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The geology of Laos includes poorly defined oldest rocks. Marine conditions persisted for much of the Paleozoic and parts of the Mesozoic, followed by periods of uplift and erosion. The country has extensive salt, gypsum and potash, but very little hydrocarbons and limited base metals. [1]
The Precambrian and Paleozoic are poorly attested in the Laotian rock record. Some areas in the northwest, northeast and southeast are believed to have high-grade metamorphic rocks from the Proterozoic. No Cambrian rocks have been verified, although some may be represented by metasedimentary rocks underlying Ordovician strata. Shale with graptolite fossils in the northeast belong to the Early Ordovician. Marines sedimentation took place during the Ordovician, Silurian and Devonian. Continuous sedimentation went on in the east into the Carboniferous, but elsewhere a marine regression brought erosion. The Permian and Carboniferous brought renewed marine deposition of sandstone, shale and limestone as well as some terrestrial deposits like coal found near Vientiane and Saravane. The limestone forms a prominent karst topography in the north and east.
Marine sedimentation only continued in a few sedimentary basins during the Triassic at the start of the Mesozoic, such as the Sam Neua area. Volcanic rocks that erupted primarily in the Permian, but into the Triassic are situated in northern Laos in the Pak Lay-Luang Prabang area and northwest to the border with Myanmar. They correlate with similar rocks in Thailand inferred to be the result of subduction-related volcanism. Dacite and rhyolite are common in the Sam Neua area while rhyolite and tuff covers much of the Sekong Valley and along the Cambodian border in the south.
Almost all Jurassic and Cretaceous rocks are terrestrial, except for marine rocks in the southern Sekong Valley from the Early Jurassic. A mountainous terrane formed due to Triassic uplift, which brought intense erosion. By the Middle Cretaceous, the land surface was heavily worn down leaving silt, clay and mud interspersed with evaporites, which underlie the plains around Vientiane and east of Savannakhet.
Paleogene deposits from the Cenozoic are absent in Laos, but Neogene freshwater sediments settled in small valleys between mountain ranges, made up of shale, sandstone, marl and lignite. Because of a lack of coarse sediments which typically erode off of steep neighboring mountains, geologists have interpreted these basins as the down-dropped remnants of older, wider basins. Highlands uplifted during the Pliocene and Pleistocene and immediately experienced intense erosion. The Plain of Jars has extensive gravel and silt terraces from the Quaternary, including loess and volcanic ash. The Mekong River which transported the eroded material may have followed a different course because sediments are primarily shallow and Holocene in age beneath the present course of the river. Thick basalt lavas extruded onto Mesozoic sandstone at the Bolovens Plateau east of Pakse during the Pleistocene. [2]
The Truong Son and Luang Prabang structures converge in northern Laos, bordered by northwest trending fault-bounded structures such as Phu Hoat Massif. The Song Ma Anticlinorium near Vietnam exposes Proterozoic basement rock at the surface. The Yunnan-Malay fold belt originated from closure of two sedimentary basins and is a prominent feature. Only a few major intrusions are known such as Early Triassic granodiorite near Pak Lay and gabbro near Sayaboury.
Laos has small amounts of tin, gypsum, limestone and coal and previously has alluvial sapphire, copper and salt mining. The country has extensive salt and gypsum deposits as well as potash near Vientiane, possible bauxite on the Bolovens Plateau and some iron deposits. Laterite deposits contain some cassiterite. [3]
The Llano Uplift is a geologically ancient, low geologic dome that is about 90 miles (140 km) in diameter and located mostly in Llano, Mason, San Saba, Gillespie, and Blanco counties, Texas. It consists of an island-like exposure of Precambrian igneous and metamorphic rocks surrounded by outcrops of Paleozoic and Cretaceous sedimentary strata. At their widest, the exposed Precambrian rocks extend about 65 miles (105 km) westward from the valley of the Colorado River and beneath a broad, gentle topographic basin drained by the Llano River. The subdued topographic basin is underlain by Precambrian rocks and bordered by a discontinuous rim of flat-topped hills. These hills are the dissected edge of the Edwards Plateau, which consist of overlying Cretaceous sedimentary strata. Within this basin and along its margin are down-faulted blocks and erosional remnants of Paleozoic strata which form prominent hills.
The Pyrenees are a 430-kilometre-long, roughly east–west striking, intracontinental mountain chain that divide France, Spain, and Andorra. The belt has an extended, polycyclic geological evolution dating back to the Precambrian. The chain's present configuration is due to the collision between the microcontinent Iberia and the southwestern promontory of the European Plate. The two continents were approaching each other since the onset of the Upper Cretaceous (Albian/Cenomanian) about 100 million years ago and were consequently colliding during the Paleogene (Eocene/Oligocene) 55 to 25 million years ago. After its uplift, the chain experienced intense erosion and isostatic readjustments. A cross-section through the chain shows an asymmetric flower-like structure with steeper dips on the French side. The Pyrenees are not solely the result of compressional forces, but also show an important sinistral shearing.
The geology of Germany is heavily influenced by several phases of orogeny in the Paleozoic and the Cenozoic, by sedimentation in shelf seas and epicontinental seas and on plains in the Permian and Mesozoic as well as by the Quaternary glaciations.
