By Dr. Jack A. Sunderman
Most of the topographic features of Metea Park and the surrounding area (“Metea Park Region”) were produced about 20,000 to 10,000 years ago by
Wisconsinan continental glaciers and their meltwater streams. As the glaciers moved slowly through this area they melted constantly, depositing sediment both beneath the ice and around its margins, leaving gently rolling to hilly landforms. Meltwater streams issuing from the ice also produced landforms, including ice-marginal valleys, cross-moraine valleys and sluiceways filled or partly filled with sediment.
Glacial SedimentsTillSediment deposited directly from glaciers is called
till, or in the Midwest, clay till, much of which was derived from nearby sedimentary rocks. Clay till in this area was derived primarily from rocks of Silurian and Devonian age (420 million to 360 million years old) exposed between here and Lake Erie. Limestones, sandstones, and especially shales of this area were easily ground by the glaciers into calcareous sand, silt, and clay size sediment. Northern Indianan’s till also is calcareous, because it contains finely ground limestone, composed of
calcite (CaCO3).
However, as anyone who has attempted to dig into northern Indiana’s gray clay knows, pebbles and even large boulders also occur in the till. The larger rocks are of two origins, local and distant. Sedimentary blocks consist of relatively resistant rocks, mostly limestone derived from nearby sources in Indiana or Ohio.
The most exotic and interesting boulders are very resistant rocks derived from more distant sources, on the Canadian Shield. These sometimes beautiful specimens vary in composition from pink or gray granite (intrusive igneous origin) to white quartzite (metamorphic) or black basalt (volcanic igneous), and almost everything between. Some of these rocks have been rounded by interludes of stream transport, and others have been planed flat on one or more sides while in the grip of the ice.
These rocks have survived the long trip from Canada because they consist of interlocking crystals of hard minerals such as quartz and feldspars, making them resistant to weathering and abrasion. Other less resistant Canadian rocks, such as metamorphic gneiss (layered) and marble (soft), have been broken or ground to small sizes and thus seem less abundant than the other rocks.
The locations of these intriguing rocks, and even an occasional small diamond or fleck of gold, are not predictable. Glacial ice is a solid transporting agent that cannot sort sediment. Thus the Canadian rocks (and sparse gems) are randomly distributed throughout the till. Clay till has virtually no important economic use.
OutwashSediment deposited from glacial meltwater is called
outwash. It contains the same types of materials as till, but because meltwater streams are capable of sorting their sediment load, outwash typically consists of beds or lenses of sand and gravel; finer silt and clay sediments usually are carried in suspensions and transported farther downstream. In some areas, glacial outwash is a major economic resource of both sand and gravel.
Lake SedimentsNumerous glacial lakes were impounded between the ice and
moraines, or within moraines. Other lake basins were produced by partial burial and melting of blocks of glacial ice, forming so-called
kettle lakes. Lake James and some of the Chain-O-Lakes basins are thought to have this origin.
Fine silt and clay from glacial meltwater accumulated in the quiet waters of many glacial lakes. Greater melting and sedimentation during warm summer months produced layers of light-colored silty sediment, whereas lower rates of melting and sedimentation during winter months produced thinner and darker clay-rich layers. One couplet of light and dark sediment is called a varve, and represents one year’s accumulation. Varved lake sediments thus can be used to determine the length of time a glacial lake existed. Some small glacial lakes became the sites of peat bogs, eventually filling with plant material.
Landforms and Meltwater StreamsLake PlainsAlthough many glacial lakes still exist in the glaciated areas of northern Indiana, others have been drained, leaving very extensive and amazingly flat surfaces, or lake plains. Perhaps the most famous of these is the strikingly flat and enormously large lake plain of Glacial Lake Maumee and related glacial lakes; it extends from the Fort Wayne-New Haven area all the way to Lake Erie. This amazing lake-bottom surface really is a series of lake plains that formed stepwise across northwestern Ohio. As the front of the melting glacier receded through Ohio in a series of stages, the ponded meltwater first produced Lake Maumee, then other Ohio lakes at lower levels, and finally modern Lake Erie.
End MorainesThe most prominent landforms of the Metea Park Region are its end moraines, areas of hummocky or hilly topography formed by deposition of till at the margin of glaciers. Two prominent end moraines occur in the Park Region, the Wabash Moraine on which the park is located, and the Fort Wayne Moraine just to the east of the park. These two moraines are so close together in this area that they almost overlap, and are separated only by the St. Joseph River.
Ground Moraine (Till Plains)Continental glaciers also produce areas of relatively flat or gently rolling topography, called till plains in the Midwest, that are underlain by ground moraine. This type of moraine forms by deposition of sediment beneath glacial ice or by release of sediment during rapid down-melting. The resulting ground moraine surfaces (or till plains) commonly lie adjacent to and on the up-ice side of end moraines.
South of Fort Wayne, the Wabash and Fort Wayne Moraines diverge. The intervening relatively flat area is a till plain underlain by ground moraine. West and southwest of Huntertown, the relatively flat area just west of the Wabash Moraine is another good example of a till plain. Such till plains give large areas of northern Indiana their “featureless” appearance.
