Matanuska Formation
Encyclopedia
The Matanuska Formation consists of more than 3 km (1.9 mi) of sedimentary
strata
exposed in the northern Chugach Mountains
, Matanuska Valley, and southern Talkeetna Mountains
of South-Central Alaska
. The Matanuska Formation contains strata from Early Cretaceous (Albian) to Late Cretaceous (Maestrichtian). Parts of the formation contain abundant marine mollusks
, foraminifera
, and radiolaria
. Fossils of non-marine plants are found in some beds. Fossils of two dinosaurs have been recovered from marine mudstones in the formation. The lower Matanuska Formation (MF) is several hundred meters thick and includes non-marine and marine sediments. Campanian-Maastrichtian graded sandstone, conglomerate, and mudstone comprise the upper 2000 meters of the Formation.
Pasch and May reported that a hadrosaurid
was found in the Matanuska Formation. Its discovery heralded the knowledge of a new high-latitude source of dinosaur fossils. This was the first occurrence of a hadrosaur in south-central Alaska, one out of only four vertebrate fossils from the entire Wrangellia Composite Terrane, and the first associated skeleton of an individual dinosaur in Alaska. The carcass appeared to have been deposited in a bathyal or outer shelf environment. Scavenged bones are preserved in soft mudstone
while intact bones were presevered in calcareous
concretions. Some calcareous concretions may be the result of pieces of meat falling off as the carcass disintegrated. The hadrosaurid was a geographic link between the hadrosaurs of north america and asia.
The "Talkeetna Mountains Hadrosaur" specimen was discovered in 1994
in a quarry being excavated for road material. That fall, excavation began, and was resumed in the summer of 1996
. The specimen is housed at the University of Alaska Museum. The quarry is near the Glenn Highway
, approximately 150 miles northeast of Anchorage. The layer consists of dark grey marine mudstone that weathers easily. The mudstone contains highly indurated calcareous concretions and finely disseminated pyrite
crystals. Fresh wet surface display horizontal lamina, ripples and evidence of bioturbation
. Evidence that these strata have experienced deformation
after deposition include "joint sets, faults, secondary deposition of calcite, and degree of induration."
The strata's foraminiferans and mollusks all point to a middle Turonian
age for the formation
. Muramotoceras
is an unusual heteromorph previously known only from Japan. It is also middle Turonian. Eubostrychoceras
is known from Japan, Germany, and Madagascar. E. japonicum is Turonian, and likely confined to the middle Turonian. The authors reported teleost tooth and jaw fragments as well as wood fragments from the formation. Other Matanuska fossils include scaphopods, foraminifera, and palynomorphs. The quarry belongs to the lower region of C-1, an informal stratigraphic unit, and Member Four.
The "Talkeetna Mountains Hadrosaur" was an juvenile animal about 3 m (10 feet) long. The bones of the forelimbs with partial manus and ribs have been positively identified, as have most of the tail vertebrae Pelvis and dorsal vertebrae tentatively identified. The specimen could not be distinguished as a hadrosaurid or lambeosaurid. Aspects of its anatomy greatly differed from Edmontosaurus
.
The thin shelled heteromorphic ammonites probably lived at depths 36–183 m. Inoceramids tended to be at upper bathyal and neritic environments. The pyrite around the animal may have been the result of sulfur
produced by bacteria consuming the carcass. Invertebrate shells lie parallel to bedding. The high quality of the invertebrate fossils and their lack of any sign of biological action on the part of encrusting or boring
invertebrates suggest that there weren't many animals in the environment and only arrive at the location after dying. It is possible that mudslides could have transported the shells to the location, meaning that the preserved collection of species might not represent a specific ecosystem
. It may have also been possible for dead ammonites to float long distances. Heteromorphic ammonites probably didn't drift as far due to their potentially benthic mode of life or the septum
closing off the living chamber not being calcified and decomposing after death. The most abundant mollusks in the quarry are inoceramids. The ecological context indicates that the "Talkeetna Mountains Hadrosaur" was buried at a depth greater than 35 m.
The skull fell off before the carcass sank. The body came to rest on its left side with limbs extended to the east. About 20% of the hadrosaur's bones were envloped by calcareous concretions. There were 20 concretions recovered. Every element not found in a concretion bore many closely spaced ovualar conical depressions ranging in diameter from 2.12 to 5.81 mm and 1.64 to 3.62 deep. The depressions are probably bite marks. The depressions are not symmetrical enough for gastropod drill marks and are not shaped like sponge borings. None of the preserved fish fossils of the formation fit the size or geometry of the borings. The size and spacing and shape by contrast resembles closeley the teeth of the mosasaur
species Tylosaurus proriger. If the damage to the body had been done prior to being washed out to sea, it likely would have punctured the body, preventing the build up of bloating gases that allowed the carcass to drift out to sea in the first place. The distribution of bite marks corresponds inversely to the presence of flesh in the animal. For instance, lower limb bones sustained the most damage because there was the least amount of flesh shielding the bones at those locations. The concretions formed as the flesh chemically reacted to the seafloor on the largest parts of the animal where the scavenging mosasaur would be unable to fully wrap its jaws around the carcass. Bones pulled free from the carcass were buried in the mud and preserved in mudstone. The organisms occurring with the Talkeetna Mountains hadrosaur fit the description of the second of three types of benthic communities identified by Hogler as forming around large reptile carcasses that would eventually fossilize.
species Tylosaurus proriger.
