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34-643: The source of the river lies in the hills six miles south of the Spīn Ghar range, the source of the Kurram River , to which it runs parallel and finally joins. It borders North Waziristan while the Gomal River borders South Waziristan . The Gambila is an important river for the inhabitants of the Dawar valley, as it serves to irrigate a large area of land that it runs through, particularly that belonging to

68-505: A complete export ban in 1975, which smugglers circumvented. In addition to the actual forestry there is or was a collection economy for pistachio nuts and the edible seeds of Pinus gerardiana . There are a few notable mountain passes in or near the Spīn Ghar mountain range. The famous Khyber Pass crosses a spur of the Spīn Ghar. A second crossing, near Mount Sikaram , is called Peiwar Pass or Gawi Pass and connects Parachinar city on

102-589: A few billion years in age. It is believed that 43% of modern continental crust was formed in the Proterozoic, 39% formed in the Archean, and only 18% in the Phanerozoic . Studies by Condie (2000) and Rino et al. (2004) harvp error: no target: CITEREFRinoKomiyaWindleyet_al2004 ( help ) suggest that crust production happened episodically. By isotopically calculating the ages of Proterozoic granitoids it

136-481: A few plausible models that explain tectonics of the early Earth prior to the formation of Columbia, but the current most plausible hypothesis is that prior to Columbia, there were only a few independent cratons scattered around the Earth (not necessarily a supercontinent, like Rodinia or Columbia). The Proterozoic can be roughly divided into seven biostratigraphic zones which correspond to informal time periods. The first

170-526: A period of increasing crustal recycling, suggesting subduction . Evidence for this increased subduction activity comes from the abundance of old granites originating mostly after 2.6  Ga . The occurrence of eclogite (a type of metamorphic rock created by high pressure, > 1 GPa), is explained using a model that incorporates subduction. The lack of eclogites that date to the Archean Eon suggests that conditions at that time did not favor

204-587: Is Mount Sikaram (Sikaram Sar) , near the Pakistani town of Parachinar in the Kurram Valley . From here it passes to Tari Mangal , Pewar , Alizai , Khewas, Shilawzan, Luqman Khel, Maikay, Chappri Rest House, Zeran, and Upper Khyber Agency . The Spīn Ghar form the watershed between the river systems of the Kabul and Kurram . The closest cities to the Spīn Ghar are Jalalabad to the north; Gardez to

238-542: Is a mountain range to the south of the Hindu Kush . It ranges from eastern Afghanistan into Khyber Pakhtunkhwa , Pakistan , and forms a natural border between the two areas. Its highest peak is Mount Sikaram on the Afghanistan–Pakistan border , which towers above all surrounding hills to 4,755 m (15,600 ft) above mean sea level . The lower hills are mostly barren and treeless, but pine grows on

272-661: The 300 million years-long Huronian glaciation (during the Siderian and Rhyacian periods of the Paleoproterozoic) and the hypothesized Snowball Earth (during the Cryogenian period in the late Neoproterozoic); and the Ediacaran period (635–538.8  Ma ), which is characterized by the evolution of abundant soft-bodied multicellular organisms such as sponges , algae , cnidarians , bilaterians and

306-737: The Neoproterozoic Era at the end of the Proterozoic Eon, possibly climaxing with the hypothesized Snowball Earth of the Sturtian and Marinoan glaciations. One of the most important events of the Proterozoic was the accumulation of oxygen in the Earth's atmosphere. Though oxygen is believed to have been released by photosynthesis as far back as the Archean Eon, it could not build up to any significant degree until mineral sinks of unoxidized sulfur and iron had been exhausted. Until roughly 2.3 billion years ago, oxygen

340-690: The Pakistani side with the Aryob Valley of Paktia Province , Afghanistan. The most viable route over the main ridge of the White Mountains is the Agam Pass (3586 m), over which the distance from Jalalabad to Parachinar is 92 km. The Durand Line border formed in 1893 between Afghanistan and British India cuts through these mountains. According to US military intelligence, many al-Qaeda fighters, including Osama bin Laden , crossed

374-592: The Palaeoproterozoic or Mesoproterozoic, according to molecular data. Classically, the boundary between the Proterozoic and the Phanerozoic eons was set at the base of the Cambrian Period when the first fossils of animals, including trilobites and archeocyathids , as well as the animal-like Caveasphaera , appeared. In the second half of the 20th century, a number of fossil forms have been found in Proterozoic rocks, particularly in ones from

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408-516: The Spīn Ghar to escape to Pakistan during the Tora Bora offensive in 2001. Bin Laden hid in the sparsely vegetated mountains in the northern part, called Tora Bora . After 2004, the Spīn Ghar mountain range was a pivotal place and theater of many battles fought between the foreign fighters of al-Qaeda and the joint Northern Command of the Pakistani military , with the latter trying to prevent

