Hornerstown Formation | |
---|---|
Stratigraphic range: latest Maastrichtian-Danian [1] | |
Type | Geological formation |
Unit of | Rancocas Group |
Underlies | Vincentown Formation |
Overlies | New Egypt Formation, Navesink Formation and Tinton Formation |
Lithology | |
Primary | Marl, greensand |
Location | |
Region | New Jersey |
Country | United States |
Type section | |
Named for | Hornerstown, New Jersey |
The Hornerstown Formation is a latest Cretaceous to early Paleocene-aged geologic formation in New Jersey. It preserves a variety of fossil remains, including those of dinosaurs, and contains direct evidence of the mass mortality that occurred at the Cretaceous-Paleogene boundary. [2] [3] [4]
Outcrops of the Hornerstown Formation are known from sites such as Edelman Fossil Park. [5]
The age of the Hornerstown deposits have been controversial. While most fossils are of animal taxa known from the earliest Cenozoic era, several fossils of otherwise exclusively Cretaceous age have been found. These include remains of the shark Squalicorax , several types of non-avian dinosaurs, the teleost fish Enchodus , several species of ammonite, and marine lizards referred to the genus Mosasaurus . Some of these remains show signs of severe abrasion and erosion, however, implying that they may be re-worked from older deposits. Most of these fossils are restricted to the lowest point in the formation, one rich in fossils and known as the Main Fossiliferous Layer, or MFL. Other explanations for the out-of-place fossils in the MFL is that they represent a time-averaged assemblage that built up and remained unburied during a time of low sediment deposition, or that they were stirred up from deeper in the sediment and deposited together during a tsunami. [6] Biochemical analyses done on mosasaur bones from the Hornerstown Formation and the underlying, purely Cretaceous New Egypt Formation have found differing chemical signatures in the content of rare earth elements depending on whether the bones derive from the New Egypt or the Hornerstown Formation. This provides evidence against the idea that the presence of these remains in the Hornerstown is just the result of reworking, and supports the Hornerstown Formation including Cretaceous strata. [7]
To account for these Cretaceous fossils, the Hornerstown Formation is generally treated as including the last portion of the Maastrichtian shortly before the Cretaceous-Paleogene boundary, and is thus divided into three sections: the section below the MFL (entirely Maastrichtian), the MFL itself (at the K-Pg boundary), and the section above the MFL (entirely Danian). However, other studies continue to treat the Hornerstown Formation as a Paleocene formation that saw significant reworking of Cretaceous fossils into itself. [8] In addition, recent studies have found evidence of high iridium concentration and shocked quartz within the MFL, suggesting that the MFL represents a thanatocoenosis formed from an ecosystem collapse during the Cretaceous-Paleogene extinction event. This makes the Hornerstown Formation one of the few geological formations to contain direct evidence of the immediate impact of the extinction event. The Hornerstown Formation is important paleontologically, as it shows the impact of the K-Pg extinction on the coastal waters of eastern Appalachia, contains many of the last known records of taxa that went extinct at the K-Pg boundary, while also providing evidence of survivorship for the taxa that managed to survive the extinction event. [3]
Based on Case (1996) and Boles et al (2024): [3] [9]
Chimaeras of the Hornerstown Formation | ||||||||
---|---|---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Abundance | Material | Notes | Images | |
Edaphodon | E. agassizi | Danian | Tooth plates | A callorhinchid chimaera. | ![]() | |||
E. mantelli | Danian | |||||||
E. mirificus | Maastrichtian | |||||||
E. stenobyrus | Maastrichtian | |||||||
Ischyodus | I. bifurcatus | Maastrichtian, potentially Danian | Tooth plates, jaw elements | A callorhinchid chimaera. | ![]() | |||
I. thurmanni | Maastrichtian | |||||||
I. williamsae | Danian |
Sharks of the Hornerstown Formation | ||||||||
---|---|---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Abundance | Material | Notes | Images | |
Araloselachus | A. cuspidatus | Maastrichtian | Teeth | A sand shark. [10] | ![]() | |||
Carcharias | C. teretidens | Danian | A relative of the sand tiger shark. | ![]() | ||||
Cretalamna | C. appendiculata | Maastrichtian & Danian | A megatooth shark. | ![]() | ||||
