Lacustrine plain

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A lacustrine plain or lake plain is a plain formed due to the past existence of a lake and its accompanying sediment accumulation. Lacustrine plains can be formed through one of three major mechanisms: glacial drainage, differential uplift, and inland lake creation and drainage. Lake plains can have various uses depending on where and how they form.

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Sediment deposition in Garfield County, Montana Sediment19 (25192118228).jpg
Sediment deposition in Garfield County, Montana

Over time, in regions where a lake once existed, as water drains or evaporates from the lake, the deposited sediments are left behind, resulting in a level plain of land where the lake once existed. The soil of the plain may constitute fertile and productive farmland due to the previous accumulation of lacustrine sediments; in other cases, it may become a wetland or a desert. [1]

Background

Lacustrine plains are plains formed when lakes filled with sediments are drained. There are several reasons why drainage might occur, but in all cases the water in the lake is lost, leaving behind a level land of sediments. The resulting plain is an area of flat land which is often rich in fine-grained sediments. Depending on geologic and climatic factors, the once-lake region may turn into a desert or wetland. In other cases, lacustrine plains may have agricultural value. [2]

Origins of lacustrine plains and their formation mechanisms

The origins of lacustrine plains are lakes formed under different circumstances. Lake plains resulting from the drainage of glacial lakes are called glaciolacustrine plains, which differ from those resulting from differential uplifts and those from the creation of inland lakes.

Glacial drainage

Glaciolacustrine plains form when the lakes in the continental ice sheets drain and leave the rocky debris within behind. The most recent ice age, the Wisconsin, was a drive for glacial lake formation and the glaciolacustrine plain formation that followed. [3] Glacial lakes are grouped into categories which represent the conditions in which they form. Lake formations depending on the existence of active glaciers are different from those depending on the proximity of the lake to glaciers and those depending on glacier retreats. Regardless of the difference in those glacial lakes' formation conditions, lakes that are trapped inside ice walls drain after the ice walls melt, and the sediments in the lakes form glaciolacustrine plains.

Examples of glaciolacustrine plain formations

Glaciolacustrine plain formations can be found in a variety of places. For instance, Lake Agassiz-Ojibway Basin in northwestern Quebec is a good example of lacustrine plain formation caused by the ice readvance and drainage of Lake Ojibway. By analyzing the varve sequences and dividing them into the Matagami section and La Reine section, researchers were able to determine the time of occurrence for a major ice readvance event in the area and two drainage events in the lake. It was concluded that two drainage events separated by approximately 65 years led to the final drainage of the lake and the formation of the glaciolacustrine Agassiz-Ojibway Basin. [4]

Other locations of glaciolacustrine plains include Lake Erie, Saginaw Bay in Lake Huron, and the Lake Superior lake plain.

Differential uplift

Lake plains caused by tectonic movements, or epeirogeny, constitute another type of lacustrine plain. Due to tectonic events, the uplift of crusts may occasionally lead to the formation of basins. Later, as water fill the region, a lake is formed. Various factors may contribute to the drainage of the lakes formed in such fashion, and the sediments form a large, flat plain where the lakes once existed. [3]

Examples of differential uplift lacustrine plain formations

Lacustrine plains formed by differential uplift can be found in multiple locations, and they are most commonly seen in Africa. The Nile drainage system, for example, is a drainage system formed by mantle plumes activity induced tectonic uplift, forming the Rwenzori and Virunga Mountains. [5] This uplift led to a segmentation of the west East African Rift System and led to the difference in flowing directions of the rivers in the northwestern Main Ethiopian Rift and the eastern and western East African Rift System. The regional tectonics therefore contributed to a redirection of the rivers, causing the Paleo-lake Obweruka to break into smaller regional lakes and the drainage system to change. [5]

Tectonics-induced lacustrine plain formation can also be found at the Congo Lake Plain and the Lake Plain of South Sudan.