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
strata
Stratum
In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...
exposed in the northern Chugach Mountains
Chugach Mountains
The Chugach Mountains of southern Alaska are the northernmost of the several mountain ranges that make up the Pacific Coast Ranges of the western edge of North America. The range is about 500 km long, running generally east-west. Its highest point is Mount Marcus Baker, at , but most of its...
, Matanuska Valley, and southern Talkeetna Mountains
Talkeetna Mountains
The Talkeetna Mountains are a mountain range in Alaska. The Matanuska and Susitna River valleys, with towns such as Trapper Creek, Talkeetna, Wasilla, Palmer, Sutton, and Chickaloon, roughly bound the Talkeetnas in the westerly parts of the range. Sovereign Mountain rises to 8849 feet in the...
of South-Central Alaska
Alaska
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
. The Matanuska Formation contains strata from Early Cretaceous (Albian) to Late Cretaceous (Maestrichtian). Parts of the formation contain abundant marine mollusks
Mollusca
The Mollusca , common name molluscs or mollusksSpelled mollusks in the USA, see reasons given in Rosenberg's ; for the spelling mollusc see the reasons given by , is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. Mollusca is the largest...
, foraminifera
Foraminifera
The Foraminifera , or forams for short, are a large group of amoeboid protists which are among the commonest plankton species. They have reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net...
, and radiolaria
Radiolarian
Radiolarians are amoeboid protozoa that produce intricate mineral skeletons, typically with a central capsule dividing the cell into inner and outer portions, called endoplasm and ectoplasm. They are found as zooplankton throughout the ocean, and their skeletal remains cover large portions of the...
. Fossils of non-marine plants are found in some beds. Fossils of two dinosaurs have been recovered from marine mudstones in the formation. The lower Matanuska Formation (MF) is several hundred meters thick and includes non-marine and marine sediments. Campanian-Maastrichtian graded sandstone, conglomerate, and mudstone comprise the upper 2000 meters of the Formation.
Annelida
Calcareous worm tube fossils are known from the formation.| Annelid Annelid The annelids , formally called Annelida , are a large phylum of segmented worms, with over 17,000 modern species including ragworms, earthworms and leeches... s reported from the Matanuska Formation |
||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | |
Planolites Planolites Planolites is an ichnogenus found throughout the Phanerozoic. Planolites are trace fossils made during the feeding process of ancient wormlike animals.... |
Indeterminate |
|||||
Bivalves
| Bivalves reported from the Matanuska Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
Acila |
A. (Truncacila) sp. |
 |
||||
Inoceramus Inoceramus Inoceramus is an extinct genus of fossil marine pteriomorphian bivalves that superficially resembled the related winged pearly oysters of the extant genus Pteria.... |
I. cuvieri |
|||||
I. hobetsensis |
||||||
I. mamatensis |
||||||
I. teshioensis |
||||||
Nucula Nucula Nucula is a genus of clams of the family Nuculidae.-Species:* Nucula aegeensis Jeffreys, 1879 - Aegean nutclam* Nucula annulata Hampson, 1971 * Nucula atacellana Schenck, 1939 - cancellate nutclam... |
Indeterminate |
|||||
Teredolites Teredolites Teredolites is an ichnogenus of trace fossil.-External links:*... |
Indeterminate |
|||||
Cephalopods
| Cephalopod Cephalopod A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot... s reported from the Matanuska Formation |
||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | |
Eubostrychoceras Eubostrychoceras Eubostrychoceras is a genus of helically wound, corkscew form, heteromorph ammonite which lived during the Upper Cretaceous . The genus is included in the ancycleratid family Nostoceratidae.... |
E. japonicum |
|||||
Gaudryceras |
G. denseplicatum |
|||||
Mesopusozia |
M. indopacifica |
|||||
Muramotoceras Muramotoceras Muramotoceras was an unusual genus of heteromorphic ammonite. It was known only from Japan until researchers reported in 2001 that the genus was present in Alaska's Matanuska Formation as well. Its remains likely date to the middle Turonian in both areas.... |
M. yezoense |
|||||
Otoscaphites |
O. teshioensis |
Synonym of Yezoites Yezoites Yezoites is an extinct genus of cephalopod belonging to the Ammonite subclass.... . |
||||
Sciponoceras |
Indeterminate |
|||||
Tetragonites |
T. glabrus |
|||||
Yezoites Yezoites Yezoites is an extinct genus of cephalopod belonging to the Ammonite subclass.... |
Y. puerculus |
|||||
Cnidarians
| Cnidarians reported from the Matanuska Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | |
Platycanthus |
Indeterminate |
Small solitary hexacoral. |
||||
Gastropods
An unidentified naticid snail is known from the formation.| Gastropods reported from the Matanuska Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | |
Biplica |
Indeterminate |
Opisthobranch |
||||
Scaphopods
| Scaphopods reported from the Matanuska Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | |
Dentalium Dentalium The word dentalium or dentalia , as commonly used by Native American artists and anthropologists, refers to tooth shells or tusk shells used in indigenous jewelry, adornment, and commerce in western Canada and the United States. These tusk shells are a kind of seashell, specifically the shells of... |
Indeterminate |
|||||
Dinosaurs
Hadrosaurid
Hadrosaurids or duck-billed dinosaurs are members of the family Hadrosauridae, and include ornithopods such as Edmontosaurus and Parasaurolophus. They were common herbivores in the Upper Cretaceous Period of what are now Asia, Europe and North America. They are descendants of the Upper...
