The geology of Myanmar is shaped by dramatic, ongoing tectonic processes controlled by shifting tectonic components as the Indian Plate slides northwards and towards Southeast Asia. [1] Myanmar spans across parts of three tectonic plates (the Indian Plate, Burma microplate and Shan Thai Block) separated by north-trending faults. To the west, a highly oblique subduction zone separates the offshore Indian Plate from the Burma microplate, which underlies most of the country. In the center-east of Myanmar, a right lateral strike slip fault extends from south to north across more than 1,000 km (620 mi). [2] These tectonic zones are responsible for large earthquakes in the region. [1] The India-Eurasia plate collision which initiated in the Eocene provides the last geological pieces of Myanmar, [3] and thus Myanmar preserves a more extensive Cenozoic geological record as compared to records of the Mesozoic and Paleozoic eras. Myanmar is physiographically divided into three regions: the Indo-Burman Range, Myanmar Central Belt and the Shan Plateau; [4] these all display an arcuate shape bulging westwards. The varying regional tectonic settings of Myanmar not only give rise to disparate regional features, but also foster the formation of petroleum basins and a diverse mix of mineral resources. [5]
Myanmar is classified into three physiographical regions, each region spans over Myanmar in near NS direction, from west to east is: the Indo-Burman folded mountain ranges, the Myanmar Central Belt (MCB) and the Shan Plateau. [4] To the north of Myanmar, the eastern Himalaya syntaxis bounds the three physiographical region. [6]
Myanmar has a complex arc-shaped deformation structure, which is probably due to the a combination of various forces. [7] Aside from the subduction system on the west and the strike-slip fault system in the central Myanmar, another major contribution may be the crustal flow from the Tibet Plateau. [7] The Tibet Plateau is located at the north of Myanmar and has been considerably thickened since the Eocene. [7] A large amount of potential energy stored within the thickened Tibetan crust was released, and resulted in a crustal flow around the eastern Himalaya Syntaxis. [8] The crustal flow runs towards west and into the central region of Myanmar. This crustal flow, along with the accretionary wedge in the subduction system, may have participated in the late Neogene uplift of Indo-Burman Range. [7]
The Indo-Burman Range sits at the convergent boundary of the Indian and Burma-micro Plates in Myanmar. The subduction between the two plates resulted in the development of accretionary wedges, in order to accommodate the EW shortening along the convergent boundary. Later, thrusting, folding and uplifting formed the Indo-Burman Ranges. [9] The mountain belt comprises various mountains: the Arakan-Yoma mountains and the Chin, Naga, Maniour, Lushai and Patkai hills. [10] The Indo-Burman Range merged with Eastern Himalayan Syntaxis further north, submerged into the Andaman Sea, and resurfaced as Andaman Islands further south. [4]
The Indo-Burman Range bulges towards the west at the center (about 22°N), forming an arc-shaped structure. [7] This arc-shaped structure implies restriction on the convergent motion along the Indian-Burma boundary, therefore the collision intensity varies along the range. [10]
The collision is at a maximum at the center of the Indo-Burman Range around 24°N, which is presented with a broad, high range (up to 20 km wide) and evolves to narrow, low hills in the south (16°N). [10] The collision strikes in NW-SE at the northern part of the Indo-Burman Range (Naga Domain). [11]
The 1000 km Myanmar Central Belt consists of a series of Cenozoic sub-basins between the Indo-Burman Range (west) and Sagaing Fault (east). [12] These basins are generally considered as forearc/back arc basin couplet of the Indo-Burma subduction system. [7] The eight major tertiary sub-basins within the Myanmar Central Belt are Hukwang, Chindwin, Shwebo, Salin, Pyay Embayment, Irrawaddy Delta, Bago-Yoma, and Sittaung Basin. [13]
A variety of structural features—such as oblique-reverse faults, strike slip faults and normal faults—can be found within the central belt. [12] The abundant evidence of shear zones suggests the Myanmar Central Belt has undergone severe internal deformation. The exposed metamorphic lineation along the belt [14] indicates different motions within the central belt: (1) dextral pull apart geometry trending in a north-northwest direction during Oligocene to early Miocene forming an "en-echelon" pull-apart basin: [12] (2) fault-propagated folds cored in a west-dipping thrust fault in the basin center implies an east-west trending transpressional deformation from Pliocene-Pleistocene onwards. [12]
