Shortening history of the Neoproterozoic oroclinal bending in Paraguay belt, Central Brazil, based on structural interpretation of field work and high resolution aerogeophysical data

Author(s):  
Marcelo Ferreira da Silva ◽  
Elton Luiz Dantas ◽  
Roberta Mary Vidotti
Author(s):  
Adam A. Garde ◽  
Brian Chadwick ◽  
John Grocott ◽  
Cees Swager

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Garde, A. A., Chadwick, B., Grocott, J., & Swager, C. (1997). Metasedimentary rocks, intrusions and deformation history in the south-east part of the c. 1800 Ma Ketilidian orogen, South Greenland: Project SUPRASYD 1996. Geology of Greenland Survey Bulletin, 176, 60-65. https://doi.org/10.34194/ggub.v176.5063 _______________ The south-east part of the c. 1800 Ma Ketilidian orogen in South Greenland (Allaart, 1976) is dominated by strongly deformed and variably migmatised metasedimentary rocks known as the ‘Psammite and Pelite Zones’ (Chadwick & Garde, 1996); the sediments were mainly derived from the evolving Julianehåb batholith which dominates the central part of the orogen. The main purpose of the present contribution is to outline the deformational history of the Psammite Zone in the region between Lindenow Fjord and Kangerluluk (Fig. 2), investigated in 1994 and 1996 as part of the SUPRASYD project (Garde & Schønwandt, 1995 and references therein; Chadwick et al., in press). The Lindenow Fjord region has high alpine relief and extensive ice and glacier cover, and the fjords are regularly blocked by sea ice. Early studies of this part of the orogen were by boat reconnaissance (Andrews et al., 1971, 1973); extensive helicopter support in the summers of 1992 and 1994 made access to the inner fjord regions and nunataks possible for the first time.A preliminary geological map covering part of the area between Lindenow Fjord and Kangerluluk was published by Swager et al. (1995). Hamilton et al. (1996) have addressed the timing of sedimentation and deformation in the Psammite Zone by means of precise zircon U-Pb geochronology. However, major problems regarding the correlation of individual deformational events and their relationship with the evolution of the Julianehåb batholith were not resolved until the field work in 1996. The SUPRASYD field party in 1996 (Fig. 1) was based at the telestation of Prins Christian Sund some 50 km south of the working area (Fig. 2). In addition to base camp personnel, helicopter crew and the four authors, the party consisted of five geologists and M.Sc. students studying mafic igneous rocks and their mineralisation in selected areas (Stendal et al., 1997), and a geologist investigating rust zones and areas with known gold anomalies.


2020 ◽  
Author(s):  
Sookwan Kim ◽  
Leonid Polyak ◽  
Young Jin Joe ◽  
Frank Niessen ◽  
Hyoung Jun Kim ◽  
...  

1998 ◽  
Vol 17 (2) ◽  
pp. 153-172 ◽  
Author(s):  
Raffaella Bucefalo Palliani ◽  
Emanuela Mattioli

Abstract. The integrated use of calcareous nannofossil and dinoflagellate cyst events in a study of the late Pliensbachian–early Toarcian interval in central Italy has yielded a high resolution biostratigraphy. The use of both the first and last occurrences of selected taxa belonging to the two phytoplankton groups allows the dating of the sediments with a very refined detail, even when lithologies are unfavourable to the preservation of one fossil group. The evolutionary history of calcareous nannofossils and dinoflagellate cysts during the early Jurassic and its links with global events are responsible for the high potential of this integrated biostratigraphy.


2018 ◽  
Vol 39 (12) ◽  
pp. 2231-2236 ◽  
Author(s):  
M. Trelles ◽  
A.K. Ahmed ◽  
C.H. Mitchell ◽  
I. Josue-Torres ◽  
D. Rigamonti ◽  
...  

1994 ◽  
Vol 20 ◽  
pp. 55-60
Author(s):  
Anja L.L.M. Verbers ◽  
Volkmar Damm

Glacio-geological field work and radar ice-thickness sounding were carried out in the area between David and Mawson Glaciers. A subglacial topographic map has been compiled from radio-echo-sounding data. The northern part of this map shows that the trench of David Glacier reaches a depth of more than 1000 m below sea level. The area south of David Glacier comprises a landscape of nunatak clusters dissected by glaciated valleys with ice thicknesses as much as 800 m. Subglacial cirques occur at the outer margins of the nunatak clusters. A model for the regional glacial history is proposed. It starts with a major deglaciation in the Pliocene, which results in marine transgression in basins west of the Transantarctic Mountains. During the late Pliocene, the ice advanced towards the northeast, depositing a thin layer of (Sirius Group) till containing reworked mid-Pliocene marine diatoms. Due to accelerated mountain uplift, the ice cut iIlto the pre-Pliocene peneplain, eroding broad valleys. A period of ice-sheet retreat followed to expose a landscape of large nunataks separated by wide valleys. During this period, local cirque glaciation occurred. When the ice sheet advanced again, another phase of uplift forced the glaciers to cut deeper into the valleys. Probably since the Last Glacial Maximum the ice surface has lowered by about 100 m.


