WISCONSIN GLACIAL LANDFORMS

A. Introduction

Time divisions

divisions of geologic time based on intervals of interpreted contrasting climates; boundaries are not synchronous

glacial/interglacial

stage & substage: e.g. Wisconsin Stage; early , middle & late substages

stadial/interstadial within substages

phases: geologic events, not time periods

Late Ice Age divisions

Illinoian Glaciation: 302,000- 132,000 YBP

Early Illinoian and Late Illinoian

Sangamon Interglacial: 132,000 - 115,000 YBP or 75,000 YBP

Wisconsin Glaciation 115,000 or 75,000 - 10,000 YBP

Early Wisconsin

Middle Wisconsin

Late Wisconsin: 25,000-10,000 YBP

Lithostratigraphic units of Wisconsin (WGNHS handout)

unit defined by their properties (e.g. color, texture, particle shape, stratification, lithology)

formation: a main unit that has considerable lateral extent

member: a named unit within a formation; names are geographical

stratigraphic sequencing

younger units overlie older units

younger units truncate older units

younger units are behind older units

B. Pre-Illinoian Deposits & Landforms

Pierce Formation

Kinnickinnic Member: lacustrine silt & clay

Hersey Member: till; silt-rich, kaolinite rich

peat & wood

Woodville Member: till; grey-brown, silt-rich, kaolinite rich

Eau Galle Member: lake sediment

Marathon Formation

Edgar Members: till; Marshfield moraine

Medford Member: till

calcareous, gray to brown, silty, limestone clasts, gray shale fragments

source: neither Lake Superior nor Lake Michigan basins

C. Illinoian Deposits & Landforms

Western Wisconsin

River Falls Formation: till; overlies Pierce formation; deeply weathered during Sangamon

Bakerville Member of Lincoln Formation; till

reddish-brown sandy till, abundant basalt & red sandstone clasts from Lake Superior basin

extensively eroded

Southern Wisconsin

Walworth Formation; till from Lake Michigan lowland

D. Wisconsinan Glaciation Pre 25 ka YBP

Pre-late Wisconsinan

Merrill Member of Lincoln Formation (central Wisconsin); units Ltr, gm & gmh

little stream incision; mildly weathered

reddish-brown sandy till

till plain: gently rolling topography (unit gm) or slightly hilly (unit gmh)

underlying bedrock affects topography

Capron Member of the Zenda Formation (southern Wisconsin)

E. Late Wisconsinan 25,000-10,000 YBP

Introduction

ice crossed southern Lake Superior drainage divide ~26,000 YBP

Green Bay and Langlade Lobes advanced over northeastern Wisconsin by ~20,000 YBP

ice reached maximum extent by~ 20,000-18,000 YBP

ice stayed at maximum until ~15,000 YBP

ice sheet melted from northeastern Wisconsin before ~12,000 YBP

Woodfordian substage

Superior Lobe - Copper Falls Formation

Poskin Member: till; indistinct landforms

Sylvan Lake Member: St. Croix moraine; hummocks, ice-walled lake plains, tunnel channels; dominated by sand

Superior Lobe - Miller Creek Formation

silt & clay rich till derived from lake sediments

After Clayton et al. (2006) WGNHS Ed. Series 36

Chippewa Lobe - Copper Falls Formation

End moraines: Late Chippewa, Perkinstown

hummocky, up to 20 km wide, ice-walled lake plains, supraglacial sediment

Wisconsin Valley Lobe - Copper Falls Formation

End moraines: Harrison

hilly, up to 10 km wide, ice-walled lake plains

Langlade Lobe - Copper Falls Formation

Nashville Member: reddish brown, uniform sandy basal till, less uniform supraglacial till, non-dolomitic

higher percentage igneous & metamorphic, and less sedimentary rock than Green Bay Lobe

End moraines:

Parrish: single-crested ridge, hummocky end moraine complex with some ice-walled lake plains

Summit Lake: high relief in places, no ice-walled lake plains or hummocky topography

numerous drumlins in northern parts oriented NE to SW

composed of sand & gravel with thin till veneer, wet based ice ~1000 m thick

composed of till & debris flow sediment

some may have core of stratified sand & gravelly sand

Lincoln, Marathon, and Holy Hill (Mapleview Member) Formations found beneath Nashvill Member in places

Langlade Lobe & Green Bay Lobe intermixed along border; cross-striations

Crab Lake Member: reddish brown, gravelly sandy loam, majority of rocks igneous & metamorphic

Ontonagan Lobe flowed into region after Langlade & Wisconsin Valley Lobes had wasted away

Green Bay Lobe - Holy Hill Formation

Wisconsin Valley, Chippewa & Superior Lobes melted back prior to Green Bay and Langlade Lobes

