scholarly journals Structural evolution of the northwestern Zagros, Kurdistan Region, Iraq: Implications on oil migration

GeoArabia ◽  
2012 ◽  
Vol 17 (2) ◽  
pp. 81-116 ◽  
Author(s):  
Csontos László ◽  
Sasvári Ágoston ◽  
Pocsai Tamás ◽  
Kósa László ◽  
Azad T. Salae ◽  
...  
Keyword(s):  
Structural Evolution ◽  
Geological Mapping ◽  
Kurdistan Region ◽  
Zagros Mountains ◽  
Lateral Shear ◽  
The North ◽  
Late Neogene ◽  
Tectonic Zones ◽  
Mountain Chain ◽  
Structural Boundary

ABSTRACT The studied area in Kurdistan Region of Iraq lies across an important topographic/structural boundary between the southern lowlands and the northern, folded and imbricated Zagros Mountains. It also encompasses a prominent change in structural orientation of the northern Zagros, from a general NW-SE “Zagros” to an E-W “Taurus” trend. Geological mapping and structural observations, both in the mountains (Mesozoic–Palaeogene) and in the lowlands (Neogene), led to the following conclusions. (1) The oldest recorded deformation is a layer-parallel shortening, coupled with southwest-vergent shear that was followed by major folding of ca. 10 km wavelength and ca. 1,000 m amplitude. Even the Upper Miocene–Pliocene Bakhtiari Formation has steep to overturned beds in some parts, and synclines preserve syn-tectonic strata of Neogene–Pliocene age. Box folding is associated with crestal collapse, internal thrusting in the core and with formation of systematic joint sets. (2) On the southern limb of the major folds, thrusting of variable offset can be observed. The thrusts on the southern and northern limbs are considered responsible for the major uplift during main folding. (3) En-échelon fold-relay patterns suggest left-lateral shear along the EW-oriented segment and right-lateral shear along the NW-oriented segment. (4) A quick-look qualitative analysis of striated fault planes suggests a variable shortening trend from NE-SW to N-S, and some rare NW-SE shortening all associated with thrust faults. (5) The general structural setting of the area is linked to the north-eastwards to northwards propagation of the Arabian Margin beneath Eurasia. The ca. 30° bend in the mountain chain may be explained by the original shape of the Arabian Margin, or by pre-existing tectonic zones of E-W orientation in the northern part. Several observations suggest that there was no oroclinal bending (i.e. major rotation) of different parts of the chain, but the structures simply molded on their local buttress (almost) according to present orientations. However, a limited amount of rigid-body rotation in the different segments cannot be ruled out. The changing shortening directions generated several structural combinations on both the NW-SE Zagros and the E-W Taurus segments of the arc, many of which are still preserved. (6) Spectacular bitumen seepage in Upper Cretaceous and Palaeocene limestone originates from fractures or geodes of these formations. Many of these bitumen-filled voids are linked to the above-described Late Neogene–Recent shortening-folding process; therefore hydrocarbon migration into these voids is interpreted to be very young. This contradicts earlier ideas about massive Late Cretaceous breaching and bleeding off of hydrocarbons in this region.

Slip-sense inversion in Iran: Implications for Eurasian tectonics

2020 ◽  
Author(s):  
Bernard Guest
Keyword(s):  
Structural Evolution ◽  
Sediment Supply ◽  
Process Models ◽  
Fault System ◽  
Free Boundaries ◽  
Iranian Plateau ◽  
Existing Structures ◽  
The North ◽  
Collision Zone ◽  
Late Neogene

