New geophysical data from the northern Cordillera: preliminary interpretations and implications for the tectonics and deep geology

1994 ◽  
Vol 31 (6) ◽  
pp. 891-904 ◽  
Author(s):  
C. Lowe ◽  
R. B. Horner ◽  
J. K. Mortensen ◽  
S. T. Johnston ◽  
C. F. Roots
Keyword(s):  
Gravity Data ◽  
Field Studies ◽  
Geophysical Data ◽  
Fault System ◽  
Tectonic Activity ◽  
Denali Fault ◽  
The North ◽  
The Pacific ◽  
Proterozoic Basement ◽  
Seismic Sections

In this paper we analyze recently acquired geophysical data from the northern Cordillera and their relation to the mapped geology. A prominent gravity high (> −45 mGal (1 Gal = 1 cm/s2)) coincides with a magnetic low and an aseismic region in west-central Yukon where the underlying geology is dominated by quartzo-feldspathic rocks having moderate densities. Extension (~15%), magmatic underplating, and accretion of the anomalous region onto oceanic crust are three possible explanations.Magnetic, gravity, and seismicity data all show significant differences in the physical state of the crust on either side of the Tintina Fault and, together with geological data indicating large offset, suggest it was once a major crustal-scale strike-slip fault. The new gravity data also delineate an arcuate zone of steep gradients (up to 1.4 mGal/km) in the miogeocline, which may correlate with a west-dipping Proterozoic basement ramp mapped on deep seismic sections farther to the north and a transition from thin (east) to thick sediment cover (west). Seismicity data show that current tectonic activity is concentrated along the Pacific – North America plate margin in southwestern Yukon and adjacent Alaska and, although there is a marked decrease in activity inland of this margin, notable concentrations occur along the Denali Fault System and in the eastern miogeocline. There is a distinct absence of earthquakes in parts of the Selwyn Basin and in the northern Yukon–Tanana Terrane. Limited field studies suggest activity is confined to the upper 10–15 km of the crust.

scholarly journals THE INTRAPLATE VOLCANO-TECTONIC ACTIVITY IN NORTH-EASTERN AND SOUTH SECTORS OF THE PACIFIC LITHOSPHERIC PLATES WITH THE CONNECTION OF THE CHANGE OF ITS RELATIVE MOTION

2021 ◽  
Vol 49 (4) ◽  
pp. 102-127
Author(s):  
E. G. Mirlin ◽  
T. I. Lygina ◽  
E. I. Chesalova
Keyword(s):  
Relative Motion ◽  
Sedimentary Cover ◽  
Oceanic Lithosphere ◽  
Pacific Plate ◽  
Fault System ◽  
Tectonic Activity ◽  
The North ◽  
The Pacific ◽  
North Eastern ◽  
Absolute Age

The analysis of altimetric data in combination with bathymetry and gravimetry materials in the north-eastern and southern sectors of the Pacific Ocean, as well as detailed data on the underwater relief, the structure of the sedimentary cover, the composition and absolute age of basalts obtained within the area of domestic geological exploration for ferromanganese nodules (the Clarion-Clipperton zone) is carried out. Structural trends formed by local cone-shaped local structures of presumably volcanic nature, grouped along transform faults belonging to various stages of the kinematics of the Pacific Plate, have been traced in the structure of the oceanic lithosphere at various scale levels. The first trend corresponds to the extension of the fault system corresponding to the spreading system on the crest of the East Pacific rise before the restructuring of its planned geometry in the Paleocene-Eocene, the second coincides with their extension after the change in the relative movement of the Pacific Plate. The trends are characterized by planned disagreement, and an increase in the number of seamounts is observed in the areas of their intersection. Within the area of detailed studies, obvious signs of volcanic-tectonic activity were revealed: high dissection of the underwater relief, hills of different heights with steep slopes, whose volcanic nature is confirmed by differentiated basalts raised from their slopes, the absolute age of which indicates the multistage outpourings that occurred in an intraplate environment. The angular velocity of rotation of the spreading axis and the linear velocity of its advance with changes in the kinematics of the Pacific plate are estimated and possible reasons for changes in its relative motion are considered. An improved scheme of adaptation of the spreading zone to a change in the direction of relative plate movement is proposed, acc0ording to which an essential factor of intraplate volcanic-tectonic activity is the relaxation of stresses in the plate caused by external influence on it.

scholarly journals The 102–103° E geodivider in the modern lithosphere structure of Сentral Asia

