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. [1] Latvia is a country in the Baltic region of Northern Europe.
Several hundred boreholes have returned data about the Precambrian crystalline basement of Latvia, indicating young Middle Proterozoic intrusive rocks such as 1.65 billion year old rapakivi granite or 1.82 billion year old granodiorite in the northeast. Most basement probably formed before the Svecofennian orogeny, between the Archean and Proterozoic.
The Valmiera-Lokno Rise has early Archean amphibolite, gneiss, granitoid and migmatite under the east of Latvia, although metavolcanics, granulite gneiss and magnetite-bearing quartzite are most common in the Riga Megablock. The Garsene-Limbazi megablock has steeply dipping amphibolite, epidote amphibolite, plagiogneiss, migmatite granite, magnetite-rich quartzite (in the south) from the Proterozoic. Low-grade metavolcanics and 1.8 billion year old granodiorites cover the Riga Megablock in the Adazi assemblage. The Riga Pluton (or Kurzeme Pluton) is a large intrusion from 1.65 billion years ago with gabbro, anorthosite and rapakivi granite, covered in unmetamorphosed Pavilosta Formation volcanics along the west coast.
Mesoproterozoic rocks are separated from the Neoproterozoic by an erosion horizon. In western Latvia, basalt, gabbro-norite dikes, tuff, sand and gravel (sediments in the Zuru beds), limburgite and basaltic picrate are particularly common. The Valdai Group holds extensive siltstone, sandstone and clay from the Neoproterozoic. [2]
Cambrian rocks trace the Precambrian subsurface and the oldest, 50 to 130 meters thick are found in the east, including shale, argillite and sandstone. Fossil evidence indicates they correlate with the Cambrian Blue Shale in Estonia, early and middle Cambrian rocks in the west are about 220 meters thick. Upper parts of the lower section have brown oolite iron ore in argillite with a thickness of up to five meters and some rocks in the west host small amounts of oil.
Except in the north-center of the country, Ordovician rocks are everywhere in the subsurface and include argillite, shale and limestone about 250 meters thick at an average depth of 1.7 kilometers below sea level.
A disconformity separates Silurian rocks from Ordovician rocks and they are common in the subsurface, about 950 meters deep in the west or 162 meters in the north. Most are carbonate rocks with 23 different known graptolite zones.
Since the late 19th century, researchers have often focused on widespread Devonian rocks up to 900 meters thick that often directly underlie Quaternary deposits and outcrop along streams. Early Devonian rocks are 250 meters thick including siltstone, shale, sandstone, clay and ostracoderm fossils. Middle Devonian rocks have a shift toward argillite and gypsum and gypsum is quarried in Salaspils-Sauriesli between Ogre and Riga. Famenninan Stage dolomite and siltstone is up to 140 meters thick, overlain by Frasnian dolomite, quarried in the east for us ceramics.
Carboniferous rocks are limited to the southwest, with Tournasian age dolomitic sandstone, dolomite, sandstone and siltstone 104 meters thick.
Permian rocks are also confined to the southwest, with a significant disconformity from underlying Carboniferous rocks. Permian rocks from the Kazanian are 35 meters thick with carbonate shale, dolomite, limestone and sandstone. [3]
Only small areas in the southwest have Triassic rocks, including 74 meters of carbonate clays, sandstone and siltstone. Jurassic rocks are also confined to the southwest and are thinner at only 27 meters and include clay, quartz sands, sandstone, lignite, and siltstone with foraminifera fossils. [4]
Cenozoic units are largely absent in Latvia, except from the past 2.5 million years of the Quaternary, which cover the entire country, except where wave erosion has stripped them away on the east-central shore of the Gulf of Riga (or in some river valleys). In buried valleys, these sediments can be up to 310 meters thick, although the average thickness is up to 20 meters in lowlands 40 to 60 meters in highlands. Between Cesis and Madona and in the Vidzeme Highland in south-central part of the country, thicknesses can reach up to 200 meters. The Latgale Formation includes Precambrian crystalline clasts and gray clay left over from the first Pleistocene glaciation. Zidini Formation interglacial lakebed sediments overlie the Latgale up to 23.5 meters thick.
The overlying Letiza Formation correlates with formations such as the Oka in Russia or Sangaste in Estonia, associated with the Elsterian glaciation and includes till atop Jurassic rock. Eight meters of lacustrine sediment in the Pulvernieki or marine clays in the Akmenrags Formation line up with the mid-Pleistocene Holsteinian glaciation. Along the Baltic coast, up to 60 meters of brackish sand—the Jurkalne Member—overlies the Akmenrags Formation. The Kurzeme Formation gray calcareous material is widespread, left from the most extensive period of glaciation. The last interglacial is marked by the Felicianova Formation alluvium, overlain by Baltic group sediments from the last glacial advance.
Glacial retreat and oscillation took place from 25,000 to 12,000 years ago, leaving the 90 meter Latvia Formation, including the Jelgava Member lacustrine deposits. Major spillways drained the landscape, emptying the Baltic Ice Lake which flooded much of the region. The Yoldia Sea, Ancillus Lake, Littorina Sea and Limnea Sea all existed during the early Holocene, leaving behind shoreline deposits. [5]
The geology of Western Sahara includes rock units dating back to the Archean more than two billion years old, although deposits of phosphorus formed in the Mesozoic and Cenozoic have helped to prompt the current Moroccan occupation of most of the country.
