Search results for "cretaceous"
showing 10 items of 182 documents
Neocomian to early Aptian syn-rift evolution of the normal to oblique-rifted North Gabon Margin (Interior and N'Komi Basins).
2009
18 pages; International audience; The North Gabon coastal rift basins consist of a set of 130–150 long-segment asymmetrically tilted half grabens (Interior Basin) and 000–020 short-segment en échelon half grabens (N'Komi Basin) separated by 040–060 major transverse faults. Tectono-sedimentary analysis of field and subsurface data reveals the control exerted by extensional tectonism over continental sedimentation. During Berriasian to early Barremian times, uniform uniaxial 040–060 extension was responsible for the stretching of the brittle upper crust over a 100-km wide domain. During late Barremian–early Aptian times, the main locus of extension stepped westward resulting in severe end-rif…
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…
A record of seafloor methane seepage across the last 150 million years
2020
<p>Methane seepage at the seafloor is a source of carbon in the marine environment and has long been recognized as an important window into the deep geo-, hydro-, and bio-spheres. However, the processes and temporal patterns of natural methane emission over multi-million-year time scales are still poorly understood. The microbially-mediated methane oxidation leads to the precipitation of authigenic carbonate minerals within subseafloor sediments, thus providing a potentially extensive record of past methane emission. In this study, we used data on methane-derived authigenic carbonates to build a proxy time series of seafloor methane emission over the last 150 My. We quantitat…
Environmental change during the Early Cretaceous in the Purbeck-type Durlston Bay section (Dorset, Southern England): a biomarker approach.
2007
20 pages; International audience; The Purbeck-type section (Durlston Bay, Dorset, UK) exhibits littoral lagoonal to lacustrine facies. It shows a gradual climatic/environmental change from semi-arid conditions associated with evaporites at the Jurassic–Cretaceous transition, to a more humid climate at the end of the Berriasian. Though generally organic-poor (total organic carbon, TOC, <1.3%), the Durlston Bay section shows an organic-rich episode (TOC up to 8.5%) located at the transition from evaporitic to more humid facies. A biomarker study was performed in order to determine the origin of the organic matter (OM) in the section and see if changes in organic sources accompanied the genera…
Impact of basin burial and exhumation on Jurassic carbonates diagenesis on both sides of a thick clay barrier (Paris Basin, NE France).
2014
27 pages; International audience; Several diagenetic models have been proposed for Middle and Upper Jurassic carbonates of the eastern Paris Basin. The paragenetic sequences are compared in both aquifers to propose a diagenetic model for the Middle and Late Jurassic deposits as a whole. Petrographic (optical and cathodoluminescence microscopy), structural (fracture orientations) and geochemical (δ18O, δ13C, REE) studies were conducted to characterize diagenetic cements, with a focus on blocky calcite cements, and their connection with fracturation events. Four generations of blocky calcite (Cal1-Cal4) are identified. Cal1 and Cal2 are widespread in the dominantly grain-supported facies of t…
Incised valleys and tidal seaways: the example of the Miocene Uzès-Castillon basin, SE France.
2012
Abstract The sedimentology and stratigraphy of the Miocene deposits of the Uzès-Castillon basin are revisited. This basin, located in SE France at the junction between the perialpine foreland basin and the W Mediterranean margin, sits in a syncline that formed during the latest Cretaceous Pyrenean tectonic phase. It records the succession of shallow-water mixed siliciclastic to dominantly bioclastic carbonates that alternate with shelf marls. The clastic carbonates were accumulated as a stack of subtidal dunes and bars that were formed by tidal currents channelized in a seaway following the syncline axis. The marls indicate deposition in more protected and locally deeper waters, as interflu…
Numerical evidence for thermohaline circulation reversals during the Maastrichtian
2005
[1] The sensitivity of the Maastrichtian thermohaline circulation to the opening/closing of marine communications between the Arctic and North Pacific oceans is investigated through a set of numerical experiments using the model CLIMBER-2 (Earth Model of Intermediate Complexity). We show here that the opening or closing of an Arctic-Pacific marine gateway induces transitions between different equilibrium states of the thermohaline circulation. Sensitivity tests of the inferred modes of thermohaline circulation to atmospheric CO2 level changes have also been explored. An abrupt switch in deep convection from high northern to high southern latitudes, a change consistent with isotopic evidence…
Fluid storage and migration properties of sheared Neptunian dykes
2019
Abstract Neptunian dykes are widely reported along the Tethyan carbonate platforms and are commonly considered as subsurface baffles or barriers to fluid flow. However, the fluid storage and migration properties of sheared Neptunian dykes are poorly known. For this reason, we investigate the inner structure and fluid flow properties of two Neptunian dykes, which can be characterized by different architectures if involved or not in brittle shearing processes. The dykes strike ca. WNW-ESE and crosscutting the tight Jurassic limestones exposed at Maranfusa Mt., NW Sicily, Italy. The unsheared and sheared Neptunian dykes are almost sub-vertical and at high-angle with respect to the horizontal p…
The giant inoceramid Platyceramus platinus as a high-resolution paleoclimate archive for the Late Cretaceous of the Western Interior Seaway
2018
Abstract Platyceramus platinus was a giant inoceramid bivalve that inhabited the outer shelf environments of the Western Interior Seaway (WIS) in North America. With axial heights typically exceeding 1 m, the shells of this species potentially serve as a unique high-resolution geochemical proxy archive for Late Cretaceous paleoclimate. Here we present the first sclerochronological investigation of P. platinus shells to evaluate the usefulness of this species as an archive of short-term (e.g., seasonal to inter-annual) paleoenvironmental variability. We analyzed the growth patterns, the stable oxygen (δ18O) and carbon (δ13C) isotope values of well-preserved P. platinus shell fragments from t…
Cretaceous ultrapotassic magmatism from the Sava-Vardar Zone of the Balkans
2020
Highlights • Geochemically diverse Late Cretaceous small-volume magmatism in the Sava-Vardar Zone. • Late Cretaceous ultrapotassic lava, equivalent of minette and kersantite. • Magma derivation from a LREE and K enriched, garnet-bearing anciently metasomatized mantle source. • Magmatism occurred either in a fore-arc setting or is associated with transtensional tectonics. Abstract Late Cretaceous global plate reorganization associated with the inception of counterclockwise rotation of Africa relative to Europe initiated in the Balkan region small-volume magmatism of diverse geochemical signature along the enigmatic Sava-Vardar Zone. We study a Late Cretaceous lamprophyric sill in Ripanj vill…