2010 ◽  
Vol 67 (11) ◽  
pp. 945-948 ◽  
Author(s):  
Djula Djilvesi ◽  
Petar Vulekovic ◽  
Tomislav Cigic ◽  
Zeljko Kojadinovic ◽  
Vladimir Papic ◽  
...  

Introduction. A gunshot head injury, characterized by a huge intensity of mechanical force, in addition to the direct tissue damage at the location of direct impact, may cause a skull and skull base fracture, distant from the the point of direct impact, which could be further complicated by creating a communication between endocranium and nasal/paranasal cavities. Such cases pose a great diagnostic and therapeutic challenge for every clinician. Case report. The patient is presented with the history of a perforating gunshot head injury six years ago, with recurrent attacks of meningoencephalitis subsequently, without rhinorrhea. By using high resolution CT scans, previous traumatic skull injury was verified and a fissure in the frontoethmoidal region, far from the point of direct impact, was detected. The patient underwent transnasal endoscopic surgery, in order to seal the communication on skull basis. The patient did not suffer from meningoencephalitis during the next two years. Conclusion. In the cases with late occurrence of posttraumatic meningoencephalitis with no signs of rhinorrhea, a possibility of an existing communication between intracranial and nasal cavities should be considered, as well. By applying modern diagnostic and therapeutic procedures such communication should be precisely located and sealed.


2021 ◽  
Vol 922 (2) ◽  
pp. 256
Author(s):  
Giulia Perotti ◽  
Henning O. Sørensen ◽  
Henning Haack ◽  
Anja C. Andersen ◽  
Dario Ferreira Sanchez ◽  
...  

Abstract Protoplanetary disks are dust- and gas-rich structures surrounding protostars. Depending on the distance from the protostar, this dust is thermally processed to different degrees and accreted to form bodies of varying chemical compositions. The primordial accretion processes occurring in the early protoplanetary disk such as chondrule formation and metal segregation are not well understood. One way to constrain them is to study the morphology and composition of forsteritic grains from the matrix of carbonaceous chondrites. Here, we present high-resolution ptychographic X-ray nanotomography and multimodal chemical microtomography (X-ray diffraction and X-ray fluorescence) to reveal the early history of forsteritic grains extracted from the matrix of the Murchison CM2.5 chondrite. The 3D electron density maps revealed, at unprecedented resolution (64 nm), spherical inclusions containing Fe–Ni, very little silica-rich glass and void caps (i.e., volumes where the electron density is consistent with conditions close to vacuum) trapped in forsterite. The presence of the voids along with the overall composition, petrological textures, and shrinkage calculations is consistent with the grains experiencing one or more heating events with peak temperatures close to the melting point of forsterite (∼2100 K), and subsequently cooled and contracted, in agreement with chondrule-forming conditions.


Antiquity ◽  
1963 ◽  
Vol 37 (147) ◽  
pp. 176-184 ◽  
Author(s):  
Hsia Nai

Archaeology as a branch of historical science has made new headway in the thirteen years since the founding of the Chinese People's Republic. The scale of its work has expanded and methods of research have been improved. Large numbers of young archaeological workers have been trained. In the course of the nation's gigantic economic construction, remains of ancient settlements and tombs have been uncovered in many places, yielding numerous important relics which have provided abundant data for archaeological research. Throughout the country, hosts of archaeological workers from research institutes, universities, museums and institutions for the preservation of ancient monuments are carrying out both field work and academic study and have already attained considerable success in their efforts to explore the history of ancient China on the basis of archaeological finds. All this has given further impetus to the advance of Chinese archaeology.Archaeological finds made in New China are so rich that the present article can attempt to discuss only some of the most important problems.


1978 ◽  
Vol 35 (2) ◽  
pp. 219-237
Author(s):  
J. Manuel Espinosa

The centuries-old Spanish folk heritage of our Southwest, and its many faceted and enduring influence on the cultural life of the region, has been written about from various rims of observation. This article describes the pioneer studies of Aurelio M. Espinosa on Spanish folklore in the Southwest, with special emphasis on northern New Mexico. Although he made important contributions to the study of Spanish folklore of southern Colorado, Arizona, and California, and to that of Spain, Mexico, and other parts of Spanish America as well, he devoted most of his research and field work to the upper half of New Mexico which is the richest field of Spanish folklore in the Southwest.In viewing the cultural history of New Mexico, Espinosa reminded his readers that its first century as a Spanish colony, the 17th, was the second great century of Spain's Golden Age of arts and letters. With the vigor of Spain's sense of mission in those centuries, her Golden Age radiated to all parts of Spanish America via Mexico City, Lima, and the other principal colonial capitals. At the same time, from the bookshelf and the store of knowledge of the humble missionary, and the folklore of the Spanish settlers, passed down from generation to generation, the spirit of the Golden Age was reflected on the most remote settled frontiers.


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