Two Creeks Buried Forest State Natural Area is a site in the Wisconsin State Natural Areas Program and a unit of the Ice Age National Scientific Reserve. The site lies in the northeast corner of Manitowoc County on the shore of

Lake Michigan Lake Michigan ( ) is one of the five Great Lakes of North America. It is the second-largest of the Great Lakes by volume () and depth () after Lake Superior and the third-largest by surface area (), after Lake Superior and Lake Huron. To the ...

north of Two Creeks, Wisconsin, USA. Periodically exposed in a steep lakeshore bluff is a

stratum In geology and related fields, a stratum (: strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ...

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

, known as the Two Creeks forest bed. It contains stumps, logs, branches, pine needles, pinecones, moss, and other forest litter and is sandwiched between layers of

glacial till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...

. This is an important site in Great Lakes

geochronology Geochronology is the science of Chronological dating, determining the age of rock (geology), rocks, fossils, and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes, ...

because it firmly establishes the timeframe of advances and retreats during the last glacial period in this region.Black, R.F., 1974
''Geology of the Ice Age National Scientific Reserve of Wisconsin''.
''U.S. National Park Service Scientific Monograph Series,'' 2, 234 pp. As summarized in Rech and others, various studies have dated the buried logs and stumps from the Two Creeks forest using

radiocarbon dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for Chronological dating, determining the age of an object containing organic material by using the properties of carbon-14, radiocarbon, a radioactive Isotop ...

and analyzed their growth rings to determine a minimum lifespan for the forest.Rech, J.A., Nekola, J.C. and Pigati, J.S., 2012. ''Radiocarbon ages of terrestrial gastropods extend duration of ice-free conditions at the Two Creeks forest bed, Wisconsin, USA.'' ''Quaternary Research'', 77(2), pp.289-292. Initial research into the age of this buried forest indicated an

calibrated In measurement technology and metrology, calibration is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known ...

age range of ~13,840–13,620 cal BP and a minimum lifespan for the forest of ~230 to 250 yr.Broecker, W.S. and Farrand, W.R., 1963. ''Radiocarbon age of the Two Creeks forest bed, Wisconsin.'' ''Geological Society of America Bulletin'', 74(6), pp.795-802.Kaiser, K.F., 1994. ''Two Creeks Interstade dated through dendrochronology and AMS.'' Quaternary Research, 42(3), pp.288-298. Later research by Leavitt and others indicated a minimum lifespan of 329 yr for the Two Creeks and an age range of 13,760–13,530 cal BP. Leavitt, S.W., Panyushkina, I.P., Lange, T., Cheng, L., Schneider, A.F. and Hughes, J., 2007. ''Radiocarbon “wiggles” in great lakes wood at about 10,000 to 12,000 BP.'' ''Radiocarbon'', 49(2), pp.855-864. The lower layer of glacial till was deposited during the end of the Woodfordian substage of the

Wisconsin glaciation The Wisconsin glaciation, also called the Wisconsin glacial episode, was the most recent glacial period of the North American ice sheet complex, peaking more than 20,000 years ago. This advance included the Cordilleran Ice Sheet, which nucleated ...

. The remains in the park demonstrate that a warmer interval, called the ''Twocreekan substage'', followed in which the

glacier A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

retreated and a forest of

spruce A spruce is a tree of the genus ''Picea'' ( ), a genus of about 40 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal ecosystem, boreal (taiga) regions of the Northern hemisphere. ''Picea'' ...

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

, and hemlock grew. Then the climate cooled again and the Greatlakean substage began.Evenson, E.B., Farrand, W.R., Eschman, D.F., Mickelson, D.M. and Maher, L.J., 1976. ''Greatlakean substage: a replacement for valderan substage in the lake Michigan basin.'' ''Quaternary Research'', 6(3), pp.411-424. A glacial tongue blocked Lake Michigan's drainage, causing the water level to rise and flood the forest, carrying in sediments which buried the forest floor. The glacier proceeded to flow over the forest, flattening it and ultimately depositing another layer of glacial till over it.Mickelson, D.M., Hooyer, T.S., Socha, B.J., Winguth, C., 2007. ''Late-glacial ice advances and vegetation changes in east-central Wisconsin.'' In: Hooyer, T.S. (Ed.), ''Late-Glacial History of East-Central Wisconsin'', ''Wisconsin Geological and Natural History Survey Open-File Report'', 2007-01. pp. 72–87. Two Creeks Buried Forest State Natural Area is open to visitation. There is an historical marker at the location. The site has no trails or displays, but visitors can park in the northwest corner of the site and wander freely across the grounds. Collection of any material is prohibited.Meyer, T., ed. ''Wisconsin, Naturally: A Guide to 150 Great State Natural Areas''. Madison, Wisconsin, Wisconsin Department of Natural Resources, Bureau of Endangered Resources, State Natural Areas Program, 184 pp.

References

External links

Two Creeks Buried Forest State Natural Area
from the National Park Service {{authority control Ice Age National Scientific Reserve Cenozoic paleontological sites of North America Protected areas established in 1967 Protected areas of Manitowoc County, Wisconsin State Natural Areas of Wisconsin Paleontology in Wisconsin Fossil parks in the United States 1967 establishments in Wisconsin