Heptranchias | H. howellii | Maastrichtian | A relative of the sharpnose sevengill shark. | ![]() | ||||
Hexanchus | H. microdon | Danian | A sixgill shark. | ![]() | ||||
H. sp. | Maastrichtian & Danian | |||||||
Otodus | O. obliquus | Danian | A megatooth shark. | ![]() | ||||
Odontaspis | O. sp. | Danian | A sand shark. | ![]() | ||||
Palaeocarcharodon | P. sp. | Danian | A megatooth shark. | ![]() | ||||
Palaeogaleus | P. vincenti | Maastrichtian & Danian | A houndshark. | ![]() | ||||
Palaeohypotodus | P. rutoti | Danian | A sand shark. | ![]() | ||||
Pseudocorax | P. affinis | Maastrichtian | A pseudocoracid shark. | ![]() | ||||
Scapanorhynchus | S. texanus | Maastrichtian | A goblin shark. [11] | ![]() | ||||
Scyliorhinus | S. gilberti | Danian | A catshark. | ![]() | ||||
Sphenodus | S. lundgreni | Maastrichtian | A orthacodontid shark. | ![]() | ||||
Squalicorax | S. pristodontus | Maastrichtian | A crow shark. | ![]() | ||||
Squalus | S. minor | Maastrichtian & Danian | A spurdog. | ![]() | ||||
S. sp | ||||||||
Squatina | S. sp. | Maastrichtian | An angelshark. | ![]() | ||||
Weltonia | W. ancistrodon | Danian | A cow shark. | |||||
Xampylodon | X. brotzeni | Maastrichtian | A cow shark. | ![]() |
Rays of the Hornerstown Formation | ||||||||
---|---|---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Abundance | Material | Notes | Images | |
Aetomylaeus | A. striatus | Maastrichtian | Teeth | An eagle ray. [10] | ![]() | |||
Dasyatis | D. crosswickense | Danian | A whiptail stingray. Type locality for species. | ![]() | ||||
Hypolophites | H. hutchinsi | Danian | A whiptail stingray. Type locality for species. | |||||
Hypolophodon | H. sylvestris | Danian | A whiptail stingray. | |||||
Ischyrhiza | I. mira | Maastrichtian | A sclerorhynchid sawskate. [10] | ![]() | ||||
Rhinoptera | R. sp. | Maastrichtian | A cownose ray. | ![]() | ||||
Rhombodus | R. laevis | Maastrichtian | A rhombodontid ray. | ![]() | ||||
Viperecucullus | V. kuehnei | Danian | A whiptail stingray, type locality for the species and genus. |
Actinopterygii of the Hornerstown Formation | ||||||||
---|---|---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Abundance | Material | Notes | Images | |
Acipenser | A. cf. albertensis | Maastrichtian | A sturgeon. [3] | ![]() | ||||
Anomoeodus | A. phaseolus | Maastrichtian, potentially Danian | 8 teeth | A pycnodont. One tooth is known from the Danian section of the formation, which would be the latest record of this genus and prove its occurrence in the Cenozoic; however, it may have been reworked from lower layers. [3] | ![]() | |||
Atractosteus | A. sp. | Maastrichtian & Danian | 11 teeth | A gar. First record of gars from eastern North America during the Paleocene. [3] | ![]() | |||
cf. Bananogmius | cf. B. sp. | Maastrichtian | A plethodid tselfatiiform. [3] [10] | ![]() | ||||
Dercetidae indet. | Maastrichtian & Danian | 27 flank scales | A dercetid aulopiform. The first evidence in eastern North America of the Dercetidae surviving the K-Pg extinction event. [3] | |||||
Enchodus | E. ferox | Maastrichtian | An enchodontid aulopiform. The E. gladiolus remains are the first record of the species in eastern North America. [3] | ![]() | ||||
E. gladiolus | 8 teeth | |||||||
Iridopristis | I. parrisi | Sewell, New Jersey | Danian | 3 partial articulated specimens, including a near-complete skull. [8] | A stem-lineage member of Holocentridae. The earliest known definitive holocentrid. Type locality for genus and species. [8] | |||
Paralbula | P. marylandica | Maastrichtian & Danian | 23 teeth | A phyllodontid elopomorph. First evidence of P. marylandica existing during the Cretaceous, indicating that it survived the extinction event. [3] | ||||
Phyllodus | P. paulkatoi | Maastrichtian | 1 tooth plate | A phyllodontid elopomorph. First known occurrence in eastern North America. [3] | ||||
Saurocephalus | S. lanciformis | Danian | 1 tooth | A saurodontid ichthyodectiform. First known occurrence in eastern North America and first known occurrence of ichthyodectiforms as a whole in the Paleocene and Cenozoic. [3] | | |||
A number of fossil birds are known from the greensands of the formation. The Hornerstown serves as the type locality for all these genera and species:
Birds of the Hornerstown Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Abundance | Notes | |
A. rex | ?earliest Paleocene [12] [13] | A waterfowl potentially related to the magpie-goose. [3] [14] | ||||
G. velox | A potential wader. [3] [14] | |||||
