The Chitradurga greenstone succession in south India and evolution of the late Archaean basin

1988 ◽  
Vol 125 (5) ◽  
pp. 507-519 ◽  
Author(s):  
P. K. Bhattacharyya ◽  
H. N. Bhattacharya ◽  
A. D. Mukherjee
Keyword(s):  
South India ◽  
Subsequent Development ◽  
Low Grade ◽  
Late Archaean ◽  
Clastic Sediments ◽  
Granitic Intrusion ◽  
Near Shore ◽  
Extensional Faulting ◽  
Wilson Cycle ◽  
Similar Deformation

AbstractThe Chitradurga greenstone succession of south India comprises a thick pile (~ 10 km) of late Archaean volcanic flows and terrigenous clastic sediments, metamorphosed from greenschist to low-grade amphilobite facies. An older near-shore sedimentary sequence of cratonic affiliation and an off-shore bimodal volcanic sequence were deposited contemporaneously on a gneissic basement. The volcanics are metasomatically altered, and major, minor and trace element data fail to discriminate the metavolcanics in terms of modern plate settings. A younger turbidite sequence of coarser elastics covered the older deposits without any apparent tectonic or erosional break. All the rocks of the succession display evidence of similar deformation, prior to invasion by younger granites (~ 2.5 Ga)in a late syn-kinematic phase.This suggests that initially a simple flat-lying downwarp in a continental crust served as the passive receptacle of the platform-type sediments, and also witnessed volcanism along extensional faulting. This phase of the basin was not associated with any compressive deformation. Subsidence of the Chitradurga basin by the denser volcanics and uplift in the gneissic borderlands provided the infrastructure for subsequent development of the younger turbidite sequence covering the still virtually undeformed older deposits. A compressive orogeny, accompanied by granitic intrusion (~ 2.5Ga) in a late kinematic phase, ultimately deformed and uplifted the basin-fill during the declining phase of basinal activity.There is no evidence in the belt to suggest that the plate-tectonic (Wilson cycle) processes, pending a terminal orogeny, were operative during evaluation of the Chitradurga basin.

Shoreline Changes and Near Shore Processes Along Ennore Coast, East Coast of South India

2004 ◽  
Vol 203 ◽  
pp. 828-845 ◽  
Author(s):  
P. Kasinatha Pandian ◽  
S. Ramesh ◽  
M. V Ramana Murthy ◽  
S. Ramachandran ◽  
S. Thayumanavan
Keyword(s):  
South India ◽  
East Coast ◽  
Shoreline Changes ◽  
Near Shore

TECTONIC EVOLUTION OF THE NORTHERN CANADIAN CORDILLERA

1967 ◽  
Vol 4 (2) ◽  
pp. 271-298 ◽  
Author(s):  
H. Gabrielse
Keyword(s):  
Marked Change ◽  
Rocky Mountain ◽  
Late Triassic ◽  
Canadian Cordillera ◽  
Crustal Shortening ◽  
Southern Rocky Mountains ◽  
Structural Style ◽  
Clastic Sediments ◽  
Granitic Intrusion ◽  
Tectonic Framework

A tectonic framework that was established in the northern and eastern parts of the northern Canadian Cordillera in the late Proterozoic persisted generally until mid-Devonian time. Late Palaeozoic deposition was strongly influenced by a late Devonian and (or) early Mississippian orogeny, which produced coarse clastic sediments in the northern and western parts of the region, and by a late Pennsylvanian (?) orogeny evident in northern Yukon. The Cassiar and Coast geanticlines were established at least by late Triassic time and controlled the distribution and character of Mesozoic strata southwest of Tintina and Rocky Mountain Trenches.Metamorphism and granitic intrusion were concentrated along Cassiar and Coast Geanticlines. During the Mesozoic and early Tertiary, plutonic activity appears to have occurred at intervals of about 30 million years and was accompanied generally by deformation and development of regional unconformities. Crustal shortening has been much less in Mackenzie Mountains than in southern Rocky Mountains; a marked change in structural style of the eastern Cordillera occurs near Liard River. Many phases of deformation and intrusion have affected rocks in the southwestern part of the region; their differentiation is as yet incomplete.

scholarly journals A Functional Spatial Analysis Platform for Discovery of Immunological Interactions Predictive of Low-Grade to High-Grade Transition of Pancreatic Intraductal Papillary Mucinous Neoplasms

2018 ◽  
Vol 17 ◽  
pp. 117693511878288 ◽  
Author(s):  
Souptik Barua ◽  
Luisa Solis ◽  
Edwin Roger Parra ◽  
Naohiro Uraoka ◽  
Mei Jiang ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Subsequent Development ◽  
Ductal Adenocarcinoma ◽  
Low Grade ◽  
High Grade ◽  
Cellular Interactions ◽  
Spatial Interactions ◽  
Intraductal Papillary Mucinous Neoplasms ◽  
Remnant Pancreas ◽  
Mucinous Neoplasms

