On the kinematics and timing of Rodinia breakup: a possible rift–transform junction of Cryogenian age at the southwest cape of Congo Craton (northwest Namibia)

2021 ◽  
Author(s):  
P.F. Hoffman
Keyword(s):  
Rift Zone ◽  
Carbonate Platform ◽  
The West ◽  
Growth Fault ◽  
Tilt Correction ◽  
Northern Zone ◽  
Kaoko Belt ◽  
Transform Zone ◽  
Splay Fault ◽  
Normal Sense

Abstract After tilt correction for Ediacaran thick-skinned folding, a pair of Cryogenian half grabens at the autochthonous southwest cape of Congo Craton (CC) in northwest Namibia restore to different orientations. Toekoms sub-basin trended east-northeast, parallel to Northern Zone (NZ) of Damara belt, and was bounded by a normal-sense growth fault (2 290 m throw) dipping 57° toward CC. Soutput sub-basin trended northwest, oblique to NZ and to north-northwest-trending Kaoko Belt. It was bounded by a growth fault (750 m down-dip throw) dipping steeply (~75°) toward CC. Soutput growth fault could be an oblique (splay) fault connecting a Cryogenian rift zone in NZ with a sinistral transform zone in Kaoko Belt. A transform origin for the Kaoko margin accords with its magma-poor abrupt shelf-to-basin change implying mechanical strength, unlike the magma-rich southern margin where a gradual shelf-to-basin change implies a mechanically weak extended margin. A rift−transform junction is kinematically compatible with observed north-northwest−south-southeast Cryogenian crustal stretching within CC. Post-rift subsidence of the CC carbonate platform varies strongly across the south-facing but not the west-facing shelf. A sheared western CC margin differs from existing Kaoko Belt models that posit orthogonal opening with hyper-extended continental crust. Carbonate-dominated sedimentation over southwest CC implies palaeolatitudes ≤35° between 770 and 600 Ma.

scholarly journals Growth faults affecting depositional geometry, facies and sequence stratigraphy record on a carbonate platform edge (South Vercors Urgonian platform, SE France)

2019 ◽  
Vol 190 ◽  
pp. 1
Author(s):  
Serge Ferry ◽  
Danièle Grosheny
Keyword(s):  
Small Area ◽  
Carbonate Platform ◽  
Growth Fault ◽  
Sequence Stratigraphic ◽  
Fine Grained ◽  
Accommodation Space ◽  
Western Side ◽  
The Waves ◽  
Se France ◽  
Depositional Geometries

The first two calcarenite units at the base of the Urgonian limestones on the southern edge of the platform bear different depositional geometries depending on place (Cirque d’Archiane to Montagnette and Rocher de Combau). The lower calcarenite unit (Bi5 of Arnaud H. 1981. De la plate-forme urgonienne au bassin vocontien. Le Barrémo-Bédoulien des Alpes occidentales entre Isère et Buëch (Vercors méridional, Diois oriental et Dévoluy). Géologie Alpine, Grenoble, Mémoire 12: 3. Disponible sur https://tel.archives-ouvertes.fr/tel-00662966/document), is up to 200 m thick and shows three different patterns, in terms of accommodation space, from the western Archiane Cirque to the Montagnette to the east. On the western side of the Cirque, the unit begins on slope fine-grained limestone with thin sigmoïdal offlap geometry, suggesting little available space after a relative sea level fall. It is overlain by thick progradational/aggradational, then purely aggradational calcarenite capped by a coral and rudist-bearing bed. This bed is, therefore, interpreted as a maximum (although moderate) flooding facies. The depositional geometry is different on the eastern side of the Cirque, where a progradational pattern in the lower part of the unit is interrupted by a rotational movement affecting the depositional profile. The deformation promoted aggradation updip and retrogradation downdip as a result of starvation. The inferred growth fault updip (thought to be responsible for the change) began to function earlier at the Montagnette, explaining the huge calcarenite clinoforms found there, filling a deeper saddle created in the depositional profile. The same fault probably was reactivated later during the deposition of the overlying, thinner Bi6-1 unit, which appears at Rocher de Combau with an uncommon tidal facies at the base. A rotational bulge, created by the inferred growth fault, would have protected a small area behind it to spare the local calcarenite deposition from the waves for a while. These two examples show that sequence stratigraphic interpretation may differ from one place to the other, and even show opposite trends due to this kind of disturbance.