The Shan Plateau, with an average elevation of 1 kilometre (0.62 mi), forms the eastern highlands of Myanmar. [15] It provides the major topographic relief in Myanmar and it extends towards the southeast to Thailand. [16] The plateau, unlike other regions Myanmar, comprises thick successions of Paleozoic, Mesozoic and even Precambrian sedimentary rocks. [15] The folding, thrusting and uplifting of the Shan Plateau is probably coeval with the transpressional deformation along the Myanmar Central Belt during the commencement of the India-Eurasia collision. [16]
Situated on the east of the Sagaing fault and the west of Shan plateau, the Mogok Metamorphic Belt (MMB) lies at the foothill of Shan Scarp. It runs in a near north-south direction and extends over 1500 km with an average width of 24–40 km. [4] The meta-sedimentary and meta-intrusive belt is composed of marbles, schists, gneisses of upper amphibolite, with locally granulite facies intruded by a deformed granodiorite pluton and pegmatites. [2] The belt also shows evidence for ductile stretching along the north-northwest-south-southeast direction, e.g. lineation, sheath folds and "pencil-like" mullions. [2] Various radiometric dating confirms the age of Mogok Metamorphic Belt predates the Sagaing Fault, and the shear heating of Sagaing Fault has no contribution to the formation of Mogok Metamorphic Belt. [2]
Searle (2007) suggested a five-phased metamorphism and magmatism along the Mogok Metamorphic Belt. [2]
Note: Ma (mega-annum) is a million years
The Indo-Burman Range is a sedimentary belt mainly consisted of Cenozoic flysch sediments [17] and a core of Mesozoic ophiolites dated back to late Jurassic overlain on a thick Mesozoic sequence. All the above unconformity lies on a metamorphic basement dated back to pre-Triassic. [6]
The core Mesozoic ophiolites consists of serpentinite peridotites, pillow basalts and red cherts etc. [6] The obduction of ophiolites is interpreted as the closure of several Neo-Tethys between the Shan-Thai block, Burma microplate and Indian Plate. [7]
The sedimentary sequence overlain by the ophiolites ranges from Late Triassic to Orbitoides-bearing Late Cretaceous carbonates and shales, [7] where part of the sedimentary sequence has undergone high pressure/low temperature blue-schist metamorphism. [17]
The pre-Triassic metamorphic basement composed of Kampetlet schist and gneisses were exposed in the Mount Victoria area in Myanmar. [6] The flysch type sediments in the western flank of the Indo-Burman Range are relatively younger than the folded and thrusted eastern flank. [18]
The Cenozoic pull-apart basins along the Myanmar Central Belt (MCB) are filled-up with 15 km thick Late Cretaceous and Eocene to Late Miocene sediments. [6]
Belonging to the rigid Shan-Thai block, the Shan Plateau is composed of consolidated partially low-grade metamorphic and Precambrian crystalline rocks [6] overlain with a thick succession of Palaeozoic and Mesozoic sedimentary rocks. [15]
The tectonic setting of Myanmar consists of a highly oblique convergence on the western boundary, a dextral (right lateral) strike-slip fault in the centre of Myanmar defining the Burma-Sunda boundary and the spreading of Andaman Sea Ridge in the south. [3]
From the Eocene epoch onward, the northward movement of Indian Plate collided with the Eurasian Plate and generated the Himalaya Orogenic belt. [19] The relative motion of the Indian plate against the Eurasian plate (Sunda) has two components (1) 36 mm/year right lateral strike-slip, trending in N10°E direction; (2) 7–9 mm/year east-west convergence. [20] The convergent motion is absorbed by a highly oblique subduction zone between the Indian plate and Burma-micro plate and internal deformation in the centre of Myanmar on the Sagaing Fault. [7]
The obliquity of the Indo-Burma convergent plate boundary (Arakan Trench and Andaman Trench) increases further northwards, with a minimum angle of 58° at 20°N latitude to 70° near 22°N latitude, and rapidly increases to 90° near 24°N latitude and over 90° to further North. [3] The boundary between Indo-Burma region runs further southward into the Bay of Bengal and joins the Sumatra Trench. [3]
In order to accommodate the India-Eurasia collision, extensive fault systems can be found in Myanmar. The following introduces two of the major fault systems.
