Radiocarbon dating techniques, first developed by the American chemist WillardF. Libby and his associates at the University of Chicago in 1947, are very useful in deciphering time-related problems in archaeology, anthropology, oceanography, pedology, climatology, and recent geology. What is pedology???
The amount of carbon-14 in a living organismremains in balance with the amount of C-14 in the atmosphere or some other portion of the earths dynamic reservoirs, such as the ocean. Upon the organisms death, C-14 decays at a known rate, and no further replacement of C-14 can take place.The half-life of C-14 (~5730 years) limits the datingperiod to approximately 50,000 years, although the method is sometimes extended to 70,000 years.
Radioactive elements can be thought of as "clocks within the earths rocks” becausetheir consistent rates of radioactive decay allow estimation of the time that has passed since the rock solidified. I am a mass spectrophotometer! Mass spectrophotometers areused to quantify the abundance of specific isotopes in a material
Magnetostratigraphy is another technique used to date sedimentary and volcanic strata. The method works by collecting oriented samples at measured intervals throughout the section. The samples are analyzed to determine their detrital remnant magnetism (DRM), that is, the polarity of Earths magnetic field at the time a stratum was deposited. For sedimentary rocks, this is possible because when very fine- grained magnetic minerals fall through the water column, they orient themselves with Earths magnetic field. Upon burial, thatorientation is preserved. The minerals behave like tiny compasses. For volcanic rocks, magnetic minerals that form as the melt cools orient with the ambient magnetic field.
PRECAMBRIAN (4,500 to 543 mya) We don’t know much about what happened during the Precambrian periodin Illinois. Cascade style volcanics and granite intrusions occurred 1.5 billion years ago. Later, at 1.15 billion year ago the rifting (separating) of continental plates created a weak zone along which the Mississippi River later formed. This is the zone of the New Madrid Earthquake. CAMBRIAN (543 to 490 mya) Illinois was emergent for most of the Cambrian period. Toward the end of the Cambrian the sea came in and deposited the sands and muds that turned into the oldest dolomites, sandstones and shales now found in Illinois.
ORDOVICIAN (490 to 443 mya) Illinois was covered by shallow seas during the Ordovician period. Marine limestones and dolomites were deposited. In the late Ordovician, sands weredeposited. The St. Peter Sandstone, which formed from these sands, creates the backbone for Starved Rock, Buffalo Rock, and Mattheissen State Parks.
There are 18canyons at Starved Rock State Park. Most have waterfalls.
SILURIAN (443 - 417 mya) A shallow, tropical sea covered Illinois (then south of the equator) during the Silurian. Corals, crinoids, and shelled invertebrates flourished in the sea. In the late Silurian, thefirst-known land plants (Cooksonia) and air-breathing animals (millipedes and scorpions) appeared.
DEVONIAN (417 to 354 mya) Deep stagnant basins covered Illinois during the Devonianperiod. The sediments deposited in these basins turned into thick black shale deposits, which are also found in Indianaand Kentucky. Important biological changes occurred duringthis period such as the development of fish and amphibians. Shale gas reserves
MISSISSIPPIAN (354 to 323 mya) Shallow seas covered Illinois during the Mississippian period. More limestone was deposited forming the bluffs, caves andkarst topography of Western Illinois. The lead and zinc deposits of NW Illinois, Iowa, and Wisconsin were formed at this time.
PENNSYLVANIAN (323 to 290 mya) Tropical swamps dominated Illinois during thePennsylvanian period. These swamps formed the vast coal deposits that now underlie 2/3rd of the state. Land plants,spiders and insects were abundant as well strange swamp creatures like the Tully Monster (state fossil).
IL has enormous coal reserves that formed around 300 mya Coal underlies 37,000 square miles of Illinois -- about 65 percent of the states surface. Illinois coal reserves contain more Btus than the oil reserves of Saudi Arabia and Kuwait. Arguably the largest reserves of all US states ~ half of the coal in the eastern US ~ 1/5 of the coal in the US
The Mazon Creek site is located 60 miles west of Chicago.Spectacular fossils of Carboniferous forest plants such as horsetail, fern, seed fern, lycophyte trees, and cordaites (a group of now-extinct seed-bearing plants) are found here. The fossils formed in thefine iron rich sediments that are the defining feature of Mazon Creek.More than 300 animal species and 400 plants have been identified!
In most fossil deposits only the hard parts of organisms (shells, bones, teeth, etc.) are preserved. This means that in most fossil deposits only animals that have hard parts are preserved. Because of the unique conditions of fossilization, Mazon Creek fossils frequently have both hard and softer parts preserved. In addition, many soft-bodied organisms that do not usually fossilize were preserved. These factors mean that the fossils from Mazon Creek provide scientists with an extraordinary view of biodiversity 300 million years ago.Francis Tully ~ 1958
The Mazon Creek fossils are very unusual. When creatures died, they were rapidly buried insilty outwash. Bacteria that began to decompose the plant and animal remains produced carbon dioxide that reacted with iron in the groundwater forming a very durable crust of siderite (ironstone‘) – theseiron rich crusts remain today as casts of thousands of plants and animals. Mazon Creek fossils are one of the mostconcentrated and diverse assemblages of fossils in the world.