Evolution of a deep-water carbonate platform: Upper Cretaceous to Pleistocene sedimentary environments on the west Florida margin

1991 ◽  
Vol 101 (1-4) ◽  
pp. 163-179 ◽  
Author(s):  
Anne F. Gardulski ◽  
Marguerite H. Gowen ◽  
Amy Milsark ◽  
Sandra D. Weiterman ◽  
Sherwood W. Wise ◽  
...  
Keyword(s):  
Deep Water ◽  
Upper Cretaceous ◽  
Carbonate Platform ◽  
The West ◽  
Sedimentary Environments ◽  
Water Carbonate

scholarly journals The closure of the Vardar ocean (the western domain of the northern Neotethys) from early Middle Jurassic to Paleocene time, based on surface geology of eastern Pelagonia and the Vardar zone, biostratigraphy, and seismic-tomographic images of the mantle below the Central Hellenides

2021 ◽  
Author(s):  
Rudolph Scherreiks ◽  
Marcelle Boudagher-Fadel
Keyword(s):  
Middle Jurassic ◽  
Carbonate Platform ◽  
Late Triassic ◽  
East Side ◽  
The West ◽  
Volcanic Arc ◽  
Tomographic Images ◽  
Passive Margins ◽  
Sedimentary Environments ◽  
Surface Geology

Seismic tomographic images of the mantle below the Hellenides indicate that the Vardar ocean probably had a composite width of over 3000 kilometres. From surface geology we know that this ocean was initially located between two passive margins: Pelagonian Adria in the west and Serbo-Macedonian-Eurasia in the east. Pelagonia was covered by a carbonate platform that accumulated, during Late Triassic to Early Cretaceous time, where highly diversified carbonate sedimentary environments evolved and reacted to the adjacent, converging Vardar ocean plate. We conceive that on the east side of the Vardar ocean, a Cretaceous carbonate platform evolved from Aptian to Maastrichtian time in the forearc basin of the Vardar supra-subduction volcanic arc complex. The closure of the Vardar ocean occurred in one episode of ophiolite obduction and in two episodes of intra-oceanic subduction.

scholarly journals Geological structure of the Pre-jurassic basement of the Yugansk-Koltogorsk zone of the West Siberia

LITOSFERA ◽  
2018 ◽  
pp. 839-858 ◽  
Author(s):  
Kirill S. Ivanov ◽  
Stepan V. Berzin ◽  
Nadezhda V. Vakhrusheva ◽  
Nikolai P. Kostrov ◽  
Olga E. Pogromskaya
Keyword(s):  
Inductively Coupled Plasma ◽  
Rift Zone ◽  
West Siberia ◽  
Geological Structure ◽  
The West ◽  
X Ray ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Geological Map ◽  
Rift Zones

Subject of the study.We have carried out an additional exploration on petrography, petrochemistry, geochemistry, geochronology and biostratigraphy of rock complexes of the Yugansk-Koltogorsk (central part of West Siberia).Materials and methods.The materials are core samples from wells that penetrated the Pre-Jurassic basement rock complexes The used methods are as follows: X-ray spectrum microanalysis (Cameca SX 100, JEOL-733 Superprobe); the silicate analysis of the rocks (СРМ-18 and EDX-100); mass-spectroscopy with inductively coupled plasma (ICP-MS) (ELAN-9000 and Element2); zircons were analysed with a high resolution ionic microprobe SHRIMP-II (U-Pb); Ar-Ar dating was carried out by Micromass 5400; biostratigraphy, petrochemestry.Results.A geological map of Yugan-Koltogor zone of the central part of West-Siberian plate in a scale 1:500 000 was created. The map is a set of informational geological, geophysical and other layers. It was established that age of granites is Early Permian, the basalts of the rift zone began to form 268.4 ± 7.5 Ma ago (Ar-Ar). Conclusions. Volcanism in the axial rift zones of the West-Siberian megabasin basement began earlier than it is supposed before our study and significantly earlier of that of trap basalts of Siberian platform.

scholarly journals Submarine Terraces reveal Late Quaternary Tectonic deformation in the Intermediate Zone between the Island Shelf and Rift Zone of the Middle Part of the Nanseishoto Islands, Southwest Japan

2021 ◽  
Author(s):  
Hideaki Goto
Keyword(s):  
Subduction Zone ◽  
Rift Zone ◽  
Late Quaternary ◽  
Middle Part ◽  
Tectonic Deformation ◽  
Southwest Japan ◽  
The West ◽  
West Side ◽  
Marine Terraces ◽  
Island Shelf

