The Mazon Creek fossil beds are a conservation found near Morris

Morris, Illinois

Morris is a city in Grundy County, Illinois, United States. The population was 13,636 at the 2010 census.Morris is home to the Dresden Nuclear Power Plant, which provides a substantial portion of the electricity supply for the Chicago metropolitan area...

, in Grundy County, Illinois. The fossil

Fossil

Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...

 beds are located in ironstone

Ironstone

Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical repacement, that contains a substantial proportion of an iron compound from which iron either can be or once was smelted commercially. This term is customarily restricted to hard coarsely...

 concretion

Concretion

A concretion is a volume of sedimentary rock in which a mineral cement fills the porosity . Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word 'concretion' is derived from the Latin con meaning 'together' and crescere meaning 'to grow'...

s, formed approximately in the mid-Pennsylvanian

Pennsylvanian

The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...

 epoch of the Carboniferous

Carboniferous

The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

 period. These concretions frequently preserve both hard and soft tissues

Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 of animal and plant materials, as well as many soft-bodied organisms that do not normally fossilize. The quality, quantity and diversity of fossils in the area, known since the mid-nineteenth century, make the Mazon Creek important to paleontologists, in attempting to reconstruct the paleoecology

Paleoecology

Paleoecology uses data from fossils and subfossils to reconstruct the ecosystems of the past. It involves the study of fossil organisms and their associated remains, including their life cycle, living interactions, natural environment, and manner of death and burial to reconstruct the...

 of the sites. The locality was declared a National Historic Landmark

National Historic Landmark

A National Historic Landmark is a building, site, structure, object, or district, that is officially recognized by the United States government for its historical significance...

 in 1997.

Geology

The Mazon Creek fossils are found in the Upper Carboniferous Francis Creek Shale; the type locality

Type locality (geology)

Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....

 is the Mazon River

Mazon River

The Mazon River or "Mazon Creek", is a tributary of the Illinois River in the United States. The confluence is near Morris, Illinois.The Mazon River is associated with the Mazon Creek fossils of the Francis Creek Shale, which are also exposed in strip mines and quarries near the River...

 (or Mazon Creek), a tributary of the Illinois River

Illinois River

The Illinois River is a principal tributary of the Mississippi River, approximately long, in the State of Illinois. The river drains a large section of central Illinois, with a drainage basin of . This river was important among Native Americans and early French traders as the principal water route...

 near Morris

Morris, Illinois

Morris is a city in Grundy County, Illinois, United States. The population was 13,636 at the 2010 census.Morris is home to the Dresden Nuclear Power Plant, which provides a substantial portion of the electricity supply for the Chicago metropolitan area...

, Grundy County, Illinois. The 25 to 30 meters of shale

Shale

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering...

 were formed approximately , during the Pennsylvanian

Pennsylvanian

The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...

 period. The fossiliferous concretions are usually found within the thickest deposits of Francis Creek. The concretions occur in localized deposits within the silty to sandy mudstone

Mudstone

Mudstone is a fine grained sedimentary rock whose original constituents were clays or muds. Grain size is up to 0.0625 mm with individual grains too small to be distinguished without a microscope. With increased pressure over time the platey clay minerals may become aligned, with the...

s, in the lower four metres of the formation. The paleoecosystem is believed to be a large river delta

River delta

A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...

 system, deposited by at least one major river system flowing from the northeast. The sediments are believed to derive from the Appalachian orogeny events. The delta had a tropical climate, a result of the area being within 10° north latitude

Latitude

In geography, the latitude of a location on the Earth is the angular distance of that location south or north of the Equator. The latitude is an angle, and is usually measured in degrees . The equator has a latitude of 0°, the North pole has a latitude of 90° north , and the South pole has a...

 of the equator

Equator

An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....

 during the Pennsylvanian

Pennsylvanian

The Pennsylvanian is, in the ICS geologic timescale, the younger of two subperiods of the Carboniferous Period. It lasted from roughly . As with most other geochronologic units, the rock beds that define the Pennsylvanian are well identified, but the exact date of the start and end are uncertain...

.

The remains of plants and animals were rapidly buried by the sediment

Sediment

Sediment is naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of fluids such as wind, water, or ice, and/or by the force of gravity acting on the particle itself....

 deposited in the deltaic system. Bacterial decomposition

Decomposition

Decomposition is the process by which organic material is broken down into simpler forms of matter. The process is essential for recycling the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death...

 of the remains produced carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 that combined with dissolved iron from the groundwater

Groundwater

Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

. This process formed siderite

Siderite

Siderite is a mineral composed of iron carbonate FeCO3. It takes its name from the Greek word σίδηρος sideros, “iron”. It is a valuable iron mineral, since it is 48% iron and contains no sulfur or phosphorus...

 in the sediments surrounding the remains, forming detailed casts of their structure. Lithification of the sediments formed protective nodules of ironstone around the now fossilized remains. This mode of preservation is known as authigenic mineralisation.