<p>The left-lateral Doruneh Fault System (DFS) bounds the north margin of the Central Iranian microplate, and has played an important role in the structural evolution of the Turkish-Iranian Plateau and of Afghanistan. The western termination of the DFS is a sinistral synthetic branch fault array that shows clear kinematic evidence of having undergone recent slip sense inversion from a dextral array to a sinistral array in the latest Neogene or earliest Quaternary. Similarly, kinematic evidence from the Anarak Metamorphic complex at the southwestern most branch of the DFS terminal fault array suggests that this core complex formed at a transpressive left stepping termination and that it was inverted in the latest Neogene to a transtensional fault termination. The recognition that the DFS and possibly other faults in NE Iran were inverted from dextral to sinistral strike slip in the latest Neogene, and the likely connection between the DFS and the Herat Fault of Afghanistan suggests that the evolutions of Afghanistan and the Indo-Asian collisional system are linked to the tectonic evolution of the Turkish-Iranian Plateau. This speculative model explains the Late Neogene tectonic realignment of the Arabia-Eurasia collision zone in terms of the interaction between the Afghan blocks that were extruding west from the Indo-Asian collision and the Turkish Iranian collision zone that was evolving to the east as Arabia sutured diachronously with Eurasia. The collision of the Afghan blocks with East Iran effectively locked the respective eastern and western free boundaries for the Arabia-Eurasia, and Indo-Asian collisional belts and forced them to diverge away from one another.<span> If confirmed,</span> this explains the Late Miocene to Pliocene tectonic reorganization that is recognized across the Middle East and has implications for geologic process models across the region. Regional tectonic reorganization and/or inversion may (1) invert and possibly breach older Cenozoic structures while forming a younger generation of post-Miocene structures, (2) reorganize drainage and sediment supply networks, and sealing and obscuring older structural and stratigraphic bodies under younger sediments, (3) rejuvenate existing structures and trigger secondary fluid migration, and (4) increase exhumation, sediment supply, and subsidence in late Neogene basins across the region.</p>

Intense deformation of the caprock on salt extrusions in the Iranian Zagros Mountains – Insights from geological mapping and analogue modeling

2021 ◽  
Author(s):  
Prokop Závada ◽  
Jiří Bruthans ◽  
Sadegh Adineh ◽  
Michael Warsitzka ◽  
Mohammad Zare
Keyword(s):  
Structural Evolution ◽  
Confining Pressure ◽  
Field Studies ◽  
Geological Mapping ◽  
Parameter Study ◽  
Zagros Mountains ◽  
Fine Grained ◽  
Southern Iran ◽  
Fold And Thrust Belt ◽  
Ductile Shearing

<p>The Zagros fold-and-thrust belt in Southern Iran is famous for its spectacular outcrops of salt diapirs. Most of these diapirs already existed prior to the onset of the Zagros orogeny, but tectonic shortening caused their reactivation and extrusion of the salt. Thus, the diapir exposures often provide access to intense internal deformation of the Hormuz salt series and its entrained interlayers. However, highly soluble evaporites (mainly halite) were already dissolved in many of the exposures leaving behind degraded ‘caprock’, which is built of a multi-compositional residuum of less soluble minerals and rocks. Based on geological field studies on two iconic salt diapirs in Southern Iran, the Karmostaj (Gach) and the Siah Taq diapir, we ascertained that the caprock is also intensively deformed. The accessible part of the caprock is roughly 200 m thick and consists of a fine-grained, laminated gypsum containing fragments of brecciated carbonates and siliciclastics.  Especially in the down- and mid-slope regions of the salt exposure, this mixture is sheared and folded, but also dissected by thrust faults. Since such deformation processes in the caprock were not described before, there is a lack in explanations for the timing, the depth of formation and the structural evolution of these structures. For instance, it is unclear if the ductile shearing of the relatively competent gypsum matrix and the brecciation of the clasts took place near the surface or in larger depths (a few hundreds of meters), where confining pressure is higher.</p><p>In this study, we want to classify the observed structures in the caprock, characterize deformation mechanisms and differentiate typical deformation domains. Based on that, we speculate about the timing and structural evolution of the caprock deformation and suggest that three scenarios can be imagined: (1) Pre-extrusion deformation: The caprock exposed today was buried by a thicker caprock package and, therefore, is compacted and mechanically strong.  With the onset of the Zagros orogeny, tectonic shortening of the buried diapir caused lateral deformation before the salt extrusion. (2) Syn-extrusion deformation: The caprock is relatively young and was mechanically weak after its formation. Thus, it was deformed during diapir extrusion and, then, solidified during degradation of the salt. (3) Post-extrusion deformation: The caprock was mainly formed after salt extrusion, but it remained relatively immobile. The caprock matrix is occasionally weakened by the infiltration of meteoric water, and continued to be deformed due to gravitational gliding even after the dissolution of the rock salt.  In order to test these hypotheses, we intend to carry out analogue experiments in which we try to model a squeezed diapir. In a parameter study, the thickness and the material of the covering layer simulating the caprock will be varied to assess possible differences in the deformation patterns.</p>

