A lacustrine plain or lake plain is a

plain In geography, a plain, commonly known as flatland, is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and ...

formed due to the past existence of a

lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...

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. 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

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 A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...

or a

desert A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the la ...

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.

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. 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. Other locations of glaciolacustrine plains include

Lake Erie Lake Erie ( ) is the fourth-largest lake by surface area of the five Great Lakes in North America and the eleventh-largest globally. It is the southernmost, shallowest, and smallest by volume of the Great Lakes and also has the shortest avera ...

, Saginaw Bay in Lake Huron, and the

Lake Superior Lake Superior is the largest freshwater lake in the world by surface areaThe Caspian Sea is the largest lake, but is saline, not freshwater. Lake Michigan–Huron has a larger combined surface area than Superior, but is normally considered tw ...

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.

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. 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. 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.

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. 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. 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. Those lithofacies with little plant debris indicate a period of aridity and represent the last sequence of Chad formation where a lacustrine plain existed. Other examples of inland lake creation, drainage, and lake plain formation can be found at plains near the

Caspian Sea The Caspian Sea is the world's largest inland body of water, described as the List of lakes by area, world's largest lake and usually referred to as a full-fledged sea. An endorheic basin, it lies between Europe and Asia: east of the Caucasus, ...

and the Lake Bonneville Plain.

The value of lacustrine plains

Agriculture value

The

Great Plains The Great Plains is a broad expanse of plain, flatland in North America. The region stretches east of the Rocky Mountains, much of it covered in prairie, steppe, and grassland. They are the western part of the Interior Plains, which include th ...

in North America are examples of the agricultural values of lacustrine plains. The flat lake plain where Lake Agassiz once existed now serves as a cropland for sugar beets and potatoes. 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.

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. 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.

References

{{DEFAULTSORT:Lacustrine Plain Lacustrine landforms Plains