The Karakoram fault is an oblique-slip fault system in the

Himalaya The Himalayas, or Himalaya ( ), is a mountain range in Asia, separating the plains of the Indian subcontinent from the Tibetan Plateau. The range has some of the Earth's highest peaks, including the highest, Mount Everest. More than 100 pea ...

n region across

India India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...

and Asia. The slip along the fault accommodates radial expansion of the Himalayan arc, northward indentation of the

Pamir Mountains The Pamir Mountains are a Mountain range, range of mountains between Central Asia and South Asia. They are located at a junction with other notable mountains, namely the Tian Shan, Karakoram, Kunlun Mountains, Kunlun, Hindu Kush and the Himalaya ...

, and eastward lateral extrusion of the

Tibetan plateau The Tibetan Plateau, also known as the Qinghai–Tibet Plateau or Qingzang Plateau, is a vast elevated plateau located at the intersection of Central Asia, Central, South Asia, South, and East Asia. Geographically, it is located to the north of H ...

. Current plate motions suggest that the convergence between the

Indian plate The Indian plate (or India plate) is or was a minor tectonic plate straddling the equator in the Eastern Hemisphere. Originally a part of the ancient continent of Gondwana, the Indian plate broke away from the other fragments of Gondwana an ...

and the Eurasian plate is around 44±5 mm per year in the western Himalaya-Pamir region and approximately 50±2 mm per year in the eastern Himalayan region.

Origin

The creation of the Karakoram fault started with the closing of the ancient

Tethys Ocean The Tethys Ocean ( ; ), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean during much of the Mesozoic Era and early-mid Cenozoic Era. It was the predecessor to the modern Indian Ocean, the Mediterranean Sea, and the Eurasia ...

seaway which once separated the two modern continents of Asia and India. The Karakoram fault itself does not trace a plate boundary, except for where it possibly ends in the

Indus-Yarlung Suture Zone The Indus-Yarlung suture zone or the Indus-Yarlung Tsangpo suture is a tectonic suture in southern Tibet and across the north margin of the Himalayas which resulted from the collision between the Indian Plate and the Eurasian Plate starting ab ...

. The original thrusting occurred by linking existing

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. I ...

s in what is now the

starting between 17 and 20 million years ago.

Evolution

The Karakoram fault was a right lateral slip fault starting approximately 20 million years ago. Approximately 14 million years ago the fault changed to a predominately normal fault. This conclusion is based on argon dating. Around 10-11 million years ago the Karakoram fault had become trans-tensional and extended southwest into Tibet. The southwest extension is marked by the Karakoram fault crossing the active South Kailas Thrust in the vicinity of present-day Mount Kailas.

Length

It is suggested that a late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

granite Granite ( ) is a coarse-grained (phanerite, phaneritic) intrusive rock, intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly coo ...

batholith A batholith () is a large mass of intrusive rock, intrusive igneous rock (also called plutonic rock), larger than in area, that forms from cooled magma deep in the Earth's crust. Batholiths are almost always made mostly of felsic or intermediate ...

had been offset 1000 km dextrally along the Karakoram Fault based on mapping in the central Karakoram, in nearby Ladakh-Zanskar, and in south Tibet. Some researchers suggest that this might be incorrect due to associating granite that was never part of the same batholith. Others researchers work have shown 600 km of right lateral slip since 23 million years ago, and possibly starting 34 million years ago, based on U-Pb dating. Slip in this model has been transferred into the Indus-Yalu suture zone, as well as large scale

boudinage upBoudinaged quartz vein in shear foliation, Starlight Pit, Fortnum Gold Mine, Western Australia. Boudinage is a geological term for structures formed by extension, where a rigid tabular body such as hornfels, is stretched and deformed ami ...

. Research in the early 1990s suggested that this slip was transferred into the

South Tibetan Detachment The South Tibetan Detachment is one of the major Fault (geology), faults in the Himalaya Mountains. Background Understanding the formation of the Himalayan mountains has been a goal of structural geologists for a long time. Many of the problems an ...

. Another suggestion is that the Karakoram fault is offset at least 500 km as measured by the offset of late Paleozoic granites in the Kunlun batholith. Most researchers tend to agree with the lower slip estimates. A major obstacle in measuring the total offset along the fault is in deciding what is actually a part of the fault and which faults are separate. Currently some researchers believe that the Karakoram fault merges and terminates into the Indus-Yalu suture zone at Mount Kailas. Other researchers also add the Gurla Mandhata detachment, in the South-Eastern segment, to the fault.

North-Western segment

The north-western segment of the Karakoram Fault is far less disputed than other areas. It terminates in the extensions of the Miuji Basin, in the Pamir Mountains, along the border between

Tajikistan Tajikistan, officially the Republic of Tajikistan, is a landlocked country in Central Asia. Dushanbe is the capital city, capital and most populous city. Tajikistan borders Afghanistan to the Afghanistan–Tajikistan border, south, Uzbekistan to ...

and

Xinjiang Xinjiang,; , SASM/GNC romanization, SASM/GNC: Chinese postal romanization, previously romanized as Sinkiang, officially the Xinjiang Uygur Autonomous Region (XUAR), is an Autonomous regions of China, autonomous region of the China, People' ...

provinces. In this north-western segment, the Karakoram Fault currently has predominantly normal fault motion, and right-lateral strike-slip offset. The slip in this section of the Karakoram fault is measured to be approximately 150 km, as measured by the offset of the Aghil formation. The Aghil formation is a fossiliferous carbonate formation. Before entering the Pamir region the Karakoram fault is believed to split into two distinct faults. These faults are the main Karakoram fault itself, and the Achiehkopai fault.

South-Eastern segment

Most people agree that the South-Eastern portion of the fault merges into and parallels the Indus Suture Zone in South West Tibet. The southern segment of the Karakoram Fault shows that only 120 km of dextral motion is evident from offset of geologic features, such as the

Indus River The Indus ( ) is a transboundary river of Asia and a trans-Himalayas, Himalayan river of South Asia, South and Central Asia. The river rises in mountain springs northeast of Mount Kailash in the Western Tibet region of China, flows northw ...

and the South Kailas Thrust, and that the strain in this region is almost entirely accommodated for by a north–south shortening in the Himalaya, just south of the Indus Suture Zone. The Neogene Gar Basin in western Tibet also accommodates slip along the Karakoram fault. The basin lies within the northern approximately 1 km wide area of the fault, and contains listric normal faults. The Gurla Mandhata fault system is thought to be encompassed within the Karakoram fault system at its southern tip, which cause the southern tip of the fault to be approximately 36 km wide. Exhumation along the Gurla Mandhata detachment, which is a low-angle normal-fault system, suggest that the faults have allowed for between 36 and 66 kilometers of slip.

References