was found in the Matanuska Formation. Its discovery heralded the knowledge of a new high-latitude source of dinosaur fossils. This was the first occurrence of a hadrosaur in south-central Alaska, one out of only four vertebrate fossils from the entire Wrangellia Composite Terrane, and the first associated skeleton of an individual dinosaur in Alaska. The carcass appeared to have been deposited in a bathyal or outer shelf environment. Scavenged bones are preserved in soft 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...
while intact bones were presevered in calcareous
Calcareous
Calcareous is an adjective meaning mostly or partly composed of calcium carbonate, in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.-In zoology:...
concretions. Some calcareous concretions may be the result of pieces of meat falling off as the carcass disintegrated. The hadrosaurid was a geographic link between the hadrosaurs of north america and asia.
The "Talkeetna Mountains Hadrosaur" specimen was discovered in 1994
1994 in paleontology
-Dinosaurs:* Aff. Rebbachisaurus gastroliths documented.* The "Talkeetna Mountains Hadrosaur" specimen was discovered in a quarry being excavated for road material. The quarry is near the Glenn Highway, approximately 150 miles northeast of Anchorage...
in a quarry being excavated for road material. That fall, excavation began, and was resumed in the summer of 1996
1996 in paleontology
-Newly named crustaceans:-Dinosaurs:* In the summer excavation resumed on the Talkeetna Mountains Hadrosaur, discovered in a quarry near the Glenn Highway, approximately 150 miles northeast of Anchorage.-Newly named dinosaurs:...
. The specimen is housed at the University of Alaska Museum. The quarry is near the Glenn Highway
Glenn Highway
-References:* Pasch, A. D., K. C. May. 2001. Taphonomy and paleoenvironment of hadrosaur from the Matanuska Formation in South-Central Alaska. In: Mesozioc Vertebrate Life. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press. Pages 219-236.-External links:**...
, approximately 150 miles northeast of Anchorage. The layer consists of dark grey marine mudstone that weathers easily. The mudstone contains highly indurated calcareous concretions and finely disseminated pyrite
Pyrite
The mineral pyrite, or iron pyrite, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale-to-normal, brass-yellow hue have earned it the nickname fool's gold because of its resemblance to gold...
crystals. Fresh wet surface display horizontal lamina, ripples and evidence of bioturbation
Bioturbation
In oceanography, limnology, pedology, geology , and archaeology, bioturbation is the displacement and mixing of sediment particles and solutes by fauna or flora . The mediators of bioturbation are typically annelid worms , bivalves In oceanography, limnology, pedology, geology (especially...
. Evidence that these strata have experienced deformation
Deformation
In materials science, deformation is a change in the shape or size of an object due to an applied force or a change in temperature...
after deposition include "joint sets, faults, secondary deposition of calcite, and degree of induration."
The strata's foraminiferans and mollusks all point to a middle Turonian
Turonian
The Turonian is, in the ICS' geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.5 ± 0.8 Ma and 89.3 ± 1 Ma...
age for the formation
Geologic formation
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
. Muramotoceras
Muramotoceras
Muramotoceras was an unusual genus of heteromorphic ammonite. It was known only from Japan until researchers reported in 2001 that the genus was present in Alaska's Matanuska Formation as well. Its remains likely date to the middle Turonian in both areas....
is an unusual heteromorph previously known only from Japan. It is also middle Turonian. Eubostrychoceras
Eubostrychoceras
Eubostrychoceras is a genus of helically wound, corkscew form, heteromorph ammonite which lived during the Upper Cretaceous . The genus is included in the ancycleratid family Nostoceratidae....
is known from Japan, Germany, and Madagascar. E. japonicum is Turonian, and likely confined to the middle Turonian. The authors reported teleost tooth and jaw fragments as well as wood fragments from the formation. Other Matanuska fossils include scaphopods, foraminifera, and palynomorphs. The quarry belongs to the lower region of C-1, an informal stratigraphic unit, and Member Four.