Abstract Late Quaternary tectonic deformation of coastal areas is usually examined based on the height distribution of paleo-shorelines observed on marine terraces. However, it is difficult to examine deformation along the subduction zone, in which small, isolated islands are distributed. In this paper, the author focuses on the widespread shallow submarine terraces surrounding the Iheya-Izena islands in the middle part of the Nanseishoto islands, Southwest Japan, where crustal deformation is not known. The islands are located in the intermediate zone between island shelf uplifted during the Late Quaternary and the rift zone occurred to the northwest, along the Okinawa trough. Detailed topographic anaglyph images and maps of the islands were produced using a digital elevation model (DEM) of the seafloor, which is stored by the Japan Coast Guard (JCG) and the Advanced Institute of Science and Technology (AIST). Topographic anaglyph images enabled us to identify the widespread distribution and deformation of the shallow seafloor above −200 m using red-cyan glasses. Four terrace-like features divided by small steps were found on the shallow seafloor, which are named T1, T2, T3, and T4, in descending order. Topographic expressions of paleo-shoreline depths are preserved on submarine terraces formed during the last glacial period. The paleo-shoreline depths of terraces T2 and T3 are −60 m and −70 m on the west side and −70 m and −80 m, respectively, on the east side of Iheyajima island; this indicates southeastward tilting. The tilting ratio of T2 and T3 was calculated to approximately 1‰. The tilting rate is approximately 1×10^4/kyr, assuming that the T2 was formed in 10–11 kyr. This is much more rapid than that of the last inter-glacial marine terraces in the Muroto peninsula of Shikoku, Japan, with a tilting rate of 4×10^5/kyr, which formed by steep northward tilting against the Nankai subduction zone. The author suggests that this phenomenon is not related to mega-thrusting along the subduction zone, but rather to local deformation, probably caused by the reverse faulting of nearby active submarine faults along the west side of the islands.

Mid-Paleozoic thrusting at the Appalachian deformation front: Port au Port Peninsula, western Newfoundland

1991 ◽  
Vol 28 (12) ◽  
pp. 1992-2002 ◽  
Author(s):  
John W. F. Waldron ◽  
Glen S. Stockmal
Keyword(s):  
Carbonate Platform ◽  
Foreland Basin ◽  
Late Ordovician ◽  
Western Boundary ◽  
Seismic Profiles ◽  
The West ◽  
Deformation Front ◽  
Middle Ordovician ◽  
Triangle Zone ◽  
Map Scale

Structures exposed on Port au Port Peninsula in western Newfoundland record the nature of the Appalachian deformation front, which forms the western boundary of the Humber tectono-stratigraphic zone. The major structures affect the Late Ordovician to Late Silurian Long Point – Clam Bank succession, but not the unconformably overlying Carboniferous rocks; they are probably of Devonian age.At the west coast of the peninsula, Long Point and Clam Bank strata are affected by both east-vergent and west-vergent structures. The basal surface of the succession is interpreted as an east-vergent thrust, forming the upper detachment of a "triangle zone," and correlates with a similarly located contact seen in offshore multichannel seismic profiles. Within the succession, east-vergent deformation zones locally duplicate the stratigraphy. West-vergent structures, including a map-scale overturned fold north of Round Head mountain, are probably younger.Farther south, Middle Ordovician foreland basin sediments are also affected by east-vergent thrusts, which have been variably rotated by west-vergent folds. In the underlying Cambrian–Ordovician platform carbonate succession, east-vergent thrusts duplicate the stratigraphy.These structures are related to telescoping of the carbonate platform and the overlying Humber Arm Allochthon during Devonian westward wedging of the structural triangle zone beneath the Long Point – Clam Bank succession. The platform succession must therefore be allochthonous, and the Humber Arm Allochthon has been transported to the west of its Late Ordovician position.

Lucan 1.683f.

1990 ◽  
Vol 40 (2) ◽  
pp. 578-579
Author(s):  
A. Hudson-Williams
Keyword(s):  
Close Association ◽  
Far East ◽  
Literal Meaning ◽  
The West ◽  
The Far East ◽  
The Mediterranean ◽  
Normal Sense