Why aren’t there any dinosaur bones in IL?IL bedrock geology
From ~1.8 million to ~12,000 years ago, massive sheets of ice advanced across northern North America many times. This period is known as the Pleistocene. Glaciers originating innorthwestern and northeastern Canada extended into parts of Illinois during long cold periods. They melted back during shorter warm phases of interglacial climate.
Over the last 750,000 years, ice sheets expanded into themidwestern United States at least 4 times. The timing of the earlier of these advances is not well known. The last glaciation of the midwestern United States had its maximum extent approximately 20,000 years ago.
Depth of loess cap LOESSsilt sized glacial flour,transported by wind,deposited near rivers Major reason we have fertile soils in the Midwest
In northern Chinas Loess Plateau the edges of terraced fieldsroutinely collapse down steep gullies. Farming on this fragileloess contributes to one of the worlds highest erosion rates.
The hilly terrain of the Palouse region of the US is underlain by a massive accumulation of loess—wind-blown, silt sized particles. The soils are very productive but highly prone to water erosion and annual soil loss >> 10 tons/ac is common. ?
Tundra vegetation established across IL as the glaciers retreated. http://www.sciencefriday.com/news/030907/tree.jpg
Next, for several thousand years while glacial ice persisted in southern Canada, Illinois was covered by boreal forest dominated by spruce, fir and black ash. As the climate warmed, the iceretreated and plants adapted to the boreal climate diminished. The annual average temperature continued to rise, and by ~11,000years ago, thick deciduous forest dominated by oak, elm, ash and hickory covered Illinois.
How is it possible to determine vegetative shifts that occurred thousands of years ago? Lake sediment contains abundant fossil pollen – commonly tens to hundreds of thousands of pollen grains per cubic centimeter of sediment. Because pollen is released into the air and transported long distances, the assemblage of pollen in sediment is representative of the vegetation from the general region, not a single, small area. Palynologists (i.e., scientists who study fossil pollen) can interpret a region’s long-term vegetative history from the layering of fossil pollen in sediment. Some lakes even have annual layers of sediment, like tree rings, that make it possible to interpret short-term vegetative/climate change.
Harlans muskox first appeared in North America in the early Pleistocene, around 500,000 years ago and lived all across North America south of the late Pleistocene ice sheets. Its fossils have been discovered at many sites in Illinois.
The Woolly Mammoth is one of three species of mammoth that inhabited North America. It was common in Illinois 10-40,000 years ago. Discovery sites are known throughout the state. It is thought that mammoths crossed the Bering Straits less than 500,000 years ago. They were contemporaneous with humansfor thousands of years. Mammoths were large and heavily furred. They stood up to 12 feet at the shoulder and had a large rounded dome and a sloping back.
Mastodon bones are also common in Illinois. Three discovery sites are in the Champaign-Urbana area—one is in east Urbana. Mastadons were common in the Midwest 10,000 - 40,000 years ago. Large and hairy, mastodons commonly stood 10 feet tall at the shoulder.
The vegetative shifts atthe end of Pleistoceneare likely to have been very challenging for Illinois’ megafauna.
The arrival of humans at the end of the Pleistocene also created challenges for the megafauna.
In 1979, paleontologists made an exciting Mastodon State Historic Sitediscovery at Kimmswick Bone Bed in Imperial, Missouri—stone spear points with mastodonbones. Clearly humans had visited Kimmswick to hunt the herds of animals that came to water at the spring-fed marsh located there.
About 8300 years ago, the climate in IL became substantially warmer and drier, and within 500 to 800 years, most of the oak hickoryforests died out, except along stream banks. During this time, prairie vegetation spread over much of IL.
An eastward extension of tallgrass prairie commonly called the Prairie Peninsula has been studied for many years. One of the questions that has long intrigued researchers is why this region was dominated by grassland vegetation during the Holocene. Evidence suggests that annual precipitation was normally more than enough to support trees. One of the key factors isthought to have been fire.Annual dry periods in the fall and early spring, periodic extended droughts, and the flatness of the land all promoted fire. In addition, the indigenous people arethought to have regularly set fires.
The hoof and grazing action of bison also helped to maintain the prairie Historical records suggest that the eastern Bison herds that frequented IL were much smaller than the vast western herds.
How many bison skulls doyou think are in this pile?
