Search results for "Outcrop"
showing 10 items of 101 documents
Analysis of a complex high-strain zone at Cap de Creus, Spain
1997
Abstract The structural analysis of a high-strain zone developed in medium- to high-grade metamorphic micaschists from the Cap de Creus area, Spain provides an example of the complex relationships between geometry, strain and kinematics to be found in deep crustal shear zones. This high-strain zone is composed of E-W trending structural domains characterized by different strain intensities and associated with syntectonic emplacement of pegmatite dykes. The main phase of deformation discussed here, D2, affects steeply dipping bedding, boudinaged quartz veins and S1 developed parallel to bedding. D2 deformation of these features and of syn-D2 pegmatite dykes gives rise to fold/boudin structur…
Flow and Deformation
1998
A hunter who investigates tracks in muddy ground near a waterhole may be able to reconstruct which animals arrived last, but older tracks will be partly erased or modified. A geologist faces similar problems to reconstruct the changes in shape that a volume of rock underwent in the course of geological time, since the end products, the rocks that are visible in outcrop, are the only direct data source. In many cases it is nevertheless possible to reconstruct at least part of the tectonic history of a rock from this final fabric. This chapter treats the change in shape of rocks and the methods that can be used to investigate and describe this change in shape. This is the field of kinematics,…
Synsedimentary-tectonic, soft-sediment deformation and volcanism in the rifted Tethyan margin from the Upper Triassic–Middle Jurassic deep-water carb…
2014
Abstract The Pizzo Lupo section (Sicanian Mts, central Sicily) is an Upper Triassic–Lower Jurassic condensed deep-water succession, where the relationships among synsedimentary tectonic, soft-sediment deformations, volcanism and lithological changes reflect the evolution of a rift-basin. The morphostructural setting of the studied basin appears as a gently dipping slope where a fault-delimited area (graben to halfgraben) was developed. The instability of the sea floor, related to the seismic shocks, was the cause of the gravity-driven deformational sedimentary structures (slumping, breccia channelized bodies). The partly stratified basaltic rocks, with disorganized and chaotic stratificatio…
Early Cretaceous termites in amber from northern Spain (Isoptera)
2020
Abstract Two virtually complete termites in Lower Cretaceous amber from the Penacerrada I outcrop, Spain, are described and figured, representing the most well-preserved Isoptera yet discovered from the Albian stage. The material is described as Ithytermes montoyai gen. et sp. nov., and is similar in many details to the slightly younger Krishnatermes yoddha Engel, Barden, and Grimaldi from northern Myanmar amber. Given the presence of distinct soldiers in this grade of Cretaceous termites, it is likely that I. montoyai also exhibited such a tripartite caste system. In addition to the type material of I. montoyai, two fragmentary termites are recorded for the first time in Albian amber from …
3D visualization of sheath folds in Ancient Roman marble wall coverings from Ephesos, Turkey
2014
Abstract Archaeological excavations and restoration of a palatial Roman housing complex in Ephesos, Turkey yielded 40 wall-decorating plates of folded mylonitic marble (Cipollino verde), derived from the internal Hellenides near Karystos, Greece. Cipollino verde was commonly used for decoration purposes in Roman buildings. The plates were serial-sectioned from a single quarried block of 1,25 m3 and provided a research opportunity for detailed reconstruction of the 3D geometry of meterscale folds in mylonitized marble. A GOCAD model is used to visualize the internal fold structures of the marble, comprising curtain folds and multilayered sheath folds. The sheath folds are unusual in that the…
Middle to Upper Pleistocene morphostructural evolution of the NW-coast of Sicily: thermoluminescence dating and palaeontological-stratigraphical eval…
1997
Abstract Infralittoral and terrigenous Middle to Upper Pleistocene deposits outcropping at the NW-coast of Sicily (Gulf of Castellammare and peninsula of Capo San Vito) were investigated in order to recognise glacio-eustatically caused sea level highstands and the interference between tectonics, eustasy and local conditions of the coast. The results, originating from a stratigraphically important area, were obtained by palaeontological-stratigraphical analyses, physical age determination with the thermoluminescence method and by detailed morphostructural studies. The marine deposits, situated at 3–40 m a.s.l., mainly provide an oligotypic molluscan fauna referable to modern SGCF-, SFHN- and…
The Phycosiphon record in the Ladrilleros-Juanchaco section (Miocene, Colombian Pacific): palaeoecological implications
2018
Miocene rocks of the Ladrilleros-Juanchaco section, located on the NW margin of South America, contain a high diverse and abundant trace fossil assemblage. The relative abundance of Phycosiphon, together with its morphological variations, provides new insights into the environmental conditions. Detailed outcrop stratigraphic, ichnological, and geochemical analyses carried out in the section focused on the trace fossil assemblages (distribution, relative abundance), ichnofabric index, and, especially, in the general ichnological features of Phycosiphon . In addition, the detailed photographic documentation and the use of the digital image treatment technique facilitate the precise study of …
Variation in structural styles within fold-and-thrust belts: Insights from field mapping, cross-sections balancing, and 2D-kinematic modelling in the…
2021
Abstract Fold-and-thrust belts developed above an evaporite decollement host structural traps where geofluids, including hydrocarbons, can accumulate. A valid and accurate structural style intepretation is therefore crucial to understand the three-dimensional geometries in the subsurface, in order to better model geofluid reservoirs and to increase success during exploration. Here, we present a multidisciplinary approach to unravel the subsurface structural styles of the Jura fold-and-thrust belt (eastern France), combining geological mapping, from regional to outcrop scale, with cross-section balancing and 2D-kinematic forward modelling. Results show that the Jura fold-and-thrust belt is c…
Anza palaeoichnological site, Late Cretaceous, Morocco. Part III: Comparison between traditional and photogrammetric records
2020
11 pages; International audience; The present study evaluates a methodological workflow that could identify dinosaur tracks and trackways more comprehensively at outcrop scale. The approach described here is based both on 3D modelling by photogrammetry at different resolutions, and on suitably processed digital elevation models (DEMs). The ichnosite of Anza, Morocco, was chosen to demonstrate the efficiency of the proposed pipeline, because 323 dinosaur and pterosaur tracks discovered there have already been published. One subsector containing 89 tracks, identified in the two companion works that followed a traditional approach, was selected and divided into four subzones. By combining diff…
Cenomanian rudist-dominated shelf-margin limestones from the Panormide carbonate platform (Sicily, Italy): facies analysis and sequence stratigraphy
2000
Sedimentological, paleontological and sequence analyses of Cenomanian limestones in Sicily reveal thc facies architecture and dynamics of a Mid Cretaceous rudistdominated platform margin from Western Tethys. The studied deposits outcrop near Palermo, as part of a large structural unit of the Sicilian Maghrebids. They belong to the Panormide carbonate platform, a Mesocenozoic paleogeographic domain of the African margin. The lateral continuity of the beds along three nearly parallel E-W outcrop sections allowed the recording of cm/dm thick lithological and faunal variations. Nine main lithofacies associations have been recognised along about 200 m of subvertical strata. Their vertical and la…