Intraductal papillary mucinous neoplasms (IPMNs), critical precursors of the devastating tumor pancreatic ductal adenocarcinoma (PDAC), are poorly understood in the pancreatic cancer community. Researchers have shown that IPMN patients with high-grade dysplasia have a greater risk of subsequent development of PDAC in the remnant pancreas than do patients with low-grade dysplasia. In this study, we built a computational prediction model that encapsulates the spatial cellular interactions in IPMNs that play key roles in the transformation of low-grade IPMN cysts to high-grade cysts en route to PDAC. Using multiplex immunofluorescent images of IPMN cysts, we adopted algorithms from spatial statistics and functional data analysis to create metrics that summarize the spatial interactions in IPMNs. We showed that an ensemble of models learned using these spatial metrics can robustly predict, with high accuracy, (1) the dysplasia grade (low vs high grade) and (2) the risk of a low-grade cyst progressing to a high-grade cyst. We obtained high classification accuracies on both tasks, with areas under the curve of 0.81 (95% confidence interval: 0.71-0.9) for task 1 and 0.81 (95% confidence interval: 0.7-0.94) for task 2. To the best of our knowledge, this is the first application of an ensemble machine learning approach for discovering critical cellular spatial interactions in IPMNs using imaging data. We envision that our work can be used as a risk assessment tool for patients diagnosed with IPMNs and facilitate greater understanding and investigation of the cellular interactions that cause transition of IPMNs to PDAC.

Basement–cover relationships in the East Greenland Caledonides: evidence from the Eleonore Bay Supergroup at Ardencaple Fjord

1993 ◽  
Vol 84 (2) ◽  
pp. 103-115 ◽  
Author(s):  
N. J. Soper ◽  
A. K. Higgins
Keyword(s):  
Shear Zones ◽  
Low Grade ◽  
East Greenland ◽  
Early Proterozoic ◽  
Basement Rocks ◽  
Erosion Level ◽  
Isotopic Studies ◽  
Extensional Faulting ◽  
Proterozoic Basement ◽  
Shed Light

AbstractThe Eleonore Bay Supergroup (EBG) is a 16 km-thick shallow-water sequence of Neoproterozoic age that is preserved within the East Greenland Caledonides in several tracts, surrounded by crystalline gneisses and schistose supracrustal rocks. The apparent downward transition from non-metamorphic EBG into gneiss gave rise to the classic ‘stockwerke’ hypothesis, in which all the metamorphism was regarded as Caledonian, and differences in grade were ascribed to the ascent of a migmatite front to different levels within the orogen. Field and isotopic studies in the 1970s however revealed that the underlying gneisses and schists had undergone orogenic reworking in mid-Proterozoic time; the EBG–basement contact was then interpreted as an approximately bedding-parallel décollement with apparent lag geometry, that is with EBG cover rocks in its hangingwall.Recent work in the northernmost EBG tract, at Ardencaple Fjord, has shed light on the problems posed by the basal relationships of the EBG, and together with regional structural and stratigraphic data leads to the following interpretation. There are two regionally important basement-cover interfaces within the East Greenland Caledonides. The earlier one is between Archaean/early Proterozoic gneisses and early Proterozoic supracrustal rocks, which were pervasively deformed in mid-Proterozoic time and form the basement to the Neoproterozoic Eleonore Bay cover sequence. This was deposited on a vast, continually subsiding shelf that is now preserved in East and NE Greenland and Svalbard, and contains Grenville detritus. EBG deposition was terminated by major extensional faulting of Vendian age; the succeeding Tillite Group is interpreted as a syn-rift sequence, presumably associated with the opening of Iapetus.The EBG–basement contacts that are not late faults are inferred to be extensional shear zones of Vendian age. These were reactivated in compression during the Caledonian orogeny in the Silurian, with metamorphic and fabric convergence, which accounts for the apparent downward transition from sedimentary rocks through schists into gneisses. Caledonian shortening was not large; inversion of the Vendian grabens was incomplete, so that the marginal shear zones retained their lag geometry and large tracts of low grade Eleonore Bay sediments are preserved at the present erosion level, surrounded by Proterozoic basement rocks, within the Caledonian belt of East Greenland.

scholarly journals Occurrence of Eutrichocheles modestus (Herbst) in the Near-shore Waters of Porto Novo, South India

Nature ◽  
1961 ◽  
Vol 191 (4790) ◽  
pp. 830-830 ◽  
Author(s):  
K. BALASUBRAHMANYAN ◽  
J. JACOB
Keyword(s):  
South India ◽  
Near Shore ◽  
Porto Novo