2018 ◽  
Vol 9 (3) ◽  
pp. 989-1006 ◽  
Author(s):  
Yu. G. Gatinsky ◽  
T. V. Prokhorova ◽  
D. V. Rundquist
Keyword(s):  
Seismic Energy ◽  
The North ◽  
Large Structures ◽  
Central Asian ◽  
The Pacific ◽  
Three Rivers Region ◽  
Seismic Sections ◽  
Three Rivers ◽  
Crust Thickness ◽  
Metallogenic Characteristics

A quasi-linear zone of noticeable geological and geophysical changes, which coincides approximately with 102–103° E meridians, is termed by the authors as “geodivider”. Active submeridional faults are observed predominantly along the zone and coincide with its strike. Seismicity is most intensive in the central part of this zone, from the Lake Baikal to the Three Rivers Region at the Sino-Myanmar frontier. Transects with deep seismic sections and energy dissipation graphs show most sharply increasing seismic energy amounts and hypocenter depths in the western part of the geodivider which delimits (in the first approximation) the Central Asian and East Asian transitional zones between the North Eurasian, Indian and Pacific lithosphere plates. The transpression tectonic regime dominates west of the geodivider under the influence of the Hindustan Indentor pressure, and the transtension regime prevails east of it due to the Pacific subduction slab submergence and continuation. The regime change coincides with an abrupt increase in the crust thickness – from 35–40 km to 45–70 km – west of the geodivider, as reflected in the geophysical fields and metallogenic characteristics of the crust. The direction ofP- andS-waves anisotropy together with the GPS data show decoupling layers of the crust and mantle in the southern part of the geodivider. According to our investigations, the 102–103° E geodivider is a regional geological-geophysical border that may be compared with the Tornquist Line, and, by its scale, with the Uralian and Appalachian fronts and some others large structures.

scholarly journals Angular Unconformity of the Late Quaternary Strata in the Hetao Basin, North of the Ordos Block (West China): Timing and Its Tectonic Implications

2021 ◽  
Vol 9 ◽  
Author(s):  
Luanxi Bai ◽  
Xiwei Xu ◽  
Hao Luo ◽  
Kang Li ◽  
Xibin Tan ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Lacustrine Sediments ◽  
Tibet Plateau ◽  
Tectonic Activity ◽  
West China ◽  
The North ◽  
Ordos Block ◽  
The Pacific ◽  
Long Time ◽  
Lacustrine Facies

Following the uplift of the Tibet Plateau and the continuous subduction of the Pacific Plate, graben faulting began to appear around the Ordos Block in the Cenozoic. The Hetao Basin is a Cenozoic rift basin between the Ordos Block and the Yinshan Mountains, and Late Quaternary sedimentary strata, which have lacustrine facies, are widely distributed inside this basin. However, the evolution of the Hetao Basin and its related fault systems has been debated for a long time due to the lack of tectonic evidence. In this study, four sections named Haolaigou, Bianqianghao, Huhesala, and Hazigai are selected along the north margin of the Hetao Basin. With the lithology and structural analysis of the Upper Pleistocene series in these sections, two new angular unconformities are found within the 10 m thick sedimentary sequence of the lacustrine sediments. Based on the dating results, we speculate that these two upper and lower angular unconformities are formed between 33 ka BP and 40 ka BP, and 60 ka BP and 80 ka BP, respectively. The angular unconformities also provide tectonic constraints for the latest and ongoing tectonic activity in the Quaternary. This tectonic movement begins at around 80 ka BP and causes two different unconformities of the lower strata with varying degrees of deformation (tilt) but also leads to the final death of the ancient lake.

scholarly journals Structural Interpretation of the Qingdong Area in Bohai Bay Basin from Shipborne Gravity Data

2015 ◽  
Vol 22 (s1) ◽  
pp. 100-105
Author(s):  
Chunguan Zhang ◽  
Jingguo Chen ◽  
Mingyi Song ◽  
Jinkuan Wang ◽  
Bingqiang Yuan
Keyword(s):  
Gravity Data ◽  
Fault System ◽  
Bohai Bay ◽  
Rift Basin ◽  
Bohai Bay Basin ◽  
Local Structures ◽  
The North ◽  
Dongying Depression ◽  
Geological Implications ◽  
Tectonic Features