The 20mm/yr dextral (right lateral) strike slip Sagaing Fault detaches the Burma microplate from the Sunda plate. [21] The arc-parallel fault spans over 1400 km in a north-south direction, remarkably linear for the central 700 km (at 17°N to 23°N latitude) and forms a slight arc shape swinging N10°E and N170°E direction at the north and south ends of the fault respectively. [21] Northward, the Sagaing fault terminates at the Jade Mine belt (~ 24.5°N) and splays into a 200 km width compressive horsetail structure. [21] Southward, it is connected to the active Andaman spreading rift. [21] The onset of seafloor spreading on the Andaman rift puts a minimum 4.5 Ma age constraint on the Sagaing Fault. [22]
The total displacement of the right lateral strike slip fault remains controversial. Curray et al. (1979) suggested a total 460 km of displacement since Miocene; [23] whereas Khin Zaw (1990) proposed 250 km since post Lower Miocene. [24] Guillaume & Rangin (2003) deduced approximately 100 km by constraining a continuous 20mm/yr right lateral strike slip since 4-5Ma. [16]
The topographic boundary separating the Myanmar Central Basin (MCB) and the Shan Plateau (or Eastern Highland) [16] is referred as the Shan Scarp. The abrupt elevation over a short distance (up to 1.8 km over few km) harbors the trace of reverse faults and largely overturned folds. [16] The Shan Scarp aligns parallel to the Sagaing fault on the east. [16] The general trend of reverse fault strikes is N20°W and dips in the east-northeast direction; where some N20°E striking normal faults were identified along the fault scarp (at 21°N to 22°N latitude), north of Mandalay. [16] Dextral (right lateral) strike slip motion is also observed along the fault scarp, this motion is reasonably expected due to the nearby right lateral Sagaing fault. Southward, the Shan Scarp ends at the junction with the Three Pagodas fault. [21]
Along the foothills of the Shan Scarp, steady-state stretching ductile deformation trending in NNW-SSE direction was identified and is compatible with the extensive force that generates the en-echelon pull apart basin in Myanmar Central Belt (MCB). [16]
The above evidence suggests ductile deformation along Myanmar Central Belt (MCB) should occur prior to the brittle deformation along Sagaing fault and the Shan Scarp fault.
Myanmar lies on the boundary of three tectonic plates (India, Burma-micro and Sunda Plate), thus its geological evolution is highly dependent on the plate tectonic events in this region. In the following, the geological evolution of Myanmar will be explained in the order of geological timescale. Only major tectonic events are recorded with some missing timescale where no major events occurred.
