نتایج جستجو برای: cretaceous rocks
تعداد نتایج: 30195 فیلتر نتایج به سال:
Three teeth of the shark Serratolamna serrata (Agassiz) from the Guinea Corn Formation (Central Inlier) represent the first recorded occurrence of fossil sharks from Cretaceous rocks of Jamaica. This occurrence increases the known palaeogeographical distribution of S. serrata, which appears to have been global. This species is largely known from the Upper Maastrichtian, which helps confirm the ...
The term "black shale" is a common expression widely used to describe any dark~olored, fine-grained sedimentary rock relatively rich in organic matter. As defined by Weissert (1981), the range of organic carbon in black shales is between 1 and 30%, but values outside this range exist. The term usually connotes at least partial lithification, yet this may not be true in young, shallow sediments....
Bimodal volcanism in the Santa Maria Province of west-central California occurred when segments of the East Pacific Rise interacted with a subduction zone along the California margin during the Early Miocene (about 17 million years ago). Isotopic compositions of neodymium and strontium as well as trace-element data indicate that these volcanic rocks were derived from a depleted-mantle (mid-ocea...
Undiscovered, conventional oil and gas resources were assessed in the Senegal Province as part of the U.S. Geological Survey World Petroleum Assessment 2000 (U.S. Geological Survey World Energy Assessment Team, 2000). Although several total petroleum systems may exist in the province, only one composite total petroleum system, the CretaceousTertiary Composite Total Petroleum System, was defined...
This paper presents evidence on Mesozoic inversion of basin bounding faults within the Taleqan-Gajereh-Lar Paleograben (TGLP) in Central Alborz Range. For this purpose, well documented stratigraphy data across the TGLP together with the new acquired structural data on the geometry and kinematics of the paleograben basin bounding faults are utilized. The TGLP has evolved through the Early and Mi...
The mineralogy and geochemistry of Paleocene shales and interbedded siltstones in the southwestern of Ahar town (NW Iran) were studied by optical microscopy, XRD, SEM, XRF, and ICP-MS techniques. The mineralogical composition, mainly characterized by calcite, quartz, feldspar, dolomite, muscovite, magnesiohornblende, chlorite, illite, montmorionite, palygorskite, and koninckite, suggests relati...
We present thermodynamic estimates of pressures, temperatures, and volatile activities in vailably deformed, gabbroic to granitic, Cretaceous (115-100 Ma) batholithic and framework rocks of the Tehachapi Mountains, southernmost Sierra Nevada, California. A1 contents of hornblende in granitoids imply igneous emplacement at --8 kbar in the southernmost Tehachapi Mountains, with lower pressures (3...
INTRODUCTION The rocks on the Greek island of Syros are part of a suite of high pressure metamorphic rocks which outcrop all across the Cyclades. There is a complex metamorphic history recorded in the rocks here, including a Cretaceous or Eocene high-pressure blueschist event and a Miocene, extension-related greenschist overprint. The Island of Syros is mostly composed of schists , which altern...
The Southern Caspian Sea ophiolite complex (SCO) is one of the Late Cretaceous discontinuous oceanic lithosphere remnants in northern Iran. These complex is almost a complete sequence from bottom to top, ultramafic cumulates, layered gabbros, isotropic gabbros, dike complex and basaltic lavas which is covered by Late Cretaceous (Companion- maaestirchtian) pelagic limestone. Crustal ultramafic c...
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