Csehbánya Formation

The Csehbánya Formation is a geological formation in the Transdanubian Mountains of Veszprém County, Hungary. The formation dates to the Late Santonian (around 85-84 million years ago) of the Late Cretaceous. It represents a floodplain environment as opposed to the swampy lacustrine environment of the simultaneous Ajka Coal Formation, though there is complete overlap in terms of fauna. It underlies the Jákó Marl Formation, and laterally transitions to the Ajka Coal Formation.^[1]

Csehbánya Formation
Stratigraphic range: Late Santonian, ~85–84 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Type	Geological formation
Underlies	Jákó Marl Formation, localized unconformity with Eocene Iharkút Conglomerate present in some areas
Overlies	Unconformity with Upper Triassic Main Dolomite Formation and Upper Cretaceous Nagytárkány Bauxite Formation
Area	Transdanubian Mountains
Thickness	Varies, but up to 100–150 m (330–490 ft)
Lithology
Primary	Siltstone, sandstone conglomerate
Other	Claystone
Location
Coordinates	47.24°N 17.64°E / 47.24; 17.64
Approximate paleocoordinates	31.0°N 18.6°E / 31.0; 18.6
Region	Europe
Country	Hungary
Type section
Named for	Csehbánya, Hungary
Csehbánya Formation (Hungary)

Stratigraphy of the Iharkút locality

Geology

The lithology of the unit is a cyclic variation of conglomerate, sandstone, variegated siltstone, clay and marl layers with some sporadic thin coal seams.^[2] It is unconformably overlies the Late Triassic Main Dolomite Formation, which has deposits of the Upper Cretaceous Nagytárkány Bauxite Formation within deep karstic sinkholes in the formation. There is a basal conglomerate of dolomite clasts at the base of the Csehbánya formation. The main exposed portion of the formation is called the Iharkút locality, which is a disused bauxite quarry. At this location due to Paleogene uplift, it is unconformably overlain by the Lutetian Ikharkút Conglomerate. In the upper levels of the formation, there are sandstone lens beds present, which represent channel bodies. These are indicative of an anastomosing fluvial system. The exposure at this locality is between 100–150 m. Most of the fossils are found within the SZ-6 site at the locality, which is interpreted as a lag channel deposit

Invertebrate paleofauna

Amber is known from both the Ajka Coal and Csehbánya Formations, and is commonly referred to as ajkait. However most of the arthropod inclusions in these are undescribed, only being shown in photographs,^[3] with only two species of Ceratopogonids (biting midges) in the extant genus Leptoconops and the extinct genus Adelohelea being described.^[4] A list of known taxa is given below.

Invertebrates
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Adelohelea	A. magyarica				Biting midge
Leptoconops	L. clava				Biting midge, genus currently extant
Coleoptera	Indeterminate
Diptera	Indeterminate
Hymenoptera	Indeterminate
Nematocera	Indeterminate

Vertebrate paleofauna

Various fossils from the Csehbánya Formation

Fishes, amphibians, turtles, squamates, crocodilians, dinosaurs^[5] and pterosaurs present in Veszprém, Hungary, near the village of Németbánya in the Iharkút locality, an open-pit bauxite mine.^[6][7] Other finds include Abelisauridae indet.,^[8] Rhabdodontidae indet.,^[7] Tetanurae indet.^[8] Coprolites^[9] and eggshells^[10] are also known from the locality.

Fish

Fish[11]
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Atractosteus	Indeterminate	Iharkút locality		"Jaw fragments, teeth, scales, vertebrae"	Gar, genus extant
Coelodus	Indeterminate			Possible dentary/premaxilla, vomers, prearticulars, teeth and possible scales[12]	Pycnodontiform
Vidalamiinae	Indeterminate			"Two vertebrae"
Amiidae	Indeterminate			A left anterior ceratohyal and a vertebra
Elopiformes	Indeterminate			13 vertebrae
Ellimmichthyiformes	Indeterminate			At least two distinct taxa represented by four and one vertebrae	Clupeimorph
cf. Salmoniformes	Indeterminate			two vertebrae
Acanthomorpha	Indeterminate			Three vertebrae and 18 fin spines
Teleostei	Indeterminate			Teeth, vertebrae and cycloid scales
Actinopterygii	Indeterminate			9 distinct teeth morphotypes and some teeth bearing elements