In the early Permian, a continental block rifted from Gondwanaland. [26] The continental plate has been variously termed: Shan-Thai, [26] Sibumasu, [27] or Sinoburmalaya. This continental block harbors features of glaciogenic marine diamictite unit, indicating its origin from Gondwanaland. [25] The Shan-Thai block was probably located northwest of Australia plate during the Gondwanaland period. [25]
In the mid-late Triassic, the Shan-Thai block collided with the Indo-China block, and under-thrusted an ophiolite and associated arc system in the northeast. [15] A foreland thrust belt developed along the collision of the two blocks and laid the foundation of the Shan Plateau. [15]
A thick flysch unit with fossils and deltaic sediments were deposited along the northeastern Shan-Thai block (now Shan Plateau) with the closing of a shallow sea region between the two blocks prior to collision. [6] Large-scale intrusion of granitoid plutons and batholiths were induced by oceanic subduction; [6] and partial melting of metasedimentary rocks within the foreland thrust belt led to tin-tungsten mineralization (the Central Tin Belt). [15]
The India Plate departed from the Gondwanaland and headed northwards at a rate of 10 cm/yr during the Cretaceous Period. [7]
The rifted Burma-microplate from Gondwanaland also docked against Shan-Thai block and together formed part of the Sunda plate approximately in the period. [15] There is a discrepancy for the time of the Burma-Shan-Thai collision: Mitchell (1989) says Early Cretaceous yet changes to Mid-Eocene in 1993; [18] Hutchison (1989) says Late Cretaceous; [28] and Acharyya (1998) says late Oligocene. [29]
In early Eocene, the start of a hard continent-to-continent collision between India and the Eurasia Plate led to the formation of the Himalayan Orogeny. [30] On the eastern margin of the India plate, high oblique subduction occurs between the boundary of India and the Burma-micro plate. [31]
Between late Eocene to Miocene, the Burma and Shan-Thai block rotated 30° to 40° clockwise, to accommodate the major collision along the plate boundary. [30] This resulted in the trend of arc shifting from east-west to the north-south direction.
The subduction boundary forms an accretionary prism [30] and eventually with thrusting and folding forms the Indo-Burma Range. [18]
In late Miocene to Pliocene, the slab detachment of Burma-microplate beneath the Shan-Thai block induced in a mantle window into the slab and resulted in alkaline and calk-alkaline volcanism along the Myanmar Central Belt. [32]
In the late Miocene (10 million years ago), the Myanmar Central Belt underwent a major regional plate kinematic reorganization transition. [16] The tectonic regimes transform from northwest-southeast extensional force to basin inversion and was followed by a major uplift event caused by east-west compression during Plio-Pleistocene period. [33]
Myanmar hosts a variety of ore-deposits with economic significance and global recognition. It is a global source of true jade and produces some of the world's finest rubies, [5] with mines in the Mogok Valley providing the bulk of the world's supply for centuries. [34]
Myanmar's mineral deposits into different distinct metallogenic provinces by various workers. [5] The following outlines the nine major ones:
The hydrocarbon basins in Myanmar are mostly situated in the Central Myanmar Belt, e.g. Salin Basin, Chindwin Basin and Hukawng Basin over 1000 km. [43] The formations that compose the hydrocarbon basins are sedimentary rocks of Eocene through mid-Mioceneand sealed with interbedded Oligocene and Miocene shales and clays. [43]
The Basin and Range Province is a vast physiographic region covering much of the inland Western United States and northwestern Mexico. It is defined by unique basin and range topography, characterized by abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins. The physiography of the province is the result of tectonic extension that began around 17 million years ago in the early Miocene epoch.
The Laramide orogeny was a time period of mountain building in western North America, which started in the Late Cretaceous, 80 to 70 million years ago, and ended 55 to 35 million years ago. The exact duration and ages of beginning and end of the orogeny are in dispute. The Laramide orogeny occurred in a series of pulses, with quiescent phases intervening. The major feature that was created by this orogeny was deep-seated, thick-skinned deformation, with evidence of this orogeny found from Canada to northern Mexico, with the easternmost extent of the mountain-building represented by the Black Hills of South Dakota. The phenomenon is named for the Laramie Mountains of eastern Wyoming. The Laramide orogeny is sometimes confused with the Sevier orogeny, which partially overlapped in time and space.
