MODERN SEDIMENTS, WATER, AND WETLANDS:  Includes features where recent geologic processes have been occurring.  Recent geologic
processes causing erosion and transportation of sediment by wave action (lakes) and currents (streams) have sorted materials and deposited them as
features, such as beaches and alluvial flood plains.   These features are Holocene (10,000 years ago until Present) in age and include lakes, streams,
wetlands, beaches, and flood plains.
Water:  Open water including lakes and streams.

Wetlands - Organic Sediment:  Partially decomposed plant material, silt, and clay; includes shallow lakes, marshes and peat.  Wetlands
can be observed throughout the county.
Colluvial Sediments:  Clay, silt, sand, and gravel with occasional cobbles and boulders.  The sediment is poorly sorted, however, it
has thin (< 6 inches) sorted beds of sand scattered throughout. Colluvium is deposited on the foot of steep slopes along the Minnesota
River Valley where till banks collapse and become slightly washed by sheetwash and alluvial processes.  This colluvial sediment overlies
glacial sand and gravel outwash and limestone bedrock.
Beach Sediments:  Fine, medium, and coarse sand with occasional gravel sized particles and layers.  The sediment is generally
well-sorted and well-rounded and is interpreted as sediments associated with modern lake shores.  These sediments can be found along
the beaches of Madison Lake in the northeastern corner of the county.
Flood Plain Sediments:  Silt, fine sand, coarse sand, gravel, and clay layers overlying coarser sand and gravel layers and lenses.
The sediment is generally moderately- to well-sorted and interpreted as alluvial overbank deposits.  Within this unit, coarser sediment
is typically found in abandoned channels, point bars, and river bars.  Examples of alluvial sediment exist within the county in and
around the Maple, Le Sueur, Cobb, Watonwan, and Blue Earth Rivers.
Minnesota River Valley Flood Plain Sediments/Glacial Outwash Sediments:  Quartz rich medium and coarse sands overlying sand 
and gravel sediments.  The sediment is well- to very well-sorted and interpreted as glaciofluvial outwash sediments overlain by modern
flood plain sediments of the Minnesota River.  Glacial River Warren (which drained Glacial Lake Agassiz) carried large amounts of
outwash, however, the modern day Minnesota River is only capable of carrying much finer sediment.

GLACIAL DRIFT:  Includes all material (clay, silt, sand, gravel, and boulders) that was transported by glaciers and deposited directly from the glacier,
from the ice as the glacier retreated, or by running water associated with the glacier.  The glacial drift, which covers almost all of Blue Earth County,
is Pleistocene (2.5 million to 10,000 years ago) in age.
Terrace Sediments:  Sand and gravel with occasional cobbles and boulders scattered throughout.  The sediment is generally rounded to
well-rounded and well- to very well-sorted.  The sediment is interpreted to have been deposited in large glacial outwash channels such
as the ones paralleling the Blue Earth and Minnesota Rivers.  Glacial River Warren (which drained Glacial Lake Agassiz) was responsible
for the deposition of the large terrace deposits on the banks of the modern Minnesota River.
Thin Terrace Sediments over Bedrock:  Thin sand and gravel with an occasional cobble or boulder overlying bedrock.  The sediment is 
generally rounded to well-rounded and well- to very well-sorted.  The sediment is interpreted to have been deposited on the bedrock
terraces as the erosive behavior of Glacial River Warren decreased, thus causing the sediment load to be deposited as terraces
paralleling the Minnesota River.
Ice Contact - Kame Sediments:  Stratified fine to coarse sand and gravel with occasional thin silt and clay layers and lenses.  The
sediment forms low mounds and is interpreted to have been deposited by superglacial streams in low places or holes on the surface of
the glacier or as ponded deposits on the surface or at the margin of stagnant ice.  These features (kames) can be found on the stagnant
ice moraine tills just southwest of Lake Crystal.
Ice Contact - Esker Sediments:  Stratified sand and gravel with a very thin till cap in some areas.  These esker features form long,
narrow, sinuous ridges composed of irregularly stratified sand and gravel due to incorporation of and later melting of ice blocks.  They
are interpreted to have formed by a subglacial stream flowing between ice walls or in an ice tunnel of the stagnant glacier, then left 
behind as the ice melted.  These esker features can be found on the stagnant ice moraine tills just southwest of Lake Crystal and in the
northwestern corner of the county.
Collapsed Channel Sediments:  Discontinuous and patchy, fine to coarse sand and gravel sediment with walls composed of till (unsorted
clay, silt, sand, gravel, cobbles, and boulders).  This sand and gravel sediment is all that remains of large outwash channels, where
superglacial meltwater once carried massive amounts of sand, gravel, and finer sediments.  The sediment has been cleaned out of the 
channels and is often deposited as a large delta where the channel intersected standing water (Glacial Lake Minnesota).  All that remains
is collapsed till with small remnants of sand and gravel.  An example of one of these channels can be seen in the southwestern corner of
the county where this stripped out channel once supplied sediment to a very large delta.  Outwash channels also formed as Glacial Lake
Minnesota was allowed to drain to the north after the ice retreated.  
Outwash Channel Sediments:  Fine to coarse sand and gravel with occasional cobble or small boulder layers.  The sediment is interpreted
to be derived from large meltwater channels that ran on, within, and/or underneath the retreating glacier.  These channels also formed
as the water from Glacial Lake Minnesota drained due to the retreat of the glacier; these channels carried smaller amounts of sand and
gravel.  Much of the sediment is collapsed and discontinuous due to melting, buried iceblocks, and deposition on top of the ice, however,
large gravel ridges are found within these channels, as in the northwestern corner of the county.
Glacial Lake Sediments:  Silt, clay, fine sand, and medium sand layers.  These sediments are typically deposited as thin layers with
alternating summer and winter components called varves.  The sediment is interpreted to be derived from suspended material brought by
meltwater streams into Glacial Lake Minnesota, which bordered the receding glacier, as well as from stagnant ice melting within the lake
plain.  The sediments are therefore coarser (sandier) towards the meltwater and sediment source (meltwater streams/deltas), becoming
finer (silt/clay) outward in deeper calm water.  These sediments can be found throughout the southern part of the county.  The locations
of the deltas suggest that the glacial lake was much smaller at one time.  
Glacial Lake Sediments over Deltaic Sediments:  Silt, clay, fine sand, and medium sand layers overlying stratified medium and coarse
sand and gravel with occasional layers of silt, fine sand, and cobbles.  These deltaic sediments were deposited as outwash channels
entered Glacial Lake Minnesota (when it was much smaller), however, as the lake levels and areal extent of the lake increased, the
deltaic sediment was covered be deeper water sediments (silts, clays, and sands).  These sediments can be found in the southwestern
part of the county.
Deltaic Sediments:  Stratified medium and coarse sand and gravel with occasional layers of silt, fine sand, and cobbles.  Sediment is
deposited in large fan shaped or triangular features, called deltas, as meltwater streams enter standing water.  These deltas are typically
very large in areal extent.  The sediment exhibits stratified layers that have been thrusted, collapsed, and faulted due to the incorporation
of ice blocks within the delta as well as the deltas being deposited on top of ice.  These deltas formed as outwash channels entered the
glacial lake now known as Glacial Lake Minnesota as well as smaller icewalled lakes on the glacier.  Several deltas can be observed
throughout the county.
Till:  Unsorted clay, silt, sand, gravel, cobbles, and boulders.  Different till units with different textural characteristics were found
within the county, however, for the purposes of this study they were not broken down in any detail.  There are several locations along the
Le Sueur River where multiple till units are exposed, sometimes with 1-15 feet of gravel between them.  The till is also exposed where
alluvial valleys have cut through the glaciolacustrine sediment and in collapsed channels.  Till is the dominant sediment in the
northwestern quarter of the county due to stagnation and ground moraines.