The geology of Georgia is the study of rocks, minerals, water, landforms and geologic history in Georgia. The country is dominated by the Caucasus Mountains at the junction of the Eurasian Plate and the Afro-Arabian Plate, and rock units from the Mesozoic and Cenozoic are particularly prevalent. For much of its geologic history, until the uplift of the Caucasus, Georgia was submerged by marine transgression events. Geologic research for 150 years by Georgian and Russian geologists has shed significant light on the region and since the 1970s has been augmented with the understanding of plate tectonics.
The geology of Moldova encompasses basement rocks from the Precambrian dating back more than 2.5 billion years, overlain by thick sequences of Proterozoic, Paleozoic, Mesozoic and Cenozoic sedimentary rocks.
The geology of Wyoming includes some of the oldest Archean rocks in North America, overlain by thick marine and terrestrial sediments formed during the Paleozoic, Mesozoic and Cenozoic, including oil, gas and coal deposits. Throughout its geologic history, Wyoming has been uplifted several times during the formation of the Rocky Mountains, which produced complicated faulting that traps hydrocarbons.
The geology of Utah, in the western United States, includes rocks formed at the edge of the proto-North American continent during the Precambrian. A shallow marine sedimentary environment covered the region for much of the Paleozoic and Mesozoic, followed by dryland conditions, volcanism, and the formation of the basin and range terrain in the Cenozoic.
The geology of the State of New York is made up of ancient Precambrian crystalline basement rock, forming the Adirondack Mountains and the bedrock of much of the state. These rocks experienced numerous deformations during mountain building events and much of the region was flooded by shallow seas depositing thick sequences of sedimentary rock during the Paleozoic. Fewer rocks have deposited since the Mesozoic as several kilometers of rock have eroded into the continental shelf and Atlantic coastal plain, although volcanic and sedimentary rocks in the Newark Basin are a prominent fossil-bearing feature near New York City from the Mesozoic rifting of the supercontinent Pangea.
The geology of Kazakhstan includes extensive basement rocks from the Precambrian and widespread Paleozoic rocks, as well as sediments formed in rift basins during the Mesozoic.
The geology of Afghanistan includes nearly one billion year old rocks from the Precambrian. The region experienced widespread marine transgressions and deposition during the Paleozoic and Mesozoic, that continued into the Cenozoic with the uplift of the Hindu Kush mountains.
The geology of Kyrgyzstan began to form during the Proterozoic. The country has experienced long-running uplift events, forming the Tian Shan mountains and large, sediment filled basins.
The geology of Uzbekistan consists of two microcontinents and the remnants of oceanic crust, which fused together into a tectonically complex but resource rich land mass during the Paleozoic, before becoming draped in thick, primarily marine sedimentary units.
The geology of Thailand includes deep crystalline metamorphic basement rocks, overlain by extensive sandstone, limestone, turbidites and some volcanic rocks. The region experienced complicated tectonics during the Paleozoic, long-running shallow water conditions and then renewed uplift and erosion in the past several million years ago.
The geology of North Korea has been studied by the Central Geological Survey of Mineral Resources, rare international research and by inference from South Korea's geology.
The geology of Bulgaria consists of two major structural features. The Rhodope Massif in southern Bulgaria is made up of Archean, Proterozoic and Cambrian rocks and is a sub-province of the Thracian-Anatolian polymetallic province. It has dropped down, faulted basins filled with Cenozoic sediments and volcanic rocks. The Moesian Platform to the north extends into Romania and has Paleozoic rocks covered by rocks from the Mesozoic, typically buried by thick Danube River valley Quaternary sediments. In places, the Moesian Platform has small oil and gas fields. Bulgaria is a country in southeastern Europe. It is bordered by Romania to the north, Serbia and North Macedonia to the west, Greece and Turkey to the south, and the Black Sea to the east.
The geology of Slovakia is structurally complex, with a highly varied array of mountain ranges and belts largely formed during the Paleozoic, Mesozoic and Cenozoic eras.
Geology of Latvia includes an ancient Archean and Proterozoic crystalline basement overlain with Neoproterozoic volcanic rocks and numerous sedimentary rock sequences from the Paleozoic, some from the Mesozoic and many from the recent Quaternary past. Latvia is a country in the Baltic region of Northern Europe.
The geology of Greece is highly structurally complex due to its position at the junction between the European and African tectonic plates.
The geology of Denmark includes 12 kilometers of unmetamorphosed sediments lying atop the Precambrian Fennoscandian Shield, the Norwegian-Scottish Caledonides and buried North German-Polish Caledonides. The stable Fennoscandian Shield formed from 1.45 billion years ago to 850 million years ago in the Proterozoic. The Fennoscandian Border Zone is a large fault, bounding the deep basement rock of the Danish Basin—a trough between the Border Zone and the Ringkobing-Fyn High. The Sorgenfrei-Tornquist Zone is a fault-bounded area displaying Cretaceous-Cenozoic inversion.
The geology of Yukon includes sections of ancient Precambrian Proterozoic rock from the western edge of the proto-North American continent Laurentia, with several different island arc terranes added through the Paleozoic, Mesozoic and Cenozoic, driving volcanism, pluton formation and sedimentation.