The fossiliferous concretions are found in the Mazon River area of Grundy, Will

Will County, Illinois

As of the census of 2000, there were 502,266 people, 167,542 households, and 131,017 families residing in the county. The population density was 600 people per square mile . There were 175,524 housing units at an average density of 210 per square mile...

, Kankakee

Kankakee County, Illinois

Kankakee County is a county located in the U.S. state of Illinois. According to the 2010 census, it has a population of 113,449, which is an increase of 9.3% from 103,833 in 2000. Its county seat is Kankakee....

, and Livingston

Livingston County, Illinois

Livingston County is a county located in the U.S. state of Illinois. According to the 2010 census, it has a population of 38,950, which is a decrease of 1.8% from 39,678 in 2000. Its county seat is Pontiac....

 counties. Additional fossils are found in LaSalle County, Illinois; between the Vermilion River

Vermilion River (Illinois River tributary)

The Vermilion River is a tributary of the Illinois River in the state of Illinois, United States. The river flows north, in contrast to a second Vermilion River in Illinois, which flows south to the Wabash River...

 and Marseilles, Illinois

Marseilles, Illinois

Marseilles is a city in LaSalle County, Illinois, United States. The population was 4,655 at the 2000 census. It is part of the Ottawa–Streator Micropolitan Statistical Area.-History:...

. The ironstone concretions are recovered from exposures along streams, roadcuts and in active or abandoned coal mine areas.

The site's importance was realized in the mid-nineteenth century: "the nodules of Mazon Creek, where fragments of plants, even of the softest texture, have been preserved in their integrity".

Flora

The Mazon Creek flora comprises over 400 species from at least 130 genera. However, the true number of species is difficult to determine. Paleobotanists name separate plant structures with different names by convention, inflating the number of fossil plant taxa. Paleobotanists are currently determining which taxa are valid.

Mazon Creek flora includes: lycopsids, related to modern club moss, with arborescent forms named Lepidophloios, Sigillaria

Sigillaria

Sigillaria is a genus of extinct, spore-bearing, arborescent plants which flourished in the Late Carboniferous period but dwindled to extinction in the early Permian period. It was a lycopodiophyte, and is related to the lycopsids, or club-mosses, but even more closely to quillworts, as was its...

and Lepidodendron

Lepidodendron

Lepidodendron is an extinct genus of primitive, vascular, arborescent plant related to the Lycopsids . It was part of the coal forest flora. They sometimes reached heights of over , and the trunks were often over in diameter, and thrived during the Carboniferous period...

, and herbaceous forms called Lycopodites and Cormophyton; sphenopsids like Calamites

Calamites

Calamites is a genus of extinct arborescent horsetails to which the modern horsetails are closely related. Unlike their herbaceous modern cousins, these plants were medium-sized trees, growing to heights of more than 30 meters...

a tree-like horsetail

Horsetail

Equisetum is the only living genus in the Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds.Equisetum is a "living fossil", as it is the only living genus of the entire class Equisetopsida, which for over one hundred million years was much more diverse and...

 relative, with common foliage names of Annularia

Annularia

Annularia is a plant fossil from the Carboniferous . It is a form taxon. Its radiating structures are most likely the leaves of Calamites....

and Asterophyllites, and a vine-like form called Sphenophyllum

Sphenophyllum

Sphenophyllum is a genus in the order Sphenophyllales....

; Pteridophyta as marattitalean tree ferns and Filicales and Zygopteridales understory ferns, with common foliage names of Pecopteris

Pecopteris

Pecopteris was a form genus of leaves from several unrelated plant groups that flourished the early Carboniferous period and on to c. 250 Ma. Pecopteris first appeared in the Devonian period, but flourished in the Carboniferous, especially the Pennsylvanian...

, Acitheca

Acitheca

Acitheca is a genus of fungi within the Gymnoascaceae family. This is a monotypic genus, containing the single species Acitheca purpurea.-External links:* at Index Fungorum...

and Lobatopteris; pteridosperms, also known as seed ferns, an extinct group of plants that grew both as trees and smaller shrubs, with features like pinnated leafs similar to true ferns, but reproduced by seeds instead of spores; they had common foliage names Mariopteris, Alethopteris

Alethopteris

Alethopteris is an genus of fossil seed ferns that existed in the Carboniferous period ....

, Odontopteris, Neuropteris

Neuropteris

Neuropteris is an extinct seed fern that existed in the Carboniferous period, known only from fossils.Major species include Neuropteris loschi....

, Laveineopteris and Macroneuropteris; extinct gymnosperm

Gymnosperm

The gymnosperms are a group of seed-bearing plants that includes conifers, cycads, Ginkgo, and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of their seeds...

 Cordaites

Cordaites

Cordaites is an important genus of extinct gymnosperms which grew on wet ground similar to the Everglades in Florida. Brackish water mussels and crustacea are found frequently between the roots of these trees. The fossils are found in rock sections from the Upper Carboniferous of the Dutch -...