The geology of the Himalayas is a record of the most dramatic and visible creations of the immense mountain range formed by plate tectonic forces and sculpted by weathering and erosion. The Himalayas, which stretch over 2400 km between the Namcha Barwa syntaxis at the eastern end of the mountain range and the Nanga Parbat syntaxis at the western end, are the result of an ongoing orogeny — the collision of the continental crust of two tectonic plates, namely, the Indian Plate thrusting into the Eurasian Plate. The Himalaya-Tibet region supplies fresh water for more than one-fifth of the world population, and accounts for a quarter of the global sedimentary budget. Topographically, the belt has many superlatives: the highest rate of uplift, the highest relief, among the highest erosion rates at 2–12 mm/yr, the source of some of the greatest rivers and the highest concentration of glaciers outside of the polar regions. This last feature earned the Himalaya its name, originating from the Sanskrit for "the abode of the snow".
The Sevier orogeny was a mountain-building event that affected western North America from northern Canada to the north to Mexico to the south.
The Lewis Overthrust is a geologic thrust fault structure of the Rocky Mountains found within the bordering national parks of Glacier in Montana, United States and Waterton Lakes in Alberta, Canada. The structure was created due to the collision of tectonic plates about 59-75 million years ago that drove a several mile thick wedge of Precambrian rock 50 mi (80 km) eastwards, causing it to overlie softer Cretaceous age rock that is 1300 to 1400 million years younger.
The North China Craton is a continental crustal block with one of Earth's most complete and complex records of igneous, sedimentary and metamorphic processes. It is located in northeast China, Inner Mongolia, the Yellow Sea, and North Korea. The term craton designates this as a piece of continent that is stable, buoyant and rigid. Basic properties of the cratonic crust include being thick, relatively cold when compared to other regions, and low density. The North China Craton is an ancient craton, which experienced a long period of stability and fitted the definition of a craton well. However, the North China Craton later experienced destruction of some of its deeper parts (decratonization), which means that this piece of continent is no longer as stable.
In the geology of the Philippines, the Philippine Mobile Belt is a complex portion of the tectonic boundary between the Eurasian Plate and the Philippine Sea Plate, comprising most of the country of the Philippines. It includes two subduction zones, the Manila Trench to the west and the Philippine Trench to the east, as well as the Philippine Fault System. Within the Belt, a number of crustal blocks or microplates which have been shorn off the adjoining major plates are undergoing massive deformation.
The Andean orogeny is an ongoing process of orogeny that began in the Early Jurassic and is responsible for the rise of the Andes mountains. The orogeny is driven by a reactivation of a long-lived subduction system along the western margin of South America. On a continental scale the Cretaceous and Oligocene were periods of re-arrangements in the orogeny. The details of the orogeny vary depending on the segment and the geological period considered.
The geology of Russia, the world's largest country, which extends over much of northern Eurasia, consists of several stable cratons and sedimentary platforms bounded by orogenic (mountain) belts.
The 1762 Arakan earthquake occurred at about 17:00 local time on 2 April, with an epicentre somewhere along the coast from Chittagong to Arakan in modern Myanmar. It had an estimated moment magnitude between 8.5 and 8.8 and a maximum estimated intensity of XI (Extreme). It triggered a local tsunami in the Bay of Bengal and caused at least 200 deaths. The earthquake was associated with major areas of both uplift and subsidence. It is also associated with a change in course of the Brahmaputra River to from east of Dhaka to 150 kilometres (93 mi) to the west via the Jamuna River.
High pressure terranes along the ~1200 km long east-west trending Bangong-Nujiang suture zone (BNS) on the Tibetan Plateau have been extensively mapped and studied. Understanding the geodynamic processes in which these terranes are created is key to understanding the development and subsequent deformation of the BNS and Eurasian deformation as a whole.