442-808: The Takhti Khel Marwats , Bakkakhel Wazirs , and Miri and Barakzai Bannuchis. Kyber.org: Geography of Bannu and Environs 32°37′N 71°00′E  /  32.617°N 71.000°E  / 32.617; 71.000 This Khyber Pakhtunkhwa location article is a stub . You can help Misplaced Pages by expanding it . This article related to a river in Pakistan is a stub . You can help Misplaced Pages by expanding it . Sp%C4%ABn Ghar The Spīn Ghar ( Pashto : سپین غر ) or Safēd Kōh ( Dari : سفیدکوه , less used in this area) meaning both White Mountains , or sometimes ( Pashto : Selseleh-ye Safīd Kūh ) meaning white mountain range ,

476-486: The breakup of the supercontinent Columbia and prior to the assemblage of the supercontinent Gondwana (~500 Ma). The defining orogenic event associated with the formation of Gondwana was the collision of Africa, South America, Antarctica and Australia forming the Pan-African orogeny . Columbia was dominant in the early-mid Proterozoic and not much is known about continental assemblages before then. There are

510-522: The deciphering of Precambrian Supereon tectonics. It is known that tectonic processes of the Proterozoic Eon resemble greatly the evidence of tectonic activity, such as orogenic belts or ophiolite complexes, we see today. Hence, most geologists would conclude that the Earth was active at that time. It is also commonly accepted that during the Precambrian, the Earth went through several supercontinent breakup and rebuilding cycles ( Wilson cycle ). In

544-426: The eon continued the massive continental accretion that had begun late in the Archean Eon. The Proterozoic Eon also featured the first definitive supercontinent cycles and wholly modern mountain building activity ( orogeny ). There is evidence that the first known glaciations occurred during the Proterozoic. The first began shortly after the beginning of the Proterozoic Eon, and evidence of at least four during

578-735: The first half of the Ediacaran from 0.63–0.55 Ga, and the Belomorian, spanning from 0.55–0.542 Ga. The emergence of advanced single-celled eukaryotes began after the Oxygen Catastrophe . This may have been due to an increase in the oxidized nitrates that eukaryotes use, as opposed to cyanobacteria . It was also during the Proterozoic that the first symbiotic relationships between mitochondria (found in nearly all eukaryotes) and chloroplasts (found in plants and some protists only) and their hosts evolved. By

612-414: The foreign fighters' incursion into Pakistan. Proterozoic The Proterozoic ( IPA : / ˌ p r oʊ t ər ə ˈ z oʊ ɪ k , ˌ p r ɒ t -, - ər oʊ -, - t r ə -, - t r oʊ -/ PROH -tər-ə- ZOH -ik, PROT-, -⁠ər-oh-, -⁠trə-, -⁠troh- ) is the third of the four geologic eons of Earth's history , spanning the time interval from 2500 to 538.8   Mya ,

646-419: The formation of high grade metamorphism and therefore did not achieve the same levels of subduction as was occurring in the Proterozoic Eon. As a result of remelting of basaltic oceanic crust due to subduction, the cores of the first continents grew large enough to withstand the crustal recycling processes. The long-term tectonic stability of those cratons is why we find continental crust ranging up to

680-665: The late Palaeoproterozoic, eukaryotic organisms had become moderately biodiverse. The blossoming of eukaryotes such as acritarchs did not preclude the expansion of cyanobacteria – in fact, stromatolites reached their greatest abundance and diversity during the Proterozoic, peaking roughly 1.2 billion years ago. The earliest fossils possessing features typical of fungi date to the Paleoproterozoic Era, some 2.4 billion years ago; these multicellular benthic organisms had filamentous structures capable of anastomosis . The Viridiplantae evolved sometime in

714-625: The late Proterozoic (most recent), the dominant supercontinent was Rodinia (~1000–750 Ma). It consisted of a series of continents attached to a central craton that forms the core of the North American Continent called Laurentia . An example of an orogeny (mountain building processes) associated with the construction of Rodinia is the Grenville orogeny located in Eastern North America. Rodinia formed after

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748-657: The longest eon of the Earth's geologic time scale . It is preceded by the Archean and followed by the Phanerozoic , and is the most recent part of the Precambrian "supereon". The Proterozoic is subdivided into three geologic eras (from oldest to youngest): the Paleoproterozoic , Mesoproterozoic and Neoproterozoic . It covers the time from the appearance of free oxygen in Earth's atmosphere to just before