New Structural Evolution Model for the North Kuwait Carbonate Fields and its Implication for Fracture Characterisation and Modelling

2014 ◽  
Author(s):  
Pascal Richard ◽  
Loic Bazalgette ◽  
Vijaya Kumar Kidambi ◽  
Kamran Laiq ◽  
Allan Odreman ◽  
...  
Keyword(s):  
Structural Evolution ◽  
Evolution Model ◽  
The North

Geographical restriction as a guide to the causes of extinction: the case of the cold northern oceans during the Neogene

Paleobiology ◽  
1989 ◽  
Vol 15 (4) ◽  
pp. 335-356 ◽  
Author(s):  
Geerat J. Vermeij
Keyword(s):  
Primary Productivity ◽  
North Pacific ◽  
Early Pleistocene ◽  
Northwestern Pacific ◽  
Supporting Evidence ◽  
Geographical Patterns ◽  
The North ◽  
The Pacific ◽  
Late Neogene ◽  
The North Pacific

Geographical restriction to refuges implies the regional extinction of taxa in areas of the previous range falling outside the refuge. A comparison of the circumstances in the refuge with those in areas from which the taxa were eliminated is potentially informative for pinpointing the causes of extinction. A synthesis of data on the geographical and stratigraphical distributions of cool-water molluscs of the North Pacific and North Atlantic Oceans during the late Neogene reveals four patterns of geographical restriction, at least two of which imply that climatic cooling was not the only cause of extinction during the last several million years. These four patterns are (1) the northwestern Pacific restriction, involving 15 taxa whose amphi-Pacific distributions during the late Neogene became subsequently restricted to the Asian side of the Pacific; (2) the northwestern Atlantic restriction, involving six taxa whose early Pleistocene distribution is inferred to have been amphi-Atlantic, but whose present-day and late Pleistocene ranges are confined to the northwestern Atlantic; (3) a vicariant Pacific pattern, in which many ancestral amphi-Pacific taxa gave rise to separate eastern and western descendants; and (4) the circumboreal restriction, involving six taxa whose early Pleistocene distribution, encompassing both the Atlantic and Pacific Oceans, became subsequently limited to the North Pacific. Like the Pliocene extinctions in the Atlantic, previously studied by Stanley and others, the vicariant Pacific pattern is most reasonably interpreted as having resulted from regional extinction of northern populations in response to cooling. The northwestern Pacific and Atlantic restrictions, however, cannot be accounted for in this way. In contrast to the northeastern margins of the Pacific and Atlantic, the northwestern margins are today characterized by wide temperature fluctuations and by extensive development of shore ice in winter. Northeastern, rather than northwestern, restriction would be expected if cooling were the overriding cause of regional extinction. Among the other possible causes of extinction, only a decrease in primary productivity can account for the observed northwestern and circumboreal patterns of restriction. Geographical patterns of body size and the distribution of siliceous deposits provide supporting evidence that primary productivity declined after the Miocene in the northeastern Pacific, but remained high in the northwestern Pacific, and that productivity in the Pacific is generally higher than it is in the Atlantic. The patterns of geographical restriction in the northern oceans thus provide additional support to previous inferences that reductions in primary productivity have played a significant role in marine extinctions.

scholarly journals Structural analysis of the Rio Preto fold belt (northwestern Bahia / southern Piauí), a doubly-vergent asymmetric fan developed during the Brasiliano Orogeny

2014 ◽  
Vol 86 (3) ◽  
pp. 1101-1113 ◽  
Author(s):  
FABRÍCIO A. CAXITO ◽  
ALEXANDRE UHLEIN ◽  
LUIZ F.G. MORALES ◽  
MARCOS EGYDIO-SILVA ◽  
JULIO C.D. SANGLARD ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Structural Evolution ◽  
Shear Zones ◽  
Central Compartment ◽  
Strike Slip ◽  
Fold Belt ◽  
Main Structure ◽  
The North ◽  
Brasiliano Orogeny ◽  
Analog Models