L. edwardsianus | A laornithid wading bird. [3] [14] | |||||
Novacaesareala | N. hungerfordi | A potential tropicbird. [3] [14] | ||||
P. littoralis | A potential wader. [3] [14] | |||||
P. vagans | ||||||
T. priscus | A potential wader. [3] [14] | |||||
T. glauconiticus | A potential seabird. [3] [14] | |||||
Dinosaurs of the Hornerstown Formation | ||||||
---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Abundance | Notes | |
Hadrosauridae indet. | Maastrichtian | A hadrosaurid ornithischian. [3] | ||||
The tyrannosauroid Dryptosaurus is sometimes referred to this formation, as its remains were found in the New Egypt Formation, which is sometimes considered a part of the Hornerstown. [15]
Crocodylomorphs of the Hornerstown Formation | ||||||||
---|---|---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Abundance | Material | Notes | Images | |
Borealosuchus | B. threeensis | Maastrichtian | Lower jaw, postcranial remains | A eusuchian. Type locality of species. [3] [16] | ![]() | |||
B. harlani | Maastrichtian & Danian | Remains including lower jaw of a juvenile individual [17] | An early caiman. [3] [17] | |||||
B. tuberculatus [10] | Maastrichtian | |||||||
Hyposaurus | H. rogersii | Maastrichtian & Danian | A dyrosaurid. [3] [18] | |||||
cf. Procaimanoidea | P. sp. | Maastrichtian | A caiman. [3] | ![]() | ||||
Thoracosaurus | T. neocesariensis | Maastrichtian & Danian | A gavialoid. [3] | ![]() |
Plesiosaurs of the Hornerstown Formation | ||||||||
---|---|---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Abundance | Material | Notes | Images | |
" Plesiosaurus " | "P." brevifemur | Maastrichtian | An indeterminate plesiosaur known from a well-documented specimen, now lost. [19] [20] |
Testudines of the Hornerstown Formation | |||||||
---|---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Abundance | Notes | Images | |
Adocus | A. agilis [19] | Maastrichtian | An adocid. [3] | ![]() | |||
A. beatus | |||||||
A. syntheticus [19] | |||||||
Agomphus | A. pectoralis | Maastrichtian | A kinosternoid related to Dermatemys . [3] [21] | ![]() | |||
Bothremys | B. sp. | Maastrichtian | A bothremydid side-necked turtle. [3] | ||||
Euclastes | E. wielandi | Maastrichtian & Danian | A sea turtle. [3] | ![]() | |||
Lytoloma | L. jeanesii | Maastrichtian | A sea turtle. [19] | ||||
Osteopygis | O. emarginatus | Maastrichtian | A macrobaenid. [19] | ||||
Peritresius | P. ornatus | Maastrichtian | A sea turtle. | ||||
Taphrosphys | T. sulcatus | Maastrichtian | A bothremydid side-necked turtle. [3] | ||||
T. strenuus |
Mosasaurs of the Hornerstown Formation | ||||||||
---|---|---|---|---|---|---|---|---|
Genus | Species | Location | Stratigraphic position | Abundance | Material | Notes | Images | |
Halisaurus | H. platyspondylus | Maastrichtian | A halisaurine. Type locality of the genus and species. | ![]() | ||||
Mosasaurus | M. hoffmanni (=Nectoportheus validus) [19] | Maastrichtian | Pterygoid, teeth, vertebrae [3] [7] | A mosasaurine. This formation contains some of the last known remains, comprising individuals killed during the mass mortality event that formed the MFL. [3] A very large specimen is known. [7] | ![]() | |||
Plioplatecarpus | P. sp. | Maastrichtian | A plioplatecarpine. | ![]() |
Cimolomys is a mammal genus from the Upper Cretaceous of North America. It was a member of the extinct order Multituberculata within the suborder Cimolodonta and family Cimolomyidae.
The Late Cretaceous is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after creta, the Latin word for the white limestone known as chalk. The chalk of northern France and the white cliffs of south-eastern England date from the Cretaceous Period.
Coriops is an extinct genus of freshwater osteoglossomorph fish, possibly a hiodontiform, with a single species known from the Late Cretaceous of western North America.
Euclastes is an extinct genus of sea turtles that survived the Cretaceous–Paleogene mass extinction. The genus was first named by Edward Drinker Cope in 1867, and contains three species. E. hutchisoni, was named in 2003 but has since been reassigned to the genus Pacifichelys, while E. coahuilaensis named in 2009 was reassigned as Mexichelys coahuilaensis in 2010.
The Lopez de Bertodano Formation is a geological formation in the James Ross archipelago of the Antarctic Peninsula. The strata date from the end of the Late Cretaceous to the Danian stage of the lower Paleocene, from about 70 to 65.5 million years ago, straddling the Cretaceous-Paleogene boundary.