782-769: The main mountains that form the East Afghan montane conifer forests . The range extends from the Peshawar valley in the east about 160 kilometers west to the Logar valley in Afghanistan. The Kabul River cuts a narrow trough through the Spīn Ghar mountains to flow eastward into the Indus River . The range connects directly with the Shandur Top offshoot of the Hindu Kush mountain system. The highest peak

816-631: The nearly barren lower slopes, forests of pine and deodar cedar thrived on the main range, but devastation during the Afghan civil wars reduced timber resources. The valleys still support some agriculture. The rivers of the White Mountains serve the irrigation of the fields in the densely populated river valleys, which allows the pelvis of Jalalabad multiple harvests. Wheat, maize, various types of vegetables (onions, green beans, okra, tomatoes, etc.), cotton, opium poppies, lemons, sugar cane, and olives are also grown around Jalalabad. The Bara high valley in

850-566: The proliferation of complex life on the Earth during the Cambrian Explosion . The name Proterozoic combines two words of Greek origin: protero- meaning "former, earlier", and -zoic , meaning "of life". Well-identified events of this eon were the transition to an oxygenated atmosphere during the Paleoproterozoic; the evolution of eukaryotes via symbiogenesis ; several global glaciations , which produced

884-554: The sessile Ediacaran biota (some of which had evolved sexual reproduction ) and provides the first obvious fossil evidence of life on Earth . The geologic record of the Proterozoic Eon is more complete than that for the preceding Archean Eon. In contrast to the deep-water deposits of the Archean, the Proterozoic features many strata that were laid down in extensive shallow epicontinental seas ; furthermore, many of those rocks are less metamorphosed than Archean rocks, and many are unaltered. Studies of these rocks have shown that

918-419: The southeast of the range is one of the most intensively used agricultural areas of the Pakistani tribal areas under Khyber Pakhtunkhwa . Older reports speak of rich orchards in the valleys of Spīn Ghar with mulberry and pomegranate trees. Wood from the eastern Afghan forests has been exported mainly to Pakistan since the 19th century, and in increasingly irresponsible quantities, so that Afghanistan imposed

952-468: The summit there are cirque glaciers, some of which are filled with scree. On the southern flank of the Sikaram Sar follow from 2500 m from bottom to top: alluvial soils in valleys, limestone and dolomite up to 4000 m, an intermediate zone of slate at 4000 m, above crystalline rock. A 20,000 hectare biotope in the southwest of Spīn Ghar is listed as an important bird area in Afghanistan. Above

986-567: The time was virtually all obligate anaerobic . A second, later surge in oxygen concentrations is called the Neoproterozoic Oxygenation Event , occurred during the Middle and Late Neoproterozoic and drove the rapid evolution of multicellular life towards the end of the era. The Proterozoic Eon was a very tectonically active period in the Earth's history. The late Archean Eon to Early Proterozoic Eon corresponds to

1020-577: The west; and Khost , and Parachinar in Pakistan to the south. The range between Herat in the west and Chaghcharan in the east is called Paropamisus Mountains . The White Mountains are part of the western rim that separates the Indian subcontinent from the Eurasian Plate . The base of the mountains consists of Proterozoic gneisses and granites with admixtures of gabbros , mafic metavolcanic rocks , marble and migmatites . On

1054-444: Was determined that there were several episodes of rapid increase in continental crust production. The reason for these pulses is unknown, but they seemed to have decreased in magnitude after every period. Evidence of collision and rifting between continents raises the question as to what exactly were the movements of the Archean cratons composing Proterozoic continents. Paleomagnetic and geochronological dating mechanisms have allowed

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1088-511: Was probably due to two factors: Exhaustion of the chemical sinks, and an increase in carbon sequestration , which sequestered organic compounds that would have otherwise been oxidized by the atmosphere. The first surge in atmospheric oxygen at the beginning of the Proterozoic is called the Great Oxygenation Event , or alternately the Oxygen Catastrophe – to reflect the mass extinction of almost all life on Earth, which at

1122-487: Was probably only 1% to 2% of its current level. The banded iron formations , which provide most of the world's iron ore , are one mark of that mineral sink process. Their accumulation ceased after 1.9 billion years ago, after the iron in the oceans had all been oxidized . Red beds , which are colored by hematite , indicate an increase in atmospheric oxygen 2 billion years ago. Such massive iron oxide formations are not found in older rocks. The oxygen buildup

1156-761: Was the Labradorian, lasting from 2.0–1.65  Ga . It was followed by the Anabarian, which lasted from 1.65–1.2 Ga and was itself followed by the Turukhanian from 1.2–1.03 Ga. The Turukhanian was succeeded by the Uchuromayan, lasting from 1.03–0.85 Ga, which was in turn succeeded by the Yuzhnouralian, lasting from 0.85–0.63 Ga. The final two zones were the Amadeusian, spanning

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