Superimposed low-grade metamorphism in the Mount Fisher area, southeastern British Columbia—implications for the East Kootenay orogeny

1982 ◽  
Vol 19 (3) ◽  
pp. 476-489 ◽  
Author(s):  
M. E. McMechan ◽  
R. A. Price
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Rocky Mountains ◽  
Regional Metamorphism ◽  
Low Grade ◽  
Canadian Cordillera ◽  
Windermere Supergroup ◽  
Granitic Intrusion ◽  
Block Faulting ◽  
Middle Proterozoic

Middle Proterozoic (~1500–1350 Ma) Belt–Purcell strata exposed in the Purcell and southwestern Rocky Mountains were affected by at least three distinct episodes of deformation and regional metamorphism. The oldest episode (1300–1350 Ma) apparently terminated Belt–Purcell sedimentation and involved folding, regional metamorphism, and granitic intrusion. The second episode (800–900 Ma) occurred during deposition of the Windermere Supergroup and involved uplift, block faulting, and low-grade regional metamorphism. Mesozoic–Cenozoic metamorphism, deformation, and plutonism overprinted the results of the earlier deformation and metamorphism.Illite crystallinity and muscovite polymorph ratios indicate that Purcell strata in the Mount Fisher area are in the lower green-schist to prehnite–pumpellyite facies of regional metamorphism. In the Steeples and Fisher blocks this metamorphism is related to structures that formed during the Late Cretaceous – Paleocene deformation. However, in the Sand Creek block the regional metamorphism is related to the development of a spaced cleavage that is folded by a Late Cretaceous – Paleocene nappe. Regional considerations suggest that this cleavage formed during the 1300–1350 Ma episode of deformation and metamorphism.The "East Kootenay orogeny" as currently defined embraces the two older episodes of tectonism. It is proposed that the term East Kootenay orogeny be restricted to designate the 1300–1350 Ma episode and that the term "Goat River orogeny" designate the 800–900 Ma episode of tectonism. The East Kootenay and Goat River orogenies appear to be correlative with the Racklan and Hayhook orogenies recognized in the northern Canadian Cordillera.

scholarly journals The provenance signal of climate–tectonic interactions in the evolving St. Elias orogen: framework component analysis and pyroxene and epidote single grain geochemistry of sediments from IODP 341 sites U1417 and U1418

2021 ◽  
Author(s):  
Barbara Huber ◽  
Heinrich Bahlburg
Keyword(s):  
Gulf Of Alaska ◽  
Low Grade ◽  
Thrust Belt ◽  
Rock Fragments ◽  
Source To Sink ◽  
Fold And Thrust Belt ◽  
Proximal Site ◽  
Near Shore ◽  
Single Grain ◽  
The Impact

AbstractThe St. Elias orogen and the Surveyor Fan in the adjacent Gulf of Alaska are a coupled source to sink system recording the interplay of tectonics and variable degrees of glaciation during the collision of the Yakutat terrane with the southern Alaska margin since the Miocene. The Miocene to Holocene sediments of the Surveyor Fan were drilled during IODP expedition 341. The recovered material is used to constrain information on changes in erosion centers during the last 10 Ma to study the impact of climatic and tectonic processes on orogen evolution. Point counting of sand- and silt-sized light framework components and geochemical single grain analysis of heavy mineral groups epidote and pyroxene is applied to analyze patterns of sedimentary provenance of two sites on the distal and proximal Surveyor Fan (Site U1417 and U1418, respectively). The studied sands and silts of Miocene to Pleistocene age are slightly enriched in feldspar (plag >> kf) at the proximal site, compositions at both sites do not show systematical changes with time of deposition. Framework component spectra uniformly reflect the expected active margin provenance. Epidote and pyroxene compositions are very consistent and show no change with time of deposition. Associations of epidote and pyroxene with albite, titanite and pumpellyite are in line with near-shore sources in the Chugach Metamorphic Complex and the metabasite belt at its southern border, and in units of recycled detritus exposed in the fold and thrust belt on the western Yakutat Terrane, respectively. Rock fragments indicate input from mainly metamorphic sources during the Miocene and Pliocene and an increase of input from low-grade metamorphic and sedimentary rocks in the Pleistocene, a finding also indicated by the abundance of epidote and pyroxene. This implies increasing erosion of the near-shore areas of the fold and thrust belt with advance of glaciers to the shore since the Miocene, being enhanced by the onset of the Northern Hemisphere glaciation at the beginning of the Pleistocene. Climate changes connected to the mid-Pleistocene transition did not result in appreciable changes in the petrographic compositions. Glaciers seem to have remained nested in their topographically predefined positions, continuously feeding material with uniform characteristics into the fan.

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