Ice flowed northwestward at the northwestern margin of the lobe

Mapleview Member:

Hancock end moraine; at northern end ice advance up a regional slope & when ice retreated, meltwater sediments flowed parallel to ice margin; much of till covered by outwash; Almond recessional moraine; 10-20 m high & 0.5 to 1.0 km wide

yellowish-brown or brown, sandy till, calcareous, granitic clasts from Wolf River Batholith

single ridge end moraines; average 1-1.5 km wide; steep front; hummocky topography, boulders common, tunnel channels, some ice-walled lake plains

ice frozen to bed along margin but not farther back; no drumlins behind terminal moraine

recessional moraines missing hummocky topography; narrow ridges with drumlins located behind

Keene Member:

Arnott end moraine

non- to slightly calcareous, brown to reddish brown sandy till, granitic clasts from Wolf River Batholith

more weathered and more eroded than Mapleview Member

most likely Illinoian or older in age

Horicon Member:

brown, sandy till; slightly finer textured than Mapleview Member, and contains less quartz and more dolomite than Mapleview Member

Johnstown end moraine: simple ridge in places, hummocky in other places; smaller than Hancock & Almond moraines to the north; 5-10 m high & 20-100 m wide

drumlin field

large drumlins: 0.2-0.4 km wide, 0.5-2.0 km long, 10-30 m high, incompletely streamlined by subglacial remolding, non-uniform orientation, may have core of dolomite, sandstone or erosional remnants of preglacial landforms; incompletely molded at base of glacier

small drumlins: several m high, ~10 m wide, up to 2.0 km long, more streamlined, uniform orientation; fully molded at base of glacier

Green Bay Lobe - Kewaunee Formation

Ice retreated to north end of Lake Michigan basin; water & reddish-brown sediment flowed from Lake Superior basin into Lake Michigan basin

Silver Cliff Member

up to 1 meter loess cover in areas; siltier than Nashville or Mapleview Members

ice wastage & formation of proglacial lakes, followed by readvance that transported silt-rich lake sediment

Kirby Lake Member

gently rolling low relief topography

reddish brown, dolomitic, silty clay

thick loess & dunes in areas

Middle Inlet Member

overlies Kirby Lake Member

reddish brown, less clay than Kirby Lake

relatively flat topography

Intersection of Green Bay and Lake Michigan Lobes - Kewaunee Formation

Age relationships (from youngest to oldest)

Green Bay: Middle Inlet & Glenmore = Lake Michigan: Two Rivers

Green Bay: Kirby Lake & Chilton = Lake Michigan: Valders

Green Bay: Silver Cliff = Lake Michigan: Ozaukee

Two Creeks buried forest sequence:

Lacustrine sediments

Two Rivers Member Kewaunee Fm

Lacustrine sediments

Two Creeks buried forest & paleosol in lacustrine sediments

Valders Member Kewaunee Fm

IF more glacial sediments were buried beneath this, they would be:

Haven Member Kewaunee Fm

Ozaukee Member Kewaunee Fm

Oak Creek Fm

Image credit: NOAA National Geophysical Data Center. http://www.ngdc.noaa.gov/mgg/greatlakes/lakemich_cdrom/html/geomorph.htm

After Clayton et al. (2006) WGNHS Ed. Series 36

Green Bay Lobe - Oak Creek Formation

grey silty-clay till

F. Summary

Des Moines, Superior, Chippewa, Wisconsin Valley, & Langlade Lobes

Miller Creek Formation

red silt & clay-rich till, calcareous, from Lake Superior basin

topography modified by lake or wave action

Trade River Formation

Copper Falls Formation

reddish-brown, sandy till, slightly calcareous, igneous & metamorphic clasts from Lake Superior basin

broad hummocky end moraines with ice-walled lake plains & tunnel channels

Lincoln Formation

brown to reddish-brown, sandy till, rock fragments from Lake Superior basin

no primary glacial topography; extensively eroded

River Falls Formation

reddish-brown, sandy till, basalt & red sandstone clasts from Lake Superior basin

Marathon Formation

yellowish or greyish-brown, silt-rich till, calcareous

no primary glacial topography; deep stream incision

Pierce Formation

grey-brown, silt-rich till & lacustrine sediments

no primary glacial topography

Green Bay & Lake Michigan Lobes

Kewaunee Formation

reddish clay till

subdued topography

Oak Creek Formation

Holy Hill Formation

brown, sandy till, calcareous, clasts from Wolf River Batholith

single-crest moraines, tunnel channels; drumlins behind end moraines only where bed wasn't frozen

After Clayton et al. (2006) WGNHS Ed. Series 36