Abstract The Qingdong area, located in Bohai bay basin, was suspected good exploration prospects. In order to study tectonic features and find out favourable petroleum prospects in the area, the gravity data at a scale of 1:50,000 were interpreted. This paper, through data processing and synthetic interpretation of the high-precision gravity data in the area, discusses characteristics of the gravity field and their geological implications, determines the fault system, analyses features of the main strata, divides structure units and predicts favourable petroleum zones. The results showed that the faults controlled the development of the Mesozoic and Cenozoic strata and the distribution of local structures in this area. The study revealed that the Qingtuozi uplift and the Kendong uplift in the north were formed in Mesozoic, and the Qingdong depression in the middle was the rift basin in Mesozoic and Cenozoic. Thicker strata in Mesozoic and Cenozoic developed in the Dongying depression and the Qingdong depression, so there is abundant hydrocarbon in these two depressions, and then the Guangligang rise-in-sag and the Qingdong rise-in-sag developed in the center in these two depressions are also favorable places for prospecting

Tectonic Controls on Cenozoic Sedimentation in the North Island New Zealand

1988 ◽  
Vol 6 (2) ◽  
pp. 104-117
Author(s):  
K.B. Spörli
Keyword(s):  
East Coast ◽  
Fault System ◽  
Clockwise Rotation ◽  
The North ◽  
Alpine Fault ◽  
The Pacific ◽  
Pacific Side ◽  
Forearc Basins ◽  
Subduction System ◽  
Coast Region

Cenozoic deformation of the North Island was dominated by the “closure” of the Challenger Rift and the establishment of the presently active subduction system. The initiation of subduction-related volcanic chains and their subsequent migration influenced the source of clastic material deposited in the Neogene basins. Uplift patterns, shoreline and drainage configurations were governed by complex 3-D distortion of the transition between the Alpine Fault system in the south and the Hikurangi through subduction system in the north. Along the Pacific side of the island, in Northland, some “piggy back” basins were formed on allochthonous pockets of sediments involved in obduction of ocean floor rocks onto the North island. Clockwise rotation on the east coast region and alternate coupling and decoupling across the subduction thrust created short-lived forearc basins. Axial ranges, and derivation of gravels from them are younger than 1 m y B.P. A very young, still active cross structure due to oblique subduction led to the formation of South Taranaki Bight, caused differences in the width of the axial ranges along their length and may be the reason for the peculiar coastal indentation of Hawke Bay.

scholarly journals Potential-field modelling of the prospective Chibougamau area (northeastern Abitibi subprovince, Quebec, Canada) using geological, geophysical, and petrophysical constraints

2020 ◽  
pp. 1-16
Author(s):  
Amir Maleki ◽  
Richard Smith ◽  
Esmaeil Eshaghi ◽  
Lucie Mathieu ◽  
David Snyder ◽  
...  
Keyword(s):  
Potential Field ◽  
Gravity Data ◽  
Geophysical Data ◽  
Magnetic Data ◽  
Data Sets ◽  
Seismic Section ◽  
Potential Field Data ◽  
Abitibi Subprovince ◽  
Seismic Sections ◽  
Potential Field Modelling

This paper focusses on obtaining a better understanding of the subsurface geology of the Chibougamau area, in the northeast of the Abitibi greenstone belt (Superior craton), using geophysical data collected along a 128 km long traverse with a rough southwest–northeast orientation. We have constructed two-dimensional (2D) models of the study area that are consistent with newly collected gravity data and high-resolution magnetic data sets. The initial models were constrained at depth by an interpretation of a new seismic section and at surface by the bedrock geology and known geometry of lithological units. The attributes of the model were constrained using petrophysical measurements so that the final model is compatible with all available geological and geophysical data. The potential-field data modelling resolved the geometry of plutons and magnetic bodies that are transparent on seismic sections. The new model is consistent with the known structural geology, such as open folding, and provides an improvement in estimating the size, shape, and depth of the Barlow and Chibougamau plutons. The Chibougamau pluton is known to be associated with Cu–Au magmatic-hydrothermal mineralisation and, as the volume and geometry of intrusive bodies is paramount to the exploration of such mineralisation, the modelling presented here provides a scientific foundation to exploration models focused on such mineralisation.