Ice-Marginal StreamsMeltwater streams are capable of carving valleys through older glacial deposits or even through bedrock. Some such streams follow the margins of glaciers, their main water source, whereas others follow paths leading away from the glaciers or even across end moraines. Meltwater streams commonly form along the margins of rapidly melting glaciers, thus taking on the shapes of the ice margins and marking the down-ice boundaries of the associated end moraines.
Several ice-marginal streams formed in the Metea Park Region along the west and southwest margins of the Wisconsinan ice lobes: a former upstream part of the Eel River northwest of the park (now called upper Cedar Creek), Aboit Creek southwest of the park, the St. Joseph River east and south of the park, and the St. Marys River south of Fort Wayne. Aboit Creek and the north-south trending upper section of Cedar Creek approximately mark the western boundary of the Wabash Moraine, and the St. Joseph and St. Marys Rivers mark the western and southwestern boundaries of the Fort Wayne Moraine.
The Wabash-Erie SluicewayWhere meltwater is funneled through a valley, the resulting landform is called a
sluiceway. Sluiceways (named after miners’ gold sluices) typically are underlain by outwash sand and gravel deposits, called valley trains, commonly capped with overlying silt and clay from later flooding. If the meltwater streams are not restricted to a valley, they may meander widely, distributing outwash over wide areas, resulting in broad flat surfaces called outwash plains.
Two prominent sluiceways formed in the Metea Park Region, perhaps the most striking of which is the valley that connects Fort Wayne and Huntington, known as the Wabash-Erie Sluiceway. This large, seemingly empty valley, today occupied only by the “underfit” Little River, was initially eroded by the headwater streams of the Wabash River (the St. Joseph and St. Marys Rivers), and later by sometimes torrential overflow from Glacial Lake Maumee.
The Eel River SluicewayThe Eel River also developed a major sluiceway that contains a very large deposit of sand and gravel outwash. The Eel River Sluiceway trends diagonally west-southwest across areas of ground moraine west of the Wabash Moraine, then crosses both the Salamonie and the Mississinewa Moraines before entering the modern Wabash River at Logansport. In some places this sluiceway is so broad that it has the appearance of an outwash plain.
The importance of the Eel River history for interpreting the history of the Metea Park Region is that the upper part of the Eel River system was captured by the stream that later became the present-day Cedar Creek
Stream Capture EventsThe St. Joseph and St. Marys RiversSteam capture events, sometimes called stream piracy, were relatively common in the Metea Park Region. Perhaps the most significant capture event occurred in what is now downtown Fort Wayne. There the Maumee River, which had formed on the drained surface of Glacial Lake Maumee, captured both the St. Joseph and St. Marys Rivers, causing their waters to be diverted from the Wabash-Erie Sluiceway into the Maumee and thus northeastward to Lake Erie.
Cedar CreekA few somewhat unusual meltwater streams trend across the end moraines produced by glaciers, instead of paralleling their margins. Cedar Creek was eroded by such a stream, but there is more to its history. A short westward-flowing glacial stream probably first carved the western end of the Cedar Creek valley. This low area then probably was used by a sub-ice stream, also flowing westward away from the glacier. It is thought that this “ice-tunnel stream” carved the unusually deep and steep-sided western valley of Cedar Creek (Bleuer and Moore, 1978).
However, it was not until the ice had melted away that Cedar Creek took on its modern appearance. A small tributary of the St. Joseph River eroded toward the westward-flowing Cedar Canyon stream by downcutting, possibly aided by overflow from the upper Eel River. Water flowing in the eastern part of the Cedar Creek valley thus flowed eastward, as now, into the St. Joseph River (Bleuer and Moore, 1978).
The Upper Eel RiverIf that weren’t enough, even the Eel River could not escape the capture process. Its south-flowing headwaters were captured by the now east-flowing waters of eastern Cedar Creek, “beheading” the Eel and adding more than 15 miles of stream course to Cedar Creek.
The Cedar Creek and Upper Eel River capture events probably were closely related in time, and together they resulted in a curious right-angle drainage pattern for Cedar Creek. This unusual stream now flows due south from the northwestern corner of Dekalb County, following the path of the former headwaters of the Eel River; it then takes a right-angle turn to the east across the Wabash Moraine, where it first flows through a deep (former sub-glacial?) canyon and emerges into a broader valley, then, at the east margin of the Wabash Moraine, Cedar Creek makes another right-angle turn to the south where it joins the St. Joseph River.
Cedar Creek is well worth all its accolades, and even today its complex history probably has not been completely unraveled.
ReferencesBleuer, N.K., and Moore, Michael C., 1978, Environmental Geology of Allen County, Indiana: Indiana Department of Natural Resources, Indiana Geological Survey Environmental Study 13, Bloomington, Indiana. 72 p.
Fleming, T., 1994, Groundwater Geology of Allen County, Indiana: Indiana Geological Survey Special Report, Indiana Geological Survey, Bloomington, Indiana.
Sunderman, J.A., 1987, Paleozoic and Pleistocene geology of the Fort Wayne, Indiana, area: Geological Society of America Centennial Field Guide Series, North-Central Volume, p. 325-332.
