Geology of Farmington Hills, Michigan

Farmington Hills is a city in southeastern Michigan, located in western Oakland County. With a population of over 80,000 residents, Farmington Hills is a major suburb of Detroit. The geology of Farmington Hills reflects the region’s position on the Canadian Shield, with ancient Precambrian bedrock underlying more recent glacial deposits from the Pleistocene Ice Age. This article will provide an overview of the key geological features and history that have shaped Farmington Hills’ landscape.

Bedrock Geology

The bedrock geology of Farmington Hills consists of Precambrian igneous and metamorphic rocks which are over one billion years old. These ancient basement rocks belong to the Midcontinent Rift System, a large geological province that covers the Great Lakes region.

Metavolcanic Rocks

A significant portion of Farmington Hills sits atop metavolcanic rocks that are part of the Penokean Volcanic Belt. These rocks originated as volcanic flows and ash deposits that were later metamorphosed by heat and pressure deep below the surface. They typically consist of metarhyolites and meta-andesites.

Granite & Rhyolite

Bands of granite and rhyolitic intrusions dating to 1.1 billion years ago also underlie parts of Farmington Hills. These formed from molten magma that cooled slowly below the surface. They comprise igneous basement rock that crystallized deep underground.

Gneiss & Schist

Other common bedrock types include gneiss and schist. Gneiss formed as granitic rocks were subjected to high temperatures and pressures, causing the minerals to realign. Schist is a metamorphic rock with strong foliation or banding along mineral grains. Both contain important clues about the extreme forces that shaped the continent over geologic time.

Glacial Geology & Deposits

The bedrock geology of Farmington Hills is largely obscured by more recent glacial deposits laid down during the Pleistocene Ice Age. Massive continental glaciers repeatedly advanced over Michigan, scouring the landscape and leaving thick deposits of sediment.

Glacial Till

The most widespread glacial deposit is till, a mixture of clay, sand, gravel and boulders directly released from melting glaciers. Till covers the bedrock surface across most of Farmington Hills and can reach 100 feet in thickness. The till contains a wide diversity of rock types picked up by glaciers advancing from different directions.

Outwash & Ice-Contact Deposits

Meltwater from the glaciers also washed sediment into outwash plains, deltas, kames and eskers. These stratified deposits often form more permeable aquifers compared to till. They mainly occur along the major river valleys.

Glacial Lakes & Lacustrine Sediments

Several temporary lakes formed during the retreat of the glaciers, leaving fine lacustrine deposits of clay, silt and sand. These lakebed sediments are found in low-lying and marshy areas.

Loess

A blanket of loess, an eolian silt deposited after glaciation by winds, covers parts of the landscape. Loess gives the soils a characteristic sandy texture.

Post-Glacial Geology

The retreat of glaciers kickstarted other geological processes that continue to shape the landscape today.

Rivers & Streams

Rivers and streams eroded channels into the glacial sediments across Farmington Hills. Alluvium containing sand, gravel and boulders accumulates along riverbeds. Major drainage systems include the Rouge River watershed.

Geology of Wetlands & Lakes

Kettle lakes, ponds and wetlands dot the terrain, including features like Quarternary Lake. Organic muck and peat deposits accumulate in these depressed areas. New wetlands also form where glacial soils compact or dissolve to create depressions.

Mass Wasting

Steep slopes created by glacial till and outwash are prone to mass wasting processes like slumping. Talus deposits accumulate at the base of steeper bluffs and ravines.

Karst Features

Dissolution of subsurface carbonates has created karst topography in places, with sinkholes, caves and springs. These features channel and store groundwater.

Soils

Diverse soil types have developed across Farmington Hills based on the underlying geology. Sandy loams formed in glacial outwash tend to have the highest agricultural productivity. Clay-rich tills make less favorable soils.

Economic Geology

Farmington Hill’s geological resources have been utilized for economic purposes since Native American settlement.

Crushed Stone Aggregates

Sand, gravel and crushed stone left by glacial deposits provide a key economic resource, widely mined for construction aggregate. Pit mines are excavated wherever substantial glacial sediments occur.

Groundwater

Glacial outwash and ice-contact sediments provide important aquifers for municipal groundwater. Wells tap permeable subsurface layers of sand and gravel that can yield abundant fresh water. However, overuse depletes some aquifers.

Conclusion

In summary, Farmington Hill’s landscape reflects the imprint of continental glaciation across underlying Precambrian shield rocks. This geological foundation spawned the hills, valleys, lakes and wetlands that shaped both the ecology and human settlement patterns of the region. Ongoing geological processes continue to modify the terrain. Wise stewardship of the city’s geological resources and hazards provides an important key to sustainable development.