Inland lake creation and drainage

While differential uplift can certainly create inland basins and lakes, many inland lakes are created due to a period of heavy and consistent rainfall that the region experiences. Like any other lake, lakes formed in inland basins are bound to face obliteration. As sediments deposit and accumulate at the bottom of the lake and as water drains due to environmental forces and geologic events, the lake gradually approaches its full state. A lacustrine plain is then formed when drainage reaches completion, and the lake becomes a plain of sediments. [3]

Examples of inland lake creation and drainage

One example of inland lake creation in once arid land is Lake Eyre in South Australia. The Lake Eyre North basin formed due to tectonic subsidence, and repeating glacial cycles and climatic cycles led to wet and dry cycles in the lake where the state of the lake changed drastically. [6] Lake Eyre is currently a playa, indicating that it is in a relatively arid episode. However, it was much wetter when it was in flood-dominated episodes, and it held more water than its current ephemeral state. [6]

The Chad Basin Plain is also a good example of inland lacustrine plain formation. By conducting facies analysis, researchers are able to determine four lithofacies associations for the Chad Basin, and thus the sequences of the Chad Basin's formation. [7] Those lithofacies with little plant debris indicate a period of aridity and represent the last sequence of Chad formation where a lacustrine plain existed. [7]

Other examples of inland lake creation, drainage, and lake plain formation can be found at plains near the Caspian Sea and the Lake Bonneville Plain.

The value of lacustrine plains

Agriculture value

The Great Plains in North America are examples of the agricultural values of lacustrine plains. The flat lake plain where Lake Agassiz once lied now serves as a cropland for sugar beets and potatoes. [8] Beneficial to the growth of the crops, the soils of the lacustrine plains in the Great Lakes region are fertile due to prior sedimentation, and the land is so flat that crops can thrive. The remaining glacial materials also provide essential nutrients for crop growth and thus boost farm productivity. [8]

Paleoenvironmental reconstruction value

Lacustrine plains are also valuable in paleoenvironment and paleoclimate studies. By surveying the western lake plain of Llancanelo Lake in Argentina, researchers were able to gather geomorphological data and sedimentary evidence to reconstruct the extension of the lake in the past. It was concluded that the lake extended a larger territory in the past. [9] In the case of Llancanelo Lake, the western lacustrine plain was a crucial factor in determining the evolution of the lake. A similar use of drainage areas and lacustrine plain can be found in a research done on the Congo. Sedimentation and drainage data collected through monitoring the Congo's drainage system provide valuable insight into the glacial stages and climate periods the region has gone through. [10]  

See also

Related Research Articles

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<span class="mw-page-title-main">Lake Agassiz</span> Large lake in central North America at the end of the last glacial period

Lake Agassiz was a large proglacial lake that existed in central North America during late Pleistocene, fed by meltwater from the retreating Laurentide Ice Sheet at the end of the last glacial period. At its peak, the lake's area was larger than all of the modern Great Lakes combined.

Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.

<span class="mw-page-title-main">Endorheic basin</span> Closed drainage basin that allows no outflow

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<span class="mw-page-title-main">Interior Plains</span> Physiographic and geologic region of the United States and Canada

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<span class="mw-page-title-main">Terrace (geology)</span> A step-like landform

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<span class="mw-page-title-main">Knickpoint</span> Point on a streams profile where a sudden change in stream gradient occurs

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<span class="mw-page-title-main">Passive margin</span> Transition between oceanic and continental lithosphere that is not an active plate margin

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<span class="mw-page-title-main">Lake Maumee</span> Former lake in North America

Lake Maumee was a proglacial lake and an ancestor of present-day Lake Erie. It formed about 17,500 calendar years, or 14,000 Radiocarbon Years Before Present (RCYBP) as the Huron-Erie Lobe of the Laurentide Ice Sheet retreated at the end of the Wisconsin glaciation. As water levels continued to rise the lake evolved into Lake Arkona and then Lake Whittlesey.

<span class="mw-page-title-main">Proglacial lakes of Minnesota</span>

The proglacial lakes of Minnesota were lakes created in what is now the U.S. state of Minnesota in central North America in the waning years of the last glacial period. As the Laurentide Ice Sheet decayed at the end of the Wisconsin glaciation, lakes were created in depressions or behind moraines left by the glaciers. Evidence for these lakes is provided by low relief topography and glaciolacustrine sedimentary deposits. Not all contemporaneous, these glacial lakes drained after the retreat of the lobes of the ice sheets that blocked their outlets, or whose meltwaters fed them. There were a number of large lakes, one of which, Glacial Lake Agassiz, was the largest body of freshwater known to have existed on the North American continent; there were also dozens of smaller and more transitory lakes filled from glacial meltwater, which shrank or dried as the ice sheet retreated north.