Stratigraphy, palynology, and provenance of the Colorado Creek basin, Alaska, USA: Oligocene transpressional tectonics along the central Denali fault system

2004 ◽  
Vol 41 (4) ◽  
pp. 457-480 ◽  
Author(s):  
Jeffrey M Trop ◽  
Kenneth D Ridgway ◽  
Arthur R Sweet
Keyword(s):  
Compositional Data ◽  
Middle Eocene ◽  
Volcanic Eruptions ◽  
Fault System ◽  
Thrust Faults ◽  
South Side ◽  
Denali Fault ◽  
The North ◽  
Early Oligocene ◽  
Middle Unit

New sedimentologic, biostratigraphic, and compositional data from a 415-m-thick section of siliciclastic and volcanic strata document Oligocene synthrusting sedimentation south of the McKinley segment of the Denali fault system. Strata of the Colorado Creek basin are presently exposed on the south side of the central Alaska Range in the footwalls of north-dipping thrust faults. New measured sections define a three-part stratigraphy. Lowermost strata consist of a ~30-m-thick unit of marine sandstone and mudstone that contain Late Cretaceous dinoflagellate taxa. The middle unit consists of ~330 m of conglomerate, sandstone, and mudstone interpreted as braided stream and floodplain deposits. This middle unit contains early Oligocene pollen and spore assemblages. The upper unit is 55 m thick and contains lava flows, tuff, and pumice interpreted as the product of subaerial volcanic eruptions. Direct age data are lacking from the upper unit. Compositional data from the middle unit indicate that detritus was derived from sedimentary and igneous source terranes exposed on both the north and south side of the McKinley fault. Matching source lithologies north of the McKinley fault with conglomerate clast types in the Colorado Creek basin implies 30–33 km of maximum post-early Oligocene dextral displacement along the fault. We interpret the Oligocene strata of the Colorado Creek basin as a product of transpressional deformation that produced north-dipping thrust faults associated with strike-slip displacement on the central Denali fault. Our data from the Colorado Creek basin, in combination with previous studies, document a major episode of middle Eocene – late Oligocene synorogenic sedimentation along the Denali fault from British Columbia to southwestern Alaska.

scholarly journals Development of Crustal-Scale Shear Zones at the Singhbhum Craton–Eastern Ghats Belt Boundary Region: A Critical Review of the Mesoarchean–Neoproterozoic Odyssey

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 6) ◽  
Author(s):  
Gautam Ghosh ◽  
Proloy Ganguly ◽  
Shuvankar Karmakar ◽  
Sankar Bose ◽  
Joydip Mukhopadhyay ◽  
...  
Keyword(s):  
Shear Zones ◽  
Boundary Region ◽  
Eastern Ghats ◽  
Fault System ◽  
Tectonic Activity ◽  
Eastern Ghats Belt ◽  
Singhbhum Craton ◽  
The North ◽  
Suprasubduction Zone ◽  
Scale Shear

Abstract A number of crustal-scale shear zones have developed along the southern margin of the Singhbhum Craton, in the boundary with the Neoarchean Rengali Province and the Meso-Neoproterozoic Eastern Ghats Belt. The cratonic part, evolved in a suprasubduction zone setting, bears imprints of late Mesoarchean orogenic episode (D1C) at ca. 3.1 Ga with folding and thrust imbrication of the cratonic rocks. The succeeding orogenic imprint is etched in the Neoarchean (~2.8 Ga) with development of the Sukinda thrust along the craton margin and thrust-related deformation of the rocks of the Rengali Province (D2C-D1R). The latter event remobilized cratonic fringe with development of a spectacular E-W trending transpressional belt in the Southern Iron Ore Group rocks cored by the Sukinda ultramafics. In the Eastern Ghats Belt, the major ultrahigh-temperature orogeny took place during the Grenvillian-age (~1.0-0.9 Ga) assembly of the supercontinent Rodinia. This belt eventually got juxtaposed against the expanded Singhbhum Craton in the end-Neoproterozoic time (~0.5 Ga) along the Kerajang Fault Zone. This latter event remobilized a large part of the Rengali Province (D2R) with development of an intraterrane transpressional belt bounded by the Barkot Shear Zone in the north. The northern fringe of the intruding Eastern Ghats Belt developed a complex network of strike-slip fault system under this impact, probably an outcome of tectonic activity along the Kuunga suture, which signifies the joining of greater India with East Antarctica. The present synthesis visualizes early development in the craton through formation of a typical orogenic sequence, imbricated in thrust piles, resulting from a ca. 3.1 Ga orogeny. Further cratonic expansion was achieved via repetitive accretion and remobilization, development of crustal-scale faults and transpressional belts at ca. 2.8 Ga and ca. 0.5 Ga, much in a similar fashion as documented along oblique convergent margins of all ages.