The "Talkeetna Mountains Hadrosaur" was an juvenile animal about 3 m (10 feet) long. The bones of the forelimbs with partial manus and ribs have been positively identified, as have most of the tail vertebrae Pelvis and dorsal vertebrae tentatively identified. The specimen could not be distinguished as a hadrosaurid or lambeosaurid. Aspects of its anatomy greatly differed from Edmontosaurus
Edmontosaurus
Edmontosaurus is a genus of crestless hadrosaurid dinosaur. It contains two species: Edmontosaurus regalis and Edmontosaurus annectens. Fossils of E. regalis have been found in rocks of western North America that date from the late Campanian stage of the Cretaceous Period 73 million years ago,...
.
The thin shelled heteromorphic ammonites probably lived at depths 36–183 m. Inoceramids tended to be at upper bathyal and neritic environments. The pyrite around the animal may have been the result of sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
produced by bacteria consuming the carcass. Invertebrate shells lie parallel to bedding. The high quality of the invertebrate fossils and their lack of any sign of biological action on the part of encrusting or boring
Boring
Boring often refers to anything that causes boredom.Boring may also refer to:Making holes*Boring , the drilling of holes or tunnels in the earth**Tunnel boring machine machine used in boring tunnels or shafts...
invertebrates suggest that there weren't many animals in the environment and only arrive at the location after dying. It is possible that mudslides could have transported the shells to the location, meaning that the preserved collection of species might not represent a specific ecosystem
Ecosystem
An ecosystem is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving , physical components of the environment with which the organisms interact, such as air, soil, water and sunlight....
. It may have also been possible for dead ammonites to float long distances. Heteromorphic ammonites probably didn't drift as far due to their potentially benthic mode of life or the septum
Septum
In anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...
closing off the living chamber not being calcified and decomposing after death. The most abundant mollusks in the quarry are inoceramids. The ecological context indicates that the "Talkeetna Mountains Hadrosaur" was buried at a depth greater than 35 m.
The skull fell off before the carcass sank. The body came to rest on its left side with limbs extended to the east. About 20% of the hadrosaur's bones were envloped by calcareous concretions. There were 20 concretions recovered. Every element not found in a concretion bore many closely spaced ovualar conical depressions ranging in diameter from 2.12 to 5.81 mm and 1.64 to 3.62 deep. The depressions are probably bite marks. The depressions are not symmetrical enough for gastropod drill marks and are not shaped like sponge borings. None of the preserved fish fossils of the formation fit the size or geometry of the borings. The size and spacing and shape by contrast resembles closeley the teeth of the mosasaur
Mosasaur
Mosasaurs are large extinct marine lizards. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764...
species Tylosaurus proriger. If the damage to the body had been done prior to being washed out to sea, it likely would have punctured the body, preventing the build up of bloating gases that allowed the carcass to drift out to sea in the first place. The distribution of bite marks corresponds inversely to the presence of flesh in the animal. For instance, lower limb bones sustained the most damage because there was the least amount of flesh shielding the bones at those locations. The concretions formed as the flesh chemically reacted to the seafloor on the largest parts of the animal where the scavenging mosasaur would be unable to fully wrap its jaws around the carcass. Bones pulled free from the carcass were buried in the mud and preserved in mudstone. The organisms occurring with the Talkeetna Mountains hadrosaur fit the description of the second of three types of benthic communities identified by Hogler as forming around large reptile carcasses that would eventually fossilize.
Lizards
Every element of the Talkeetna Mountains Hadrosaur specimen that was not found in a concretion bore many closely spaced ovualar conical depressions ranging in diameter from 2.12 to 5.81 mm and 1.64 to 3.62 deep. These depressions are probably bite marks. The depressions are not symmetrical enough for gastropod drill marks and are not shaped like sponge borings. None of the preserved fish fossils of the formation fit the size or geometry of the borings. The size and spacing and shape by contrast resembles closeley the teeth of the mosasaurMosasaur
Mosasaurs are large extinct marine lizards. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764...
species Tylosaurus proriger.
Palynomorphs
- Lycopodophyta: One Species
- Pteridophyta: Sixty-Nine Species
- Ginkgophyta: Nine Species
- Cycadophyta: Nine Species
- Pinophyta: Nine Species
- Anthophyta: Five Species