Search results for " depositional environment"
showing 10 items of 129 documents
Rereading a tree-ring database to illustrate depositional histories of subfossil trees
2017
Late Quaternary tree-ring chronologies have been constructed using data collected from subfossil trees preserved under favourable conditions in lake sediments and peat deposits. Tree-ring widths and densities are commonly used for reconstructions of past climate variability. An alternative way of using these data is to explore the replication curves of these chronologies. Here, we make use of previously collected data that is currently available from tree-ring databases to demonstrate the depositional histories of pine trees once accumulated into the sediment in lake (i.e., riparian trees) and peatland sites. Divergent courses of depositional histories were obtained for different sedimentar…
Detrital-zircon geochronology and provenance of the El Oro Metamorphic Complex, Ecuador: Geodynamic implications for the evolution of the western Gon…
2019
Abstract The El Oro Metamorphic Complex (EOMC) in SW Ecuador has been the subject of debate for several decades. While previous studies have focused on the metamorphic and deformation history of the complex to determine its geodynamic evolution, the pre-metamorphic history and its association to units in the north-central Andes remains poorly understood. Here we present a U-Pb detrital zircon provenance study to provide insights into the depositional history and the geodynamic setting of the EOMC. Our results imply that the southern portion of the EOMC (the Tahuin division) is composed of an older Palaeozoic (pre-Famatinian) sequence in the south (El Tigre unit; c. 525-510 Ma), and younger …
Depositional environments and iron ooid formation in condensed sections (Callovian Oxfordian, South-eastern part of the Paris basin, France)
2005
Carbonate platforms across Western Europe were superseded at the Middle–Upper Jurassic (Callovian–Oxfordian) boundary either by alternating marl–limestone and widespread marl deposits or by condensed sections containing iron ooids. The characteristics of marine condensed sections in the south-eastern part of the Paris Basin (France) and their distribution pattern are examined here, and a model of iron ooid formation is developed. Iron ooids are found from the shoreface to the offshore zone. They are most abundant in the median-to-distal offshore transition zone, where they originally formed. They also occur commonly, albeit often as reworked grains, in the proximal offshore zone, to which t…
Intact seismic-scale platforms and ramps in the Lower to Middle Jurassic of Morocco: implications for stratal anatomy and lithofacies partitioning.
2017
9 pages; International audience; The Jurassic carbonate platforms of the central High Atlas in Morocco are well known for several high-quality outcrops. In the central High Atlas, there are two complementary locations that offer critical lessons for our understanding of Jurassic carbonate system evolution in extensional basins: a Lower Jurassic high-relief, carbonate platform with steep slopes that developed on the footwall of a rotating fault block in an active half-graben (Djebel Bou Dahar [DBD]) and an upper Lower to Middle Jurassic low-angle prograding carbonate ramp rich in ooids (Amellago ramp [AR]). The DBD and AR outcrops provide superbly exposed, structurally intact, and fully acce…
Biostratigraphy, Chronostratigraphy and Paleonvironmental Reconstruction of the Palermo Historical Centre Quaternary succession
2016
Marine deposits from the Palermo Plain were historically relevant for the Quaternary Period definition. Here we show lithostratigraphic, biostratigraphic and chronostratigraphic data collected on three boreholes in the Palermo historical centre that recovered 36.8, 42.0 and 52.0 metres of sediments overlaying the Numidian Flysch. Marine sedimentary sequences span from the Calabrian Stage (calcareous nannofossil Zone MNN 19d) to the Middle Pleistocene (dominance of medium-sized gephyrocapsids within the MNN 19f Zone) and also include a short Holocene depositional event. Calcareous nannofossil, benthic and planktonic foraminifera assemblages point to a shallow coastal environment, possibly < …
Carbonate slope re‐sedimentation in a tectonically‐active setting (Western Sicily Cretaceous Escarpment, Italy)
2020
Tectonic processes are widely considered as a mechanism causing carbonate platform margin instabilities leading to the emplacement of mass transport deposits and calciturbidites. However, only few examples establishing a clear link between tectonics and re-sedimentation processes are known from the lit- erature. The two-dimensional and three-dimensional wire-cut walls of hun- dreds of quarries extracting ornamental limestones (for example, Perlato di Sicilia) from the Western Sicily Cretaceous Escarpment in Italy expose a series of mass transport deposits. The depositional architecture, spatial facies distri- bution and sedimentary features of these deposits were studied in detail. Thin sec…
Missing Records and Depositional Breaks in French Late Pleistocene Cave Sediments
1993
AbstractCave entrance and rock shelter infillings are positioned within the Pleistocene chronology for three areas of France (northern Alps, Franche-Comté, and Périgord). Despite minor local variations, it is possible to identify regional types with a consistent depositional record over long intervals of time. The interregional variability relates to the frequency and position of the gaps within the infillings. Sites in the northern Alps have not yielded any artifacts older than the Upper Paleolithic (Magdalenı́an), and dated sedimentary sequences do not go back beyond the Older Dryas. More complete sequences in Franche-Comté contain Mousterian industries. Two major gaps occur here, one las…
A Cretaceous carbonate escarpment from Western Sicily (Italy): biostratigraphy and tectono-sedimentary evolution
2020
Abstract The presence of a huge carbonate slope of Cretaceous age is recorded in some imbricated thrust sheets from the Maghrebian fold-and-thrust belt cropping out in northwesternmost Sicily (southern Italy). The sedimentological features of this escarpment, named as the Western Sicily Cretaceous Escarpment (WSCE), have been recently described. The present paper aims to provide a detailed bio-chronostratigraphic characterization of the different facies types that occur in the four lithostratigraphic units spanning the whole slope depositional system. The detailed biostratigraphic analysis and correlation of a number of well-exposed sections allowed to differentiate eight informal biozones …
Does glacial environment produce glacial mineral grains? Pro- and supra-glacial Icelandic sediments in microtextural study
2022
Abstract Mineral grains from proglacial and supraglacial sedimentary settings in central south-eastern Iceland are considered in this study and analysed with the use of scanning electron microscope (SEM) techniques. By applying this, it is attempted to answer the key research question of whether quartz grains that come from a glacial-related sedimentary environment are indeed of glacial origin. The study also attempts to provide a linkage between microtextures produced on coarser and finer grains and to verify whether mineral grains from adjacent cryconite holes are similar or different. The preliminary assumption was that the more intense glacial grain record was based on several glacial a…
Depositional mechanism of the upper Pliocene-Pleistocene shelf-slope system of the western Malta Plateau (Sicily Channel)
2021
Abstract A high resolution seismic stratigraphic study of the western edge of the Malta Plateau (central Mediterranean Sea) was conducted to reconstruct the depositional mechanisms of the shelf-slope system since the end of the Messinian salinity crisis (MSC; 5.3 Ma). The accurate interpretation of a large grid of variable-resolution seismic reflection profiles (multichannel and Sub Bottom) allows us to identify and map a Plio-Quaternary sedimentary sequence overlying the Messinian evaporites. The stratal pattern of this sequence is the result of a clinoform prograding system that constitutes the internal structure of a sedimentary shelf developed in a ramp about 2° slope with bathymetries …