetic, biotic, climatic, tectonic, magmatic) in Earth’s history (e.g., Hirnantian glaciation, Famennian-Frasnian mass extinction). Geochronology can also qualify r…

Refitting lithic laminar fragments to assess Palaeolithic sequences: The case of Cova de les Cendres (Teulada-Moraira, Alicante, Spain)

2020

Abstract The integrity of the different levels that form a sequence and the formation processes of the archaeological deposit must be assessed as a previous step to the construction of behavioural, cultural and evolutionary interpretations. This is especially relevant when dealing with long sequences and cultural evolution constructed on them, as is the case in the research on Upper Palaeolithic. Lithic taphonomy provides insight into these issues and refitting is one of its powerful tools. This approach has been applied to the Aurignacian, Gravettian and Solutrean levels of Cova de les Cendres (Teulada-Moraira, Alicante, Spain), where fracture refits of laminar fragments –including blades,…

The owl that never left! Taphonomy of Earlier Stone Age small mammal assemblages from Wonderwerk Cave (South Africa)

2022

Wonderwerk Cave, in South Africa, is an exceptional site that has yielded a large collection of small mammal fossils in a stratigraphic sequence reaching back ca. 2 million years. Taphonomic studies undertaken to date, show that Tytonidae (likely Tyto alba) was the dominant predator during the Earlier Stone Age. They produced masses of pellets that formed a dense carpet-like surface that covered the cave floor at intervals throughout the sequence. This paper compares the taphonomic signatures of five different Earlier Stone Age small mammal assemblages from Wonderwerk Cave, including assemblages not studied before, as well as a modern pellet assemblage collected from inside the cave. These …

Nouvelles données biostratigraphiques sur les dépots cénomanoturoniens du Nord-Est du fosse de ia Bénoué (Nigéria)

1993

Abstract The Upper Cretaceous deposits of the Upper Benue (North-East Nigeria) record regional and local events (sea-level changes, biological successions and tectonic movements) which throw light on the Upper Cenomanian transgression. Evidence of discontinuities and sedimentary assemblages well dated by micropalaeontological data, allows the sedimentary sequence to be interpreted in the context of sequence stratigraphy. The discovery of new ammonite faunas has enabled a more precise definition of the local biostratigraphy and a correlation of this with the standard zonal scheme. In the near future, when they are better known, the ammonite successions recognized in the Upper Benue could ena…

Lanthanides Revealing Anthropogenic Impact within a Stratigraphic Sequence

2014

Difficulties to differentiate between anthropogenic and natural processes in the formation of archaeological deposits are crucial for a correct interpretation not only of the actions involved in the development of archaeological sites, but also of their occupation-abandonment dynamics and the understanding of their spatial behaviors and relationship with the environment. We have carried out lanthanides (rare earth elements “REE”) analysis to distinguish anthropogenic from natural stratigraphic units in sediments using the advantage of the high sensibility, precision, and accuracy of ICP-MS measurements. In the Neolithic site of Mas d’Is (Alacant, Spain), we have applied REE analysis in a hu…

Rectilinear evolution in arvicoline rodents and numerical dating of Iberian Early Pleistocene sites

2014

Abstract Lozano-Fernandez et al. (2013a) have recently published a method intended for numerical dating of Early Pleistocene sites, which is based on the assumption of uniform, constant rate increase through time of mean lower molar tooth length of water voles ( Mimomys savini ) in a number of levels sampled in the stratigraphic sequence of Atapuerca TD site. They suggest that the regression equation obtained in this local section for site chronology on tooth size could be useful for estimating the numerical age of other localities from southwestern Europe. However, in our opinion this biostratigraphic approach has severe conceptual and methodological problems, which discourage its use as a…