So a frenzied matron cries out to Phoebus as she rushes through an appalled Rome. In CQ 34 (1984), 454f. I pointed out that the words primos in ortus could not here bear their normal sense ‘to the far east’ (as taken by Duff, similarly Bourgery-Ponchont, and others), which in view of the next line would be geographically absurd, and, distraught as the lady was, even so highly improbable. I did, however, then think R. J. Getty right in taking the expression primos ortus as simply = ‘the east’, and adding ‘the epithet primos appears to be otiose’. But I now feel very doubtful about the epithet being viewed as otiose in order that the words may denote Egypt; quite different are the passages noted in OLD primus 6 ‘belonging to the rising sun, eastern’, as Stat. Silv. 1.4.73 ‘occidiias primasque domos’ in the cited Sen. Oed. 116 ‘miles… ausus Eois equitare campis / figere et mundo tua signa primo’ the literal meaning is no doubt ‘on the world's first edge’ (Miller, Loeb), but its development into ‘eastern’ is readily seen. Egypt, however, as viewed by Rome, is but the bare beginning of the east, and that is what primos must indicate above (note emphatic position): see OLD primus 10 b ‘the nearest part of, the entrance, threshold, or sim., of, noting e.g. Ov. Fast. 1.717 ‘horreat Aeneadas et primus et ultimus orbis’, Cic. Fam. 3.6.2. ‘te in prima prouincia uelle esse, ut quam primum decederes’. In a characteristic departure from their stock meaning Lucan's words primos in ortus must then mean ‘to the threshold of the east’, i.e. the delta of the Nile, as explained in the next line (684): contrast 7.360 primo gentes oriente = ‘the nations of the far east’ (Duff). For Egypt viewed as the beginning of the east, cf. Mela 1.9 ‘Asiae prima pars Aegyptus’, Plin. Nat. 5.47 ‘[Africae] adhaeret Asia, quam patere a Canopico ostio [Nili] ad Ponti ostium Timosthenes…tradidit’, Mart. Cap. 6.675 ‘Aegyptus… Asiae caput, 3 quae una ab ostio Canopi ad ostium Ponti habet… milia passuum’; cf. the close association of Egypt with the east in Virg. Aen. 8.687 ‘Aegyptum uiresque Orientis’. For the varied use of the word primus should be noted too Luc. 9.413f. ‘nee… plus litora Nili / quam Scythicus Tanais primis a Gadibus absunt’, ‘from Gades in the far west’ (Duff), ‘Gades the first place in the west’ (Haskins), i.e. the threshold of the Mediterranean.

scholarly journals Submarine terraces reveal Late Quaternary tectonic deformation in the intermediate zone between the island shelf and rift zone of the middle part of the Nanseishoto Islands, southwest Japan

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hideaki Goto
Keyword(s):  
Subduction Zone ◽  
Rift Zone ◽  
Late Quaternary ◽  
Middle Part ◽  
Tectonic Deformation ◽  
Southwest Japan ◽  
The West ◽  
West Side ◽  
Marine Terraces ◽  
Island Shelf

AbstractLate Quaternary tectonic deformation of coastal areas is usually examined based on the height distribution of paleo-shorelines observed on marine terraces. However, it is difficult to examine deformation along the subduction zone, in which small, isolated islands are distributed. In this paper, the author focuses on the widespread shallow submarine terraces surrounding the Iheya–Izena islands in the middle part of the Nanseishoto Islands, Southwest Japan, where crustal deformation is not known. The islands are located in the intermediate zone between island shelf uplifted during the Late Quaternary and the rift zone occurred to the northwest, along the Okinawa trough. Detailed topographic anaglyph images and maps of the islands were produced using a digital elevation model (DEM) of the seafloor, which is stored by the Japan Coast Guard (JCG) and the Advanced Institute of Science and Technology (AIST). Topographic anaglyph images enabled us to identify the widespread distribution and deformation of the shallow seafloor above − 200 m using red–cyan glasses. Four terrace-like features divided by small steps were found on the shallow seafloor, which are named T1, T2, T3, and T4, in descending order. Topographic expressions of paleo-shoreline depths are preserved on submarine terraces formed during the last glacial period. The paleo-shoreline depths of terraces T2 and T3 are − 60 m and − 70 m on the west side and − 70 m and − 80 m, respectively, on the east side of Iheyajima Island; this indicates southeastward tilting. The tilting ratio of T2 and T3 was calculated to approximately 1‰. The tilting rate is approximately 1 × 10–4/kyr, assuming that the T2 was formed in 10–11 kyr. This is much more rapid than that of the last inter-glacial marine terraces in the Muroto peninsula of Shikoku, Japan, with a tilting rate of 4 × 10–5/kyr, which formed by steep northward tilting against the Nankai subduction zone. The author suggests that this phenomenon is not related to mega-thrusting along the subduction zone, but rather to local deformation, probably caused by the reverse faulting of nearby active submarine faults along the west side of the islands.

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