Bottosaurus is an extinct genus of alligatorid from the Late Cretaceous-Early Paleocene of New Jersey, Texas, and possibly North Carolina and South Carolina. Two species are currently accepted, with a third requiring re-evaluation.
The Navesink Formation is a 66 to 70 mya greensand glauconitic marl and sand geological formation in New Jersey. It is known for its Cretaceous period fossil shell beds and dinosaur bones.
Ampheristus is an extinct genus of prehistoric marine ray-finned fish. It was a basal or stem member of the family Ophidiidae, which contains modern cusk-eels. Fossils are known from worldwide from the Late Cretaceous to the late Paleogene, making it a rather successful survivor of the Cretaceous-Paleogene extinction event.
Anomoeodus is an extinct genus of prehistoric marine ray-finned fish belonging to the family Pycnodontidae. This genus primarily lived during the mid-to-late Cretaceous period, ranging from the Albian to the very end of the Maastrichtian age, and possibly into the Danian. The first fossils of Anomoeodus were described by Louis Agassiz in 1833, although they were described under Pycnodus. Some studies have recovered it as a wastebasket taxon.
The Intertrappean Beds are a Late Cretaceous and early Paleogene geologic unit in India. These beds are found as interbeds between Deccan Traps layers, including the slightly older Lameta Formation. They consist a number of different subgroups and formations, and span the Cretaceous–Paleogene boundary.
The Marshalltown Formation is a Late Cretaceous (Campanian)-aged geologic formation in New Jersey and Delaware, US. Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation. It contains the most extensive Campanian-aged dinosaur fauna from New Jersey and Delaware.
The Moreno Formation is a Mesozoic geologic formation located in San Joaquin Valley (California).
Dinosaur remains diagnostic to the genus level are among the fossils that have been recovered from the formation.
During most of the Late Cretaceous the eastern half of North America formed Appalachia, an island land mass separated from Laramidia to the west by the Western Interior Seaway. This seaway had split North America into two massive landmasses due to a multitude of factors such as tectonism and sea-level fluctuations for nearly 40 million years. The seaway eventually expanded, divided across the Dakotas, and by the end of the Cretaceous, it retreated towards the Gulf of Mexico and the Hudson Bay.
The Oulad Abdoun Basin is a phosphate sedimentary basin located in Morocco, near the city of Khouribga. It is the largest in Morocco, comprising 44% of Morocco's phosphate reserves, and at least 26.8 billion tons of phosphate. It is also known as an important site for vertebrate fossils, with deposits ranging from the Late Cretaceous (Maastrichtian) to the Eocene epoch (Ypresian), a period of about 25 million years.
The New Egypt Formation is a Late Cretaceous geologic formation of the Monmouth Group in New Jersey, United States.
The Peedee Formation is a geologic formation in North and South Carolina. A marine deposit representing an inner neritic environment, named for exposures along the Great Peedee River, it preserves invertebrate and vertebrate fossils dating to the Late Cretaceous (Maastrichtian).
The Cretaceous–Paleogene (K–Pg) extinction event, also known as the K–T extinction, was the mass extinction of three-quarters of the plant and animal species on Earth approximately 66 million years ago. The event caused the extinction of all non-avian dinosaurs. Most other tetrapods weighing more than 25 kg (55 lb) also became extinct, with the exception of some ectothermic species such as sea turtles and crocodilians. It marked the end of the Cretaceous period, and with it the Mesozoic era, while heralding the beginning of the current era, the Cenozoic. In the geologic record, the K–Pg event is marked by a thin layer of sediment called the K–Pg boundary, Fatkito boundary or K–T boundary, which can be found throughout the world in marine and terrestrial rocks. The boundary clay shows unusually high levels of the metal iridium, which is more common in asteroids than in the Earth's crust.
The term Paleocene ammonites describes families or genera of Ammonoidea that may have survived the Cretaceous–Paleogene extinction event, which occurred 66.043 million years ago. Although almost all evidence indicated that ammonites did not survive past the K–Pg boundary, there is some scattered evidence that some ammonites lived for a short period of time during the Paleocene epoch, although none survived the Danian ; they were likely extinct within 500,000 years of the K-Pg extinction event, which correlates to roughly 65.5 Ma. The evidence for Paleocene ammonoids is rare and remains controversial.
Cyclurus is an extinct genus of freshwater amiid ray-finned fish known from the Late Cretaceous to the Early Oligocene across much of the Northern Hemisphere. It is thought to be the closest relative of the extant bowfins in the genus Amia, although species of Cyclurus were significantly smaller in size compared to Amia.