The Rio Preto fold belt borders the northwestern São Francisco craton and shows an exquisite kilometric doubly-vergent asymmetric fan structure, of polyphasic structural evolution attributed exclusively to the Brasiliano Orogeny (∼600-540 Ma). The fold belt can be subdivided into three structural compartments: The Northern and Southern compartments showing a general NE-SW trend, separated by the Central Compartment which shows a roughly E-W trend. The change of dip of S2, a tight crenulation foliation which is the main structure of the fold belt, between the three compartments, characterizes the fan structure. The Central Compartment is characterized by sub-vertical mylonitic quartzites, which materialize a system of low-T strike slip shear zones (Malhadinha – Rio Preto Shear Zone) crosscutting the central portion of the fold belt. In comparison to published analog models, we consider that the unique structure of the Rio Preto fold belt was generated by the oblique, dextral-sense interaction between the Cristalândia do Piauí block to the north and the São Francisco craton to the south.

scholarly journals EVOLUTION OF KARAKORAM SEQUENCE, HUNZA VALLEY NE PAKISTAN: EVIDENCES FROM FIELD MAPPING AND MICRO-ANALYTICAL WORK

2020 ◽  
Vol 5 ◽  
pp. 19
Author(s):  
S. S. Baig ◽  
C. Xue ◽  
Masroor Alam ◽  
Naeem Ullah ◽  
M. Alam ◽  
...  
Keyword(s):  
Geological Mapping ◽  
Central Portion ◽  
High Grade ◽  
Metamorphic Complex ◽  
Field Mapping ◽  
The North ◽  
Analytical Work ◽  
History Of ◽  
Micro Analysis ◽  
East West

The Karakoram metamorphic Complex (KMC) in the southern Karakoram block is one of the best examples of Barrovian type metamorphism that comprises numerous exhumed metapelite units where a series of low to high grade (green schist to sillimanite facie) rocks are exposed. This sequence shows a complex polyphase history of metamorphism and deformation which offer deeper understanding of collision orogeny. Karakoram metamorphic Complex contains metapelites, meta-carbonates, meta-igneous and amphibolite layers, cross-cut by granite sheets in the northern part. This complex is bounded to the north by the Hunza plutonic unit which is the central portion of the massive east-west trending Karakoram axial batholith and to the southwest by the Main Karakoram thrust (MKT). In this contribution, we provide detail geological mapping, petrography, geochemistry and micro-analytical work using Electron Prob-micro analysis in the central Hunza Valley.

scholarly journals Deep structure of the Anapa flexural-rupture zone, Western Caucasus

2019 ◽  
pp. 3-11
Author(s):  
E. A. Rogozhin ◽  
A. V. Gorbatikov ◽  
Yu. V. Kharazova ◽  
M. Yu. Stepanova ◽  
J. Chen ◽  
...  
Keyword(s):  
Deep Structure ◽  
Sedimentary Cover ◽  
Western Caucasus ◽  
Tectonic Structures ◽  
Deep Roots ◽  
Near Surface ◽  
North West ◽  
The North ◽  
Deep Faults ◽  
Tectonic Zones

In the period from 2007 to 2017 complex geological and geophysical studies were carried out in the three largest flexural-rupture fault zones in the North-West Caucasus (Anapa, Akhtyrka and Moldavan). The micro-seismic sounding (MSM) was used as the main geophysical method. Studies with the help of MSM allowed us to identify the features of the deep structure of the earth’s crust in the study area and to associate them with specific tectonic structures on the surface.The binding was carried out by harmonizing the results of the MSM and the parameters of the section of the sedimentary cover and crustal boundaries according to the drilling data and the work previously performed by the reflected wave method (MOVZ). It was found that the Anapa flexure and longitudinal tectonic zones have clear deep roots, and also separate the pericline of the North-Western Caucasus from the Taman Peninsula and from the lowered blocks of the Northern slope of the folded system.Faults in the study area are divided into: (1) deep faults of the Caucasian stretch, penetrating into the lower crust and even to the upper mantle, and (2) near-surface faults, do not extend to the depths beyond the thickness of the sedimentary cover. The seismogenic role of these tectonic disturbances in the studied seismically active region has been determined.

scholarly journals Identifikasi Keterdapatan Mineral Radioaktif pada Urat-Urat Magnetit di Daerah Ella Ilir, Melawi, Kalimantan Barat