, believed to be closely related to and sharing many features with modern conifers.

Fauna

The Mazon Creek fauna has over 320 species of animals that have been identified. The fauna is divided into two components: the marine

Ocean

An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...

 Essex fauna and the land and freshwater

Freshwater

Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...

 Braidwood fauna, that were washed into the deltaic sediments. The Essex fauna includes jellyfish

Jellyfish

Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...

, sea worm

Worm

The term worm refers to an obsolete taxon used by Carolus Linnaeus and Jean-Baptiste Lamarck for all non-arthropod invertebrate animals, and stems from the Old English word wyrm. Currently it is used to describe many different distantly-related animals that typically have a long cylindrical...

s, snail

Snail

Snail is a common name applied to most of the members of the molluscan class Gastropoda that have coiled shells in the adult stage. When the word is used in its most general sense, it includes sea snails, land snails and freshwater snails. The word snail without any qualifier is however more often...

s, saltwater clam

Clam

The word "clam" can be applied to freshwater mussels, and other freshwater bivalves, as well as marine bivalves.In the United States, "clam" can be used in several different ways: one, as a general term covering all bivalve molluscs...

s, shrimp

Shrimp

Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important...

, sea scorpion

Sea Scorpion

Sea Scorpion may refer to:* Eurypterids, members of the extinct class Eurypterida* some members of the Cottidae family of fish including the Long-spined Sea Scorpion and Short-spined Sea Scorpion...

s, cephalopods and fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

. The Braidwood fauna includes insect

Insect

Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...

s, millipede

Millipede

Millipedes are arthropods that have two pairs of legs per segment . Each segment that has two pairs of legs is a result of two single segments fused together as one...

s, centipede

Centipede

Centipedes are arthropods belonging to the class Chilopoda of the subphylum Myriapoda. They are elongated metameric animals with one pair of legs per body segment. Despite the name, centipedes can have a varying number of legs from under 20 to over 300. Centipedes have an odd number of pairs of...

s, scorpion

Scorpion

Scorpions are predatory arthropod animals of the order Scorpiones within the class Arachnida. They have eight legs and are easily recognized by the pair of grasping claws and the narrow, segmented tail, often carried in a characteristic forward curve over the back, ending with a venomous stinger...

s, spider

Spider

Spiders are air-breathing arthropods that have eight legs, and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other groups of organisms...

s, other arachnid

Arachnid

Arachnids are a class of joint-legged invertebrate animals in the subphylum Chelicerata. All arachnids have eight legs, although in some species the front pair may convert to a sensory function. The term is derived from the Greek words , meaning "spider".Almost all extant arachnids are terrestrial...

s, amphibian

Amphibian

Amphibians , are a class of vertebrate animals including animals such as toads, frogs, caecilians, and salamanders. They are characterized as non-amniote ectothermic tetrapods...

s, freshwater fish, freshwater shrimps, freshwater horseshoe crab

Horseshoe crab

The Atlantic horseshoe crab, Limulus polyphemus, is a marine chelicerate arthropod. Despite its name, it is more closely related to spiders, ticks, and scorpions than to crabs. Horseshoe crabs are most commonly found in the Gulf of Mexico and along the northern Atlantic coast of North America...

s and ostracod

Ostracod

Ostracoda is a class of the Crustacea, sometimes known as the seed shrimp because of their appearance. Some 65,000 species have been identified, grouped into several orders....

s. The oldest known beetle

Beetle

Coleoptera is an order of insects commonly called beetles. The word "coleoptera" is from the Greek , koleos, "sheath"; and , pteron, "wing", thus "sheathed wing". Coleoptera contains more species than any other order, constituting almost 25% of all known life-forms...

 has been described from the Braidwood fauna.

Three species of centipede have been described from Mazon Creek. They are known from around 60 specimens in total, and belong to three species:

• Latzelia primordialis Scudder
  Samuel Hubbard Scudder
  Samuel Hubbard Scudder was an American entomologist and palaeontologist.Born in Boston, Massachusetts, Scudder may be most widely known for his essay on the importance of first-hand, careful observation in the natural sciences...
  
  , 1890 (Scutigeromorpha)
• Mazoscolopendra richardsoni Mundel, 1979 (Scolopendromorpha)
• Palenarthrus impressus Scudder, 1890 (Scolopendromorpha)

Fossil centipedes are very rare, and Mazoscolopendra and Palenarthrus are the only known Paleozoic

Paleozoic

The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...

 scolopendromorphs.

The most famous faunal member is Illinois' state fossil Tullimonstrum, known popularly as the "Tully Monster".

External links

• Illinois State Museum Mazon Creek Fossil Exhibit
• UC Berkeley Mazon Creek info
• Northeastern Illinois University fossil fauna
• Fossil News generalized diagram of Mazon Creek Delta and fossil photos
• University of Bristol Mazon Creek flora and fauna discussed with photographed fossils
• Mazon River Watershed Website