Tallgrass prairie once covered ~170 million acresof North America.> 850 prairie plant species just in IL
Famous illustration of tall grass prairie species – above and below ground 16ft
Submit answers using WO before the start of class next Wednesday (1/23) Reading questions for Prairie article http://web.extension.illinois.edu/illinoissteward/openarticle.cfm?ArticleID=517 1) Describe (in your own words) some of the key geologic and climatic changes that created the prairie dominated landscapes encountered by early IL settlers. 2) Which of the 4 main types of prairie ecosystems (INHS ecologists have actually identified over 20 types of prairies in IL) would you most like to visit? Describe some of the key characteristics of this type of prairie and explain why you would like to visit it. 3) Describe some of the main factors that led to rapid conversion of most of IL’s prairies to agriculture during the mid 1800s. Which types of prairies were the last to be converted to agriculture? Why? 4) Identify a prairie preserve that can be visited within 50 miles of your hometown. Use the web to track down some information about this preserve - describe a few interesting things you would be see if you were to go visit it.
Quantitative problem 5a) Estimate the total # of acres of prairie in IL when it became a state. (HINT ~ 55% of Illinois was prairie in 1818) 5b) If the amount of prairie in 1900 was 90% less than when IL became a state, calculate the average # of acres of prairie lost per year (i.e., between 1818 and 1900). Use any resources you like but explain all assumptions.Area of IL in square miles* 640 acres/square mile => ___ acres of prairie in 1818 90% of ___ acres of prairie in 1818 = ___ acres of prairie converted ___ acres of prairie converted / 82 years = ___ acres per year
Submit answers using WO before the start of class next Wednesday (1/23) Reading questions for Grove article http://web.extension.illinois.edu/illinoissteward/openarticle.cfm?ArticleID=489 1) Describe several reasons why early settlers tended to live in or near groves of trees. 2) Why were the groves mostly isolated islands in a sea of prairie and where did they tend to be located? 3) Describe what has happened to most of the groves in IL and why the surviving groves look very different than they did 200 years ago. 4) Describe why it is challenging to restore groves and explain your opinion regarding whether it is worth the effort to restore a grove.
Until recently, one of the most useful sources of historical information about pre-settlement Illinois ecosystems was largely overlooked. 1778 Survey records of the U.S. General Land Office (GLO) can be used toreconstruct presettlement landscapes and vegetation patterns in IL and many other upland regions of the United States.
General Land Office records are particularly useful to ecologists because they contain detailed descriptions of pre-settlement treecomposition and timberland structure, as well as maps showing the location and extent of former prairies, swamps, ponds, rivers, streams, marshlands, and timberlands. 1818Unlike historical narratives, GLO records provide us with quantitative data that can be used to reconstruct baseline conditions.
The present-day Illinois River occupies only a small partof an ancient river valley formed when the Illinois River valley was the drainage outlet for much of the UpperMississippi River basin. The ancient river that occupiedthe valley carried a much greater flow than the present Illinois River.
Ice sheets during the Illinoian glacial advance (~300,000 to 132,000 years before present) blocked the ancientMississippi near Rock Island, Illinois, diverting it to its present channel farther to the west, the current western border of Illinois. The Hennepin Canal roughly follows the ancient channel of the Mississippi downstream from Rock Island to Hennepin, Illinois. South of Hennepin, to Alton, Illinois, thecurrent Illinois River follows the ancient channel used by the Mississippi River.
Over geologic time, riverschange courses many times
During floods, old channelsoften become filled with water.
With greatly reduced flow and a smaller channel that occupied only asmall portion of the valley, the water flowing down the modern Illinoisriver could not transport the sediment delivered by tributary streams, resulting in the formation of alluvial fans and deltas near the mouths of the tributary streams.
These fans and deltas created narrow constrictions that heldback water in the deeper channels and depressions in the floodplain forming some of the bigger bottomland lakes in the valley. Natural levees were also created along the riverbanks by deposition of sediment from overbank flows during floods,isolating old channels, sloughs, depressions, and lakes from themain river. Over time these natural processes have created many bottomland lakes along the Illinois River valley.
In 1908, the Illinois River fishery produced a higher percentage of the U.S. harvest offreshwater fish than any other North American river. The river supported more than 2,000commercial fishermen and produced an annual commercial catch of 24 million pounds.
The Upper Mississippi Basin historically provided quality habitat for an estimated 10 to 40 million beaver. These industrious animals built dams 400 to 500 feet apart on small streams; dams that, during storms, delayed the movement of rainwater to the main channels. Following Euro- American settlement, demand for beaver pelts and reduction of theirhabitat drastically reduced North American beaver populations. While the beaver couldprovide flood control in Illinois, not everyone would welcome back the beaver, as they damaged trees, build dams and flood areas irrespective of human property rights.
Vast numbers of birds have used the Mississippi flyway for breeding and/or wintering grounds for thousands of years.Mallard ducks, which nest on islands or in grasslands adjacent to the river are the dominant flyway waterfowl species. Eastern prairie populations of Canada geese, snow geese, white-fronted geese, gadwall, blue winged teal, green-winged teal, American widgeon, American black duck, and northern pintail are also major species.A number of land and predatory birds, such as the peregrine falcon, Swainson’s hawk, eastern kingbird, summer tanager, and yellow billed cuckoo also use the flyway.
Total number of species: 53,754+Total number of extirpated species: 114Total number of threatened/endangered species: 503