<span class="mw-page-title-main">Drainage system (geomorphology)</span> Patterns formed by streams, rivers, and lakes in a drainage system

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<span class="mw-page-title-main">Lake</span> Large body of relatively still water

A lake is a naturally occurring, relatively large body of water localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from the ocean, although, like the much larger oceans, they form part of the Earth's water cycle by serving as large standing pools of storage water. Most lakes are freshwater and account for almost all the world's surface freshwater, but some are salt lakes with salinities even higher than that of seawater.

<span class="mw-page-title-main">Ancient lake</span> Lakes at least one million years old

An ancient lake is a lake that has consistently carried water for more than one million years. 12 of the 20 ancient lakes have existed for more than 2.6 million years, the full Quaternary period. Ancient lakes continue to persist due to plate tectonics in an active rift zone. This active rift zone creates lakes that are extremely deep and difficult to naturally fill with sediment. Due to the prolonged life of ancient lakes, they serve as models for isolated evolutionary traits and speciation. Most of the world's bodies of water are less than 18,000 years old. There are only 20 ancient lakes over 1 million years old.

<span class="mw-page-title-main">Lacustrine deposits</span>

Lacustrine deposits are sedimentary rock formations which formed in the bottom of ancient lakes. A common characteristic of lacustrine deposits is that a river or stream channel has carried sediment into the basin. Lacustrine deposits form in all lake types including rift graben lakes, oxbow lakes, glacial lakes, and crater lakes. Lacustrine environments, like seas, are large bodies of water. They share similar sedimentary deposits which are mainly composed of low-energy particle sizes. Lacustrine deposits are typically very well sorted with highly laminated beds of silts, clays, and occasionally carbonates. In regards to geologic time, lakes are temporary and once they no longer receive water, they dry up and leave a formation.

<span class="mw-page-title-main">Lake Atna</span> Prehistoric lake in Alaska

Lake Atna was a prehistoric proglacial lake that initially formed approximately 58 ka in the Copper River Basin, an area roughly centered around 245 km (152 mi) northeast of modern-day Anchorage, Alaska. The lake formed, and dispersed, during the Wisconsin glaciation. The lake existed in several forms, with several prominent shorelines observable in modern geology. At its greatest extent, the lake surface area was approximately half the size of modern-day Lake Ontario, and possibly much larger. The basin of the lake lay within an area bordered by the Alaska Range to the north, the Wrangell Mountains to the east, the Chugach Mountains to the south, and the Talkeetna Mountains to the west.

<span class="mw-page-title-main">Junggar Basin</span> Sedimentary basin in Xinjiang, China

The Junggar Basin, also known as the Dzungarian Basin or Zungarian Basin, is one of the largest sedimentary basins in Northwest China. It is located in Dzungaria in northern Xinjiang, and enclosed by the Tarbagatai Mountains of Kazakhstan in the northwest, the Altai Mountains of Mongolia in the northeast, and the Heavenly Mountains in the south. The geology of Junggar Basin mainly consists of sedimentary rocks underlain by igneous and metamorphic basement rocks. The basement of the basin was largely formed during the development of the Pangea supercontinent during complex tectonic events from Precambrian to late Paleozoic time. The basin developed as a series of foreland basins – in other words, basins developing immediately in front of growing mountain ranges – from Permian time to the Quaternary period. The basin's preserved sedimentary records show that the climate during the Mesozoic era was marked by a transition from humid to arid conditions as monsoonal climatic effects waned. The Junggar basin is rich in geological resources due to effects of volcanism and sedimentary deposition. According to Guinness World Records it is a land location remotest from open sea with great-circle distance of 2,648 km from the nearest open sea at 46°16′8″N86°40′2″E.

<span class="mw-page-title-main">Lake Alamosa</span> Former lake in Colorado, United States

Lake Alamosa is a former lake in Colorado. It existed from the Pliocene to the middle Pleistocene in the San Luis Valley, fed by glacial meltwater from surrounding mountain ranges. Water levels waxed and waned with the glacial stages until at highstand the lake reached an elevation of 2,335 meters (7,661 ft) and probably a surface of over 4,000 square kilometers (1,500 sq mi), but only sparse remains of the former waterbody are visible today. The existence of the lake was postulated in the early 19th century and eventually proven in the early 20th century.

References

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