The Kutai sedimentary basin extends from the central highlands of Borneo, across the eastern coast of the island and into the Makassar Strait. With an area of 60,000 km2, and depths up to 15 km, the Kutai is the largest and deepest Tertiary age basin in Indonesia. Plate tectonic evolution in the Indonesian region of SE Asia has produced a diverse array of basins in the Cenozoic. The Kutai is an extensional basin in a general foreland setting. Its geologic evolution begins in the mid Eocene and involves phases of extension and rifting, thermal sag, and isostatic subsidence. Rapid, high volume, sedimentation related to uplift and inversion began in the Early Miocene. The different stages of Kutai basin evolution can be roughly correlated to regional and local tectonic events. It is also likely that regional climate, namely the onset of the equatorial ever wet monsoon in early Miocene, has affected the geologic evolution of Borneo and the Kutai basin through the present day. Basin fill is ongoing in the lower Kutai basin, as the modern Mahakam River delta progrades east across the continental shelf of Borneo.
The geology of the Dominican Republic is part of the broader geology of Hispaniola with rocks formed from multiple island arcs, colliding with North America.
The subduction tectonics of the Philippines is the control of geology over the Philippine archipelago. The Philippine region is seismically active and has been progressively constructed by plates converging towards each other in multiple directions. The region is also known as the Philippine Mobile Belt due to its complex tectonic setting.
The geology of New Caledonia includes all major rock types, which here range in age from ~290 million years old (Ma) to recent. Their formation is driven by alternate plate collisions and rifting. The mantle-derived Eocene Peridotite Nappe is the most significant and widespread unit. The igneous unit consists of ore-rich ultramafic rocks thrust onto the main island. Mining of valuable metals from this unit has been an economical pillar of New Caledonia for more than a century.
Oblique subduction is a form of subduction for which the convergence direction differs from 90° to the plate boundary. Most convergent boundaries involve oblique subduction, particularly in the Ring of Fire including the Ryukyu, Aleutian, Central America and Chile subduction zones. In general, the obliquity angle is between 15° and 30°. Subduction zones with high obliquity angles include Sunda trench and Ryukyu arc.
The 1858 Prome earthquake occurred on August 24 at 15:38 local time in British Burma. The earthquake occurred with a magnitude of 7.6–8.3 on the moment magnitude scale. It had an epicenter in near the city of Pyay (Prome), Bago. The shock was felt with a maximum Modified Mercalli intensity of XI (Extreme) for about one minute. Severe damage was reported in Bago, and off the coast of Rakhine, an island sunk.
The Ryukyu Arc is an island arc which extends from the south of Kyushu along the Ryukyu Islands to the northeast of Taiwan, spanning about 1,200 kilometres (750 mi). It is located along a section of the convergent plate boundary where the Philippine Sea Plate is subducting northwestward beneath the Eurasian Plate along the Ryukyu Trench. The arc has an overall northeast to southwest trend and is located northwest of the Pacific Ocean and southeast of the East China Sea. It runs parallel to the Okinawa Trough, an active volcanic arc, and the Ryukyu Trench. The Ryukyu Arc, based on its geomorphology, can be segmented from north to south into Northern Ryukyu, Central Ryukyu, and Southern Ryukyu; the Tokara Strait separates Northern Ryukyu and Central Ryukyu at about 130˚E while the Kerama Gap separates Central Ryukyu and Southern Ryukyu at about 127 ˚E. The geological units of the arc include igneous, sedimentary, and metamorphic rocks, ranging from the Paleozoic to Cenozoic in age.
Jacques Malavieille is a French geologist. He is known for research combining geological fieldwork with analog modeling, and with some computer modeling, for scientific understanding of lithospheric deformation.
The Indo-Burman Ranges (IBR), also known as the Indo-Myanmar Ranges, a mountain chain that form the boundary between the Indian subcontinent and mainland southeast Asia. This geological feature sits at the convergent boundary of the Indian Plate and the Burma Plate. The Indo-Burman Range merged with Eastern Himalayan Syntaxis further north, submerged into the Andaman Sea, and resurfaced as Andaman Islands further south.
{{cite journal}}
: CS1 maint: multiple names: authors list (link){{cite journal}}
: Cite journal requires |journal=
(help)CS1 maint: multiple names: authors list (link){{cite journal}}
: Cite journal requires |journal=
(help){{cite web}}
: CS1 maint: multiple names: authors list (link)