Search results for "conformity"

Middle Jurassic–Early Cretaceous tectono-sedimentary evolution of the southwestern Iberian Basin (central Spain): Major palaeogeographical changes in…

2019

Abstract The Middle Jurassic-Early Cretaceous tectono-sedimentary evolution of the southwestern part of the intraplate Iberian Basin (Spain) was mostly controlled by the Alto Tajo-Montes Universales (ATMU) and Landete-Teruel (LT) faults. During the Middle Jurassic, the ATMU fault separated a western area dominated by shallow marine carbonates, and an eastern area with open marine facies. During the Bathonian-Callovian, the area located to the west of the ATMU fault and north of the LT fault (Cuenca domain) was progressively exposed, and remained uplifted until the late Barremian. A widespread unconformity with a variable gap around the Callovian to mid-Oxfordian has been related to the onse…

2021

Intracratonic basins tend to subside much longer than the timescale predicted by thermal relaxation of the lithosphere. Many hypotheses have been suggested to explain their longevity, yet few have been tested using quantitative thermo-mechanical numerical models, which capture the dynamic of the lithosphere. Lithospheric-scale geodynamic modelling preserving the tectono-stratigraphic architecture of these basins is challenging because they display only few kilometres of subsidence over 1000 of km during time periods exceeding 250 Myr. Here we present simulations that are designed to examine the relative role of thermal anomaly, tectonics and heterogeneity of the lithosphere on the dynamics …

The ~2730 Ma onset of the Neoarchean Yilgarn Orogeny

2017

The timing of the onset of an orogeny is commonly constrained indirectly, because early orogenic structures are rarely exposed, or are overprinted. Establishing the onset of an Archean orogeny is considerably more challenging, because of the more fragmented geological record and the general lack of consensus about Archean geodynamics. We combine existing tectono-stratigraphic data with new structural and geophysical datasets to establish the onset of the Neoarchean Yilgarn Orogeny (Yilgarn Craton, Western Australia). We show that the surface of the c. 2960–2750 Ma deep-marine Yilgarn greenstone sequence was uplifted, eroded and unconformably overlain by a c. 2730 Ma, syntectonic clastic seq…

Geodynamic control on carbonate diagenesis: Petrographic and isotopic investigation of the Upper Jurassic formations of the Paris Basin (France).

2007

23 pages; International audience; The Oxfordian and Kimmeridgian carbonates of the eastern edge of the Paris Basin display poor reservoir properties (Φb15% and Kb0.1 md). The petrographic investigation and the resultant paragenetic sequence show that this is due to extensive precipitation of 2 types of almost synchronous blocky LMC (Low Magnesian Calcite) cements during mesogenesis (burial). Stable isotope investigation of these non-recrystallized cements, through both microdrilling sampling and in-situ SIMS (Secondary IonMass Spectrometry) analysis, shows that they originated from slightly buffered meteoric fluids (−3‰SMOW to −8‰SMOW) flowing through the Malm carbonate aquifers of the east…

Landscape instability at the end of MIS 3 in western Central Europe : evidence from a multi proxy study on a Loess-Palaeosol-Sequence from the easter…

2019

Abstract The Lower Rhine Embayment hosts important Loess-Palaeosol-Sequences (LPS) within the western European loess belt yielding valuable information on landscape evolution and palaeoclimatic dynamics. The study focusses on the palaeoenvironmental development based on a LPS from the eastern shoulder of the Lower Rhine Embayment (Dusseldorf-Grafenberg). The palaeoenvironmental development within the study area is presented and discussed based on high-resolution grain size analyses, selected environmental magnetic parameters, and geochemical analyses complemented by luminescence age estimates. Differences in grain size distribution (ΔGSD) as well as the U-ratio clearly reflect main stratigr…

Pre-Hirnantian (latest Ordovician) benthic community assemblages: controls and replacements in a siliciclastic-dominated platform of the eastern Anti…

2007

17 pages; International audience; Lower-middle Ashgill sedimentary strata from the Mediterranean region have recorded a key episode of temperate-to-cold water, carbonate productivity predating the onset of the Hirnantian glaciation. The latitudinal position of the Moroccan margin of North Gondwana during Ashgill should have been adequate for the recorded development of carbonate factories. However, carbonate productivity was neither homogeneous nor laterally persistent, as documented in the eastern Anti-Atlas. Whereas in the Erfoud area, the bryozoan-dominated limestones of the Ashgill Khabt-el-Hajar Formation indicate the intensive activity of carbonate factories, these were dramatically r…

Tectonic evolution of the northern Austral-Magallanes basin in the Southern Patagonian Andes from provenance analysis

2019

We studied the northern tip of the Austral-Magallanes basin in the Southern Patagonian Andes, between the Buenos Aires Lake and the Mayer River at 46°35′ SL and 48°35′ SL, respectively. Proposed objectives were: i) to differentiate Mesozoic-Cenozoic tectonostratigraphic units and, ii) to characterize the different deformational events that took place in the area linked to a variable regional geodynamic context. Sandstones provenance analysis was performed on the Aptian - Albian compressive retroarc deposits and Cenozoic foreland deposits. Studied samples were classified using tectonic discrimination diagrams which show: i) for Cretaceous rocks a dominant sediment source from a recycled orog…

Paleoclimate and extensional tectonics of short-lived lacustrine environments. Lower Cretaceous of the Panormide Southern Tethyan carbonate platform …

2017

Abstract Subaerial erosion and continental sedimentation interbedded with shallow-water carbonates are unequivocal stratigraphic records to evaluate paleoenvironmental and paleoclimate evolution of emerged landmass. Stratigraphic analysis of the Cretaceous Monte Gallo section of the Mesozoic Panormide carbonate platform, in the northern side of the Palermo Mountains (NW Sicily) records a peculiar continental-derived clays that interrupted the shallow-water carbonate sedimentation. These clays rest, with lenticular geometries, above the tectonically-enhanced subaerial erosional unconformity of the Barremian-Lower Aptian Requienid limestones and are covered by the Upper Cretaceous Rudistid li…

Quaternary marine and continental unconformity-bounded stratigraphic units of the NW Sicily coastal belt

2017

In the coastal sector of NW Sicily, the regional correlation of relevant unconformities recognised within the Quaternary sedimentary successions allowed the mapping of seven unconformity-bounded stratigraphic units (UBSUs). The regional unconformities are marine or subaerial erosional surfaces, as well as non-depositional surfaces, locally marked by paleosoils. The erosional surfaces were produced from marine abrasion, surface water overland/concentrated flow, river erosion, karst solution, mass movement, or wind erosion. The main lithofacies of the Quaternary UBSUs consist of: (a) marine and coastal bioclastic calcarenites, (b) aeolian sandstones, (c) river deposits, (d) colluvial deposits…

Dosimetric Impact of Interfractional Variations in Prostate Cancer Radiotherapy—Implications for Imaging Frequency and Treatment Adaptation

2019

Background and purpose: To analyze deviations of the applied from the planned doses on a voxel-by-voxel basis for definitive prostate cancer radiotherapy depending on anatomic variations and imaging frequency. Materials and methods: Daily in-room CT imaging was performed in treatment position for 10 patients with prostate cancer undergoing intensity-modulated radiotherapy (340 fraction CTs). Applied fraction doses were recalculated on daily images, and voxel-wise dose accumulation was performed using a deformable registration algorithm. For weekly imaging, weekly position correction vectors were derived and used to rigidly register daily scans of that week to the planning CT scan prior to d…