EKSPLORIUM ◽  
2019 ◽  
Vol 40 (1) ◽  
pp. 33
Author(s):  
Ngadenin Ngadenin ◽  
Frederikus Dian Indrastomo ◽  
Widodo Widodo ◽  
Kurnia Setiawan Widana
Keyword(s):  
Iron Ore ◽  
Biotite Granite ◽  
Ore Deposits ◽  
Geological Mapping ◽  
Granitic Rocks ◽  
Metamorphic Rocks ◽  
West Kalimantan ◽  
The North ◽  
Iron Ore Deposits ◽  
Radioactive Minerals

ABSTRAKElla Ilir secara administratif terletak di Kabupaten Melawi, Kalimantan Barat. Geologi regional daerah Ella Ilir tersusun atas batuan malihan berumur Trias–Karbon yang diterobos oleh batuan granitik berumur Yura dan Kapur. Keterdapatan mineral radioaktif di daerah tersebut terindikasi dari radioaktivitas urat-urat magnetit pada batuan malihan berumur Trias–Karbon dengan kisaran nilai 1.000 c/s hingga 15.000 c/s. Tujuan dari penelitian ini adalah menentukan jenis cebakan mineral bijih dan mengidentifikasi keterdapatan mineral radioaktif pada urat-urat bijih magnetit di daerah Ella Ilir. Metode yang digunakan adalah pemetaan geologi, pengukuran radioaktivitas, analisis kadar uranium, dan analisis mineragrafi beberapa sampel urat bijih magnetit. Litologi daerah penelitian tersusun oleh kuarsit biotit, metatuf, metabatulanau, metapelit, granit biotit, dan riolit. Sesar sinistral barat-timur dan sesar dekstral utara-selatan merupakan struktur sesar yang berkembang di daerah ini. Komposisi mineral urat-urat magnetit terdiri dari mineral-mineral bijih besi, sulfida, dan radioaktif. Mineral bijih besi terdiri dari magnetit, hematit, dan gutit. Mineral sulfida terdiri dari pirit, pirhotit, dan molibdenit sedangkan mineral radioaktif terdiri dari uraninit dan gumit. Keterdapatan urat-urat bijih magnetit dikontrol oleh litologi dan struktur geologi. Urat-urat magnetit pada metabatulanau berukuran tebal (1,5–5 m), mengisi rekahan-rekahan yang terdapat di sekitar zona sesar. Sementara itu, urat-urat magnetit pada metapelit berukuran tipis (milimetrik–sentimetrik), mengisi rekahan-rekahan yang sejajar dengan bidang sekistositas. Cebakan mineral bijih di daerah penelitian adalah cebakan bijih besi atau cebakan bijih magnetit berbentuk urat karena proses hidrotermal magmatik.ABSTRACTElla Ilir administratively located in Melawi Regency, West Kalimantan. Regional geology of Ella Ilir area is composed of metamorphic rocks in Triassic–Carboniferous age which are intruded by Jurassic and Cretaceous granitic rocks. Radioactive minerals occurences in the area are indicated by magnetite veins radioactivities on Triassic to Carboniferous metamorphic rocks whose values range from 1,000 c/s to 15,000 c/s. Goal of the study is to determine the type of ore mineral deposits and to identify the presence of radioactive mineral in magnetite veins in Ella Ilir area. The methods used are geological mapping, radioactivity measurements, analysis on uranium grades, and mineragraphy analysis of severe magnetite veins samples. Lithologies of the study area are composed by biotite quartzite, metatuff, metasilt, metapellite, biotite granite, and ryolite. The east-west sinistral fault and the north-south dextral fault are the developed fault structures in this area. Mineral composition of magnetite veins are consists of iron ore, sulfide, and radioactive minerals. Iron ore mineral consists of magnetite, hematit, and goetite. Sulfide minerals consist of pyrite, pirhotite, and molybdenite, while radioactive minerals consist of uraninite and gummite. The occurences of magnetite veins are controlled by lithology and geological structures. The magnetite veins in metasilt are thick (1.5–5 m), filled the fractures in the fault zone. Meanwhile, the magnetite veins in metapellite are thinner (milimetric–centimetric), filled the fractures that are parallel to the schistocity. The ore deposits in the study area are iron ore deposits or magnetite ore deposits formed by magmatic hydrothermal processes. 

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