BEDROCK UNITS*:  The Oneota Dolomite (dolomitic limestone) and Jordan Sandstone (quartzose sandstone) Formations that are exposed on large 
benches along the Minnesota River Valley, where Glacial River Warren eroded through the overlying glacial materials, thus exposing the bedrock.  
The limestone bedrock (Oneota Dolomite) units found within Blue Earth County are Ordovician (500 to 440 million years ago) in age and the
sandstone bedrock (Jordan Sandstone) units are Cambrian (570 to 500 million years ago) in age.  Thin sand and gravel outwash sediments are
commonly found overlying these units.
Limestone:  Light brown, brownish gray to buff, fine- to medium-grained dolomitic limestone with a silt-sized dolomite matrix.  Thin to
thick bedded with variable color and texture both horizontally and vertically.  Some of the lower beds are thicker and very well
consolidated.  Frequently porous and cavernous - commonly lined with calcite crystals.  Chert nodules and fossils are common with
occasional stromatolitic texture.  
Limestone overlying Sandstone:  Thin light brown, brownish gray to buff, fine- to medium-grained dolomitic limestone with a silt-sized
dolomite matrix overlying white, yellowish to light-brownish tan, and buff colored medium to thick bedded, coarse- to medium-grained
quartzose sandstone to dolomitic sandstone.  The overlying limestone layers are typically less than 15 feet thick.  The upper 10-30
feet of the quartzose sandstone is well consolidated and interfingered or interlayered with the limestone.
Sandstone:  White, yellowish to light-brownish tan, and buff colored medium to thick bedded, coarse- to medium-grained quartzose
sandstone to dolomitic sandstone.  The upper unit contains alternating layers of quartzose sandstone, dolomitic limestone, and dolomitic
sandstone and grades downward to fairly pure quartzose sandstone, then into well consolidated sandstone, and finally into loosely
consolidated sandstone. The quartz purity of this unit increases downward until it is >95% pure quartz sandstone.  This unit could be
evaluated for industrial sand at depth. 

    *G.S. Austin, 1972, "Paleozoic Lithostratigraphy of Southeastern Minnesota", in Geology of Minnesota:  A Centennial Volume, Minnesota
    Geological Survey, P.K. Sims and G.B. Morey, eds., pp. 459-473.
