CHARACTERIZATION OF SEDIMENTS DEPOSITED ON THE SIOUX RIDGE OF SOUTHEASTERN SOUTH DAKOTA DURING THE LATE CRETACEOUS PERIOD

2019 ◽  
Author(s):  
Stevie L. Holmes ◽  
2010 ◽  
Vol 148 (2) ◽  
pp. 334-339 ◽  
Author(s):  
ERIC BUFFETAUT ◽  
ATTILA ŐSI ◽  
EDINA PRONDVAI

AbstractThe fragmentary pterosaur material from the Campanian Grünbach Formation (Gosau Group) of Muthmannsdorf (Austria), previously identified as Ornithocheirus buenzeli Bunzel, 1871, is revised. A lower jaw fragment shows a helical type of articulation, which is known in several families of pterosaurs, and cannot be identified with great accuracy. The proximal part of a humerus shows distinctive features that allow it to be referred to as a member of the family Azhdarchidae, which is widespread in the Late Cretaceous Period of Europe. Ornithocheirus buenzeli is considered a nomen dubium. The pterosaur material from the Grünbach Formation cannot be used as evidence for the presence of ornithocheirids in the Late Cretaceous of Europe.


1993 ◽  
Vol 40 ◽  
pp. 9-32
Author(s):  
E. Håkansson ◽  
C. Heinberg ◽  
C. Hjort ◽  
P. Mølgaard ◽  
S. A. S. Pedersen

The 1985 expedition constitutes the first comprehensive investigation of the isolated, hyperarctic semi­nunatak Kilen in eastern North Greenland. Well over 3 km of generally marine, elastic sediments are preserved from the Late Jurassic to Late Cretaceous period. While half this amount accumulated in ·a comparatively stable tectonic regime prevailing during Late Jurassic and Early Cretaceous time, the Late Cretaceous (Turonian-Coniacian) sediments are characterized by their deposition in a local pull-apart basin developed in the regional Wandel Hav Strike-Slip Mobile Belt. Subsequent, localized compression along this belt has deformed the entire sequence rather severely in a complex series of en echelon domal folding and thrusting, most likely during the later part of the Cretaceous. Quaternary marine sediments of probable interglacial origin (> 100.000 years old) have been found to contain a mollusc fauna requiring temperatures above the present level. Flade lsblink, the largest local icecap in Greenland, is composed of several semi-independant ice domes, and there is evidence that the history of this icecap deviates significantly from that of the Inland Ice. A total of 34 species of higher plants, 29 species of birds, and 11 species of mammals have been recorded from Kilen; vegetation studies indicate a July mean temperature of around 2.5°C.


2020 ◽  
Author(s):  
Cunjian Zhang ◽  
Jingdong Liu ◽  
Youlu Jiang

<p>Research on overpressure evolution and its formation mechanisms is of great significance for revealing reservoir formation mechanisms and predicting formation pressures in oil and gas reservoirs before drilling. However, research methods addressing overpressure evolution are not without issues. The fluid inclusion PVT simulation and basin simulation can be used to investigate the paleo-pressure.</p> <p>The homogenization temperatures of inclusions were tested. The accuracy of the microscopic laser Raman spectroscopy analysis is too limited to fully test the components of gaseous hydrocarbon inclusions so that the organic components of the natural gas in the present-day gas reservoirs represented the gaseous hydrocarbon inclusions. In addition, the vapor-liquid ratio of gaseous hydrocarbon inclusions cannot be measured by CLSM. Firstly, A series of images at different slice depths was obtained by adjusting the focal length of a high-resolution microscope. Secondly, CorelDRAW software was used to calculate the areas of inclusions and bubbles; fitting functions were established between the inclusion areas and slice depths, and between the bubble areas and slice depths. Finally, the inclusion and bubble volumes were integrated to obtain the vapor-liquid ratios of the inclusions. PVTsim software can calculate the trapping pressures of inclusions. Combined with basin simulation, the evolution of paleo-pressure can be determined.</p> <p>The above methods were used to investigate the paleo-pressure of the Upper Triassic Xujiahe Formation in the northeast portion of the Sichuan Basin. Overpressure began to develop in the Middle Jurassic period. Due to hydrocarbon generation taking place, the formation pressure increased rapidly from the Middle Jurassic period to the early Late Cretaceous period. Since the early Late Cretaceous period, the formation pressure has gradually decreased due to tectonic uplift and erosion. From the Oligocene period to the present, the formation pressure have increased again in local areas due to tectonic compression.</p>


1994 ◽  
Vol 6 (3) ◽  
pp. 401-408 ◽  
Author(s):  
R. C. R. Willan ◽  
R. J. Pankhurst ◽  
F. Hervé