The geology of Liberia is largely extremely ancient rock formed between 3.5 billion and 539 million years ago in the Archean and the Neoproterozoic, with some rocks from the past 145 million years near the coast. The country has rich iron resources as well as some diamonds, gold and other minerals in ancient sediment formations weathered to higher concentrations by tropical rainfall.
The geology of Uganda extends back to the Archean and Proterozoic eons of the Precambrian, and much of the country is underlain by gneiss, argillite and other metamorphic rocks that are sometimes over 2.5 billion years old. Sedimentary rocks and new igneous and metamorphic units formed throughout the Proterozoic and the region was partially affected by the Pan-African orogeny and Snowball Earth events. Through the Mesozoic and Cenozoic, ancient basement rock has weathered into water-bearing saprolite and the region has experienced periods of volcanism and rift valley formation. The East Africa Rift gives rise to thick, more geologically recent sediment sequences and the country's numerous lakes. Uganda has extensive natural resources, particularly gold.
The geological history of Zambia begins in the Proterozoic eon of the Precambrian. The igneous and metamorphic basement rocks tend to be highly metamorphosed and may have formed earlier in the Archean, but heat and pressure has destroyed evidence of earlier conditions. Major sedimentary and metamorphic groups formed in the mid-Proterozoic, followed by a series of glaciations in the Neoproterozoic and much of the Paleozoic which deposited glacial conglomerate as well as other sediments to form the Katanga Supergroup and rift-related Karoo Supergroup. Basalt eruptions blanketed the Karoo Supergroup in the Mesozoic and Zambia shifted to coal and sandstone formation. Geologically recent windblown sands from the Kalahari Desert and alluvial deposits near rivers play an important role in the modern surficial geology of Zambia. The country has extensive natural resources, particularly copper, but also cobalt, emeralds, other gemstones, uranium and coal.
The geology of Nigeria formed beginning in the Archean and Proterozoic eons of the Precambrian. The country forms the Nigerian Province and more than half of its surface is igneous and metamorphic crystalline basement rock from the Precambrian. Between 2.9 billion and 500 million years ago, Nigeria was affected by three major orogeny mountain-building events and related igneous intrusions. Following the Pan-African orogeny, in the Cambrian at the time that multi-cellular life proliferated, Nigeria began to experience regional sedimentation and witnessed new igneous intrusions. By the Cretaceous period of the late Mesozoic, massive sedimentation was underway in different basins, due to a large marine transgression. By the Eocene, in the Cenozoic, the region returned to terrestrial conditions.
The geology of Estonia is the study of rocks, minerals, water, landforms and geologic history in Estonia. The crust is part of the East European Craton and formed beginning in the Paleoproterozoic nearly two billion years ago. Shallow marine environments predominated in Estonia, producing extensive natural resources from organic matter such as oil shale and phosphorite. The Mesozoic and much of the Cenozoic are not well-preserved in the rock record, although the glaciations during the Pleistocene buried deep valleys in sediment, rechanneled streams and left a landscape of extensive lakes and peat bogs.
The geology of Belarus began to form more than 2.5 billion years ago in the Precambrian, although many overlying sedimentary units deposited during the Paleozoic and the current Quaternary. Belarus is located in the eastern European plain. From east to west it covers about 650 kilometers while from north to south it covers about 560 kilometers, and the total area is about 207,600 square kilometers. It borders Poland in the north, Lithuania in the northwest, Latvia and Russia in the north, and Ukraine in the south. Belarus has a planar topography with a height of about 160 m above sea level. The highest elevation at 346 meters above sea level is Mt. Dzerzhinskaya, and the lowest point at the height of 80 m is in the Neman River valley.
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 Bosnia & Herzegovina is the study of rocks, minerals, water, landforms and geologic history in the country. The oldest rocks exposed at or near the surface date to the Paleozoic and the Precambrian geologic history of the region remains poorly understood. Complex assemblages of flysch, ophiolite, mélange and igneous plutons together with thick sedimentary units are a defining characteristic of the Dinaric Alps, also known as the Dinaride Mountains, which dominate much of the country's landscape.
The geology of Sweden is the regional study of rocks, minerals, tectonics, natural resources and groundwater in the country. The oldest rocks in Sweden date to more than 2.5 billion years ago in the Precambrian. Complex orogeny mountain building events and other tectonic occurrences built up extensive metamorphic crystalline basement rock that often contains valuable metal deposits throughout much of the country. Metamorphism continued into the Paleozoic after the Snowball Earth glaciation as the continent Baltica collided with an island arc and then the continent Laurentia. Sedimentary rocks are most common in southern Sweden with thick sequences from the last 250 million years underlying Malmö and older marine sedimentary rocks forming the surface of Gotland.
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 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 Montana includes thick sequences of Paleozoic, Mesozoic and Cenozoic sedimentary rocks overlying ancient Archean and Proterozoic crystalline basement rock. Eastern Montana has considerable oil and gas resources, while the uplifted Rocky Mountains in the west, which resulted from the Laramide orogeny and other tectonic events have locations with metal ore.
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 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 Lithuania consists of ancient Proterozoic basement rock overlain by thick sequences of Paleozoic, Mesozoic and Cenozoic marine sedimentary rocks, with some oil reserves, abundant limestone, dolomite, phosphorite and glauconite. Lithuania is a country in the Baltic region of northern-eastern Europe.
The geology of Newfoundland and Labrador includes basement rocks formed as part of the Grenville Province in the west and Labrador and the Avalonian microcontinent in the east. Extensive tectonic changes, metamorphism and volcanic activity have formed the region throughout Earth history.
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.