Observations of uplift and subsidence along the North American Pacific coast – illuminating the geodynamic complexity of an active margin

2021 ◽  
Author(s):  
Maryam Yousefi ◽  
Glenn Milne ◽  
Shaoyang Li ◽  
Kelin Wang ◽  
Alan Bartholet ◽  
...  
Keyword(s):  
North American ◽  
Pacific Coast ◽  
Ice Sheets ◽  
Fault System ◽  
Tectonic Activity ◽  
Cascadia Subduction Zone ◽  
Plate Boundaries ◽  
Mountain Glacier ◽  
The North ◽  
Vertical Land Motion

<p>The Pacific Coast of Central North America is a geodynamically complex region subject to various geophysical processes with different patterns of vertical land motion. It includes two distinct tectonic regimes: the Cascadia subduction zone and the strike-slip San Andreas fault system. The vertical land motion in this region reflects not only tectonic activity of these plate boundaries, but also isostatic signals associated with different loading effects such as the (de)glaciation of North American ice sheets and the more contemporary, anthropogenically-related groundwater extraction and mountain glacier mass loss. These processes occur over a broad range of timescales and are observed by a variety of measuring techniques.</p><p>Here we combine geological measurements of relative sea level (RSL) change with contemporary observations of vertical land motion inferred from geodetic data to decipher and thus better understand the contribution from various individual processes. Our results suggest that contemporary vertical land motion is dominated by Cascadia interseismic deformation and the isostatic response to the retreat of the North American ice sheets but is also influenced by other contemporary processes. We present some model results that illustrate the contributions of the above-mentioned processes to RSL projections along this coastline.  </p>

scholarly journals Lithostratigraphy of the Red Sea Region

GeoArabia ◽  
2005 ◽  
Vol 10 (3) ◽  
pp. 49-126 ◽  
Author(s):  
Geraint Wyn ap Gwilym Hughes ◽  
Robert S. Johnson
Keyword(s):  
Red Sea ◽  
Middle Miocene ◽  
Field Studies ◽  
Early Miocene ◽  
Lower Miocene ◽  
The North ◽  
Lithostratigraphic Units ◽  
Marine Carbonates ◽  
Sedimentary Succession ◽  
Proterozoic Basement

ABSTRACT The onshore and offshore Saudi Arabian Red Sea region contains a series of lithostratigraphic units that have not previously been formally defined and described. Based on an intensive study of the succession, a lithostratigraphic scheme is proposed in a lexicon format that integrates biostratigraphic, sedimentological, seismic and field studies from the Midyan Peninsula in the north, to the Jizan Coastal Plain in the south. In view of the economic aspect of the Neogene succession and greater accessibility to Neogene subsurface samples, emphasis has been placed on a revision of the Neogene lithostratigraphy. Resting upon Proterozoic Basement, the sedimentary succession was deposited during the Cretaceous to Pleistocene times. The oldest pre-rift Suqah Group nonconformably overlies the Proterozoic Basement and consists of Upper Cretaceous shales of the Adaffa Formation and Cretaceous to Palaeogene sandstones, shales and thin limestones of the Usfan Formation. A series of volcanics includes the early to middle Oligocene Matiyah Formation and the late Oligocene-early Miocene Jizan Group. The Neogene succession displays a great lithological diversity. The Tayran Group (Al Wajh, Musayr and Yanbu Formations) includes marginal marine siliciclastics of the Al Wajh Formation, and represents the earliest rift-associated sediments deposited during the earliest Miocene. These are conformably overlain by lower Miocene shallow-marine carbonates of the Musayr Formation. In some of the central Red Sea onshore basins, thick lower Miocene submarine evaporites of the Yanbu Formation were deposited under locally restricted conditions and form the third formation of the Tayran Group. Rapid subsidence during the early Miocene caused deposition of deep-marine, planktonic-foraminiferal mudstones and thick submarine fan sandstones of the Burqan Formation. Carbonates, marine mudstones and submarine evaporites of the Maqna Group (Jabal Kibrit and Kial Formations) unconformably overlie the Burqan Formation and were deposited during latest early Miocene to earliest middle Miocene. The Jabal Kibrit Formation consists of an anhydrite-carbonate facies, of which the carbonates form the Wadi Waqb Member. Siliciclastic facies of the Jabal Kibrit Formation are termed the Umm Luj Member. Above the Jabal Kibrit Formation, the Kial Formation is typified by interbedded anhydrites, calcareous siltstones and carbonates, and includes the Sidr, Nakhlah, Yuba, Rayaman and Sabya Members. Within the region, thick evaporites of the Mansiyah Formation were deposited extensively during the middle Miocene, and are overlain by poorly exposed sands, shales and thin anhydrite beds of the middle to upper Miocene Ghawwas Formation. The Lisan Group unconformably overlies the Ghawwas Formation and consists of coarse alluvial sands and gravels of possible Pliocene to Holocene age.

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