Amphibians

Amphibians
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Albanerpeton[13]	Indeterminate	Iharkút locality		Skull and jaw elements	Albanerpetontid
Bakonybatrachus[14]	B. fedori	Iharkút locality		Pelvic elements	Discoglossid frog
Hungarobatrachus[15]	H. szukacsi	Iharkút locality		Pelvic elements	Advanced frog
Palaeobatrachidae	Indeterminate	Iharkút locality		Postcranial remains
Pelobatidae	Indeterminate	Iharkút locality		Postcranial remains

Squamates

Squamates
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Bicuspidon	B. aff. hatzegiensis[16]			Fragmentary mandibles, maxillae	Polyglyphanodontid
Chromatogenys[17]	C. tiliquoides			Partial right mandible	Scincomorph
Distortodon[18]	D. rhomboideus			Dentaries, maxilla	Polyglyphanodontid
Pannoniasaurus[19]	P. inexpectatus			Partial skeleton	Mosasaur, also known from Ajka Coal Formation[1]
Pelsochamops[20]	P. infrequens			Fragmentary dentary, dentary fragments	Chamopsiid
Scincomorpha[21]	Indeterminate			Fragmentary dentaries	At least 3 distinct taxa, 4 mentioned in paper, but unsure if this counts Chromatogenys

Crocodyliformes

Crocodyliformes of the Csehbánya Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Iharkutosuchus[22]	I. makadii			"Complete and partial skulls, mandibles, various cranial elements, teeth"	Hylaeochampsid
Doratodon[23]	D. carcharidens			"Teeth, Jaw fragment"
?Theriosuchus	Indeterminate			"Teeth, cranial elements"
?Allodaposuchus	Indeterminate			"Teeth, jaw fragments, cranial elements"

Turtles

Turtles of the Csehbánya Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Foxemys	F. trabanti			"Complete and partial skulls, mandibles, vertebrae, pectoral and pelvic girdle elements, limb bones, plastron and carapax fragments"
Kallokibotion	Indeterminate			Shell fragments
Dortokidae	Indeterminate			Shell fragments

Pterosaurs

Pterosaurs of the Csehbánya Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Bakonydraco [24]	B. galaczi	Veszprém		"Premaxilla, complete mandible, 56 mandibular symphyses"	Tapejarid
Azdarchidae	Indeterminate			"Cervical vertebrae, pelvic girdle elements, limb bones"
Pterodactyloidea	Indeterminate			"3 mandibular symphyses"

Dinosaurs

Dinosaurs of the Csehbánya Formation
Genus	Species	Location	Stratigraphic position	Abundance	Notes	Images
Ajkaceratops[25]	A. kozmai[25]			Fused premaxillae and rostral bones, with fragments of the maxillae, four predentaries.[25] Referred teeth.[26]	Ornithischian, possibly a ceratopsian
Bauxitornis[27]	B. mindszentyae			Single right tarsometatarsus	Avisaurid enantiornithine
Hungarosaurus[28]	H. tormai	Veszprém		Several partial skeletons	Struthiosaurine nodosaur
Mochlodon	M. vorosi[29]			Partial skull and postcrania	Rhabdodontid
Pneumatoraptor[8]	P. fodori	Veszprém		Single left scapulocoracoid	Paravian
Struthiosaurus	Indeterminate			Humerus[30] and partial hip, and pelvic armor elements.[31]	Struthiosaurine nodosaur
Abelisauridae	Indeterminate			Femur[32] and pedal ungual phalanx[8]
Enantiornithes	Indeterminate			Limb bones
Paraves	Indeterminate			"Teeth, caudals, limb bones"
Sauropoda[33]	Indeterminate			Single tooth
Tetanurae	Indeterminate			More than 50 teeth[8]

See also

• List of dinosaur-bearing rock formations
• List of fossiliferous stratigraphic units in Hungary