Fifteen samples of very low-grade mudstones from two widely separated sections in the Miers Bluff Formation on Hurd Peninsula yield an Rb-Sr errorchron (MSWD=8.9) corresponding to an age of 243 ± 8 Ma. This age is interpreted as representing effective homogenization, on a kilometres scale, during turbidite deposition and diagenesis in early Triassic times. The initial 87Sr/86Sr ratio 0.7085 ± 0.0003 represents a mature crustal source and is consistent with the re-working of material comparable to that eroded from the Chilean fore-arc accretionary complex. Four further samples, collected near to a zone of quartz-carbonate veins, lie to the right of the errorchron, with two samples having unusually low Sr contents. These samples fall on a 113 Ma reference line and indicate metasomatic disturbance in Cretaceous times. Metasomatism was probably related to hydrothermal alteration accompanying widespread silicification and quartz veining on western Hurd Peninsula. A mid-to late Cretaceous age for metasomatic disturbance agrees with field relations which indicate that the hydrothermal activity preceded or was coeval with the mid- to late Cretaceous period of volcanism on Livingston Island. Hence the hydrothermal rocks are not related to the Eocene Barnard Point pluton, as previously suggested.


Vista ◽  
2019 ◽  
pp. 217-228
Author(s):  
Victoria Ahrens

This is a visual essay that meanders. It is based around my encounter with palm trees and my grandfather’s silver print photographs, collated in an album that dates back to the 1930s. Henry Richard Ahrens was a keen photographer, though I had never seen any of his images until 2010 when I was given one of his albums by a relative who knew I was a photographer and writer. He died before I could get to know him. His photographs have a particular sensibility to them, with a multitude of self-portraits, and often, a hand written phrase to go with them. I am told he developed his films himself. He is often pictured next to palm trees in his photographs. These palms he photographed are particularly fascinating to me. They represent one of the few genus that extend back to the late Cretaceous period, a dinosaur of a plant species. With their many variations, they take on a poetic and utopian presence, their seeds having been disseminated through colonial exchanges, botanical curiosity and commercial interests. Found in so many surprising corners of the world, the palm expresses our need to explore, while becoming a symbol of resistance to discourses of nationalism and anti-immigration sentiment. This essay reflects a personal ethnography through the interconnected and material presence of the palm in London, Buenos Aires and in the photograph itself.


Nature ◽  
2012 ◽  
Vol 488 (7410) ◽  
pp. 205-208 ◽  
Author(s):  
Nicholas R. Longrich ◽  
Bhart-Anjan S. Bhullar ◽  
Jacques A. Gauthier

2021 ◽  
Author(s):  
Tibor Pecsics

ABSTRACT The first trace fossils in Hungary, dinosaur footprints, were found in the coal mines of the Mecsek Mountains. The footprints belonged to small theropod dinosaurs. The first fossil bones of vertebrate animals from present-day Hungary were found in 2000 in the mountainous region of Bakony. Numerous taxa have been collected from the locality of Iharkút. These fossils represent a diverse fauna (including fishes, amphibians, turtles, lizards, crocodilians, dinosaurs, birds, and pterosaurs) that lived between 85.8 and 83.5 m.y. ago in the Santonian Age during the Late Cretaceous period. Paleoart can depict these fossil remains in an engaging way to help inform the public about the ancient creatures of Hungary. This chapter provides an overview of how the Mesozoic vertebrates from Hungary have been reconstructed for scientists and the public.


Geosciences ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 490
Author(s):  
Mohammed H. N. Al-Kindi

Considering the foreland fold belt of the Salakh Arch in the northern Oman Mountains, predictions made from two-dimensional (2D) restorations and geometrical analyses are tested here to assess the relationship between large-scale folds and small-scale fractures. The Salakh Arch is composed of six anticlines that are interpreted as faulted detachment folds. They have an overall stratigraphy of a 2-km-thick carbonate platform underlain by more than 1.5 km of interbedded sandstone and shale sequences. These sequences are most likely detached on a regionally extensive evaporite horizon. The folding of the Salakh Arch structures most likely occurred during the Neogene Period, and perhaps partly in the early Quaternary Period. This is evident from the thrusting of the Late Neogene Barzaman Formation which was deposited during the Late Neogene Period. Robust outcrop and subsurface fracture data are used to test these predictions. The results from the study indicate that most fractures are related to the orientation of the local structure, with some sets parallel and some sets perpendicular to local hinge lines. Prefolding regional fractures are also widely distributed, and these were mostly formed during the Late Cretaceous Period. Many pre-existing fractures are associated with faults that formed during the Late Cretaceous Period under a NW–SE compression. The local fractures generally have orientations that are consistent with being formed by the flexural slip/flexural flow of fold limbs and tangential longitudinal strains on fold hinges. These structures can be predicted from finite stratal dips, simple curvatures, and three-dimensional (3D) folding restoration maps. The Gaussian curvatures and 3D faulting restoration maps can be used as proxies for fault-related fractures. Local hinge-related fractures may reflect local tangential longitudinal strain during large-scale fold tightening. Fold structures that have formed at an oblique orientation to the regional shortening direction show additional fracture arrays perpendicular to the hinge, indicating weak axial extension. This is presumed to develop as the arcuate thrust belt of Salakh Arch was amplified. The analysis here illustrates the importance of taking a 3D approach, especially for noncylindrical folds. The protocols developed in this study and their results may have general applicability to investigations of fracture patterns in other folds.


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