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.[2][1]
Many mostly fragmentary fossils, especially of small vertebrates, are known from the formation.[3] Indeterminate theropod and pterosaur remains have been recovered from the formation, as well as dinosaur eggs.[4][5] The mammal genera Deccanolestes, Sahnitherium, Bharattherium, Indoclemensia, Indotriconodon and Kharmerungulatum have been recovered from several localities.[6] The Early Eocene-aged[7] Bamanbor locality in Gujarat preserves articulated freshwater fish specimens.[8][9] A rich plant flora is known from the formation.
Although often thought of as a contemporaneous unit that was formed in a single rapid eruption event, more studies that date the age of the volcanic beds indicate that the Deccan Traps did not erupt all at once. Instead, different portions appear to have erupted during different periods of time. This means that the Intertrappean Beds are best understood as a group of different volcanic-associate formations of varying ages.[10]
Kale et al (2020) divided the group into the following provinces:[10]
- Sahyadri Group or Western Province (age: Late Maastrichtian to Danian, ~67.5 to 62.5 mya)
- Satpura Group or Central Province
- Malwa Group (age: Late Maastrichtian, ~67.7 mya; likely the oldest group)
- Amarkantak Group or Mandla Province (age: early Paleogene, ~64.5 mya - unknown)
Mittal et al (2021) divided the group into the following provinces:[11]
Kale et al (2020) divided the group as follows. Subgroups/formations are classified based on oldest to youngest.[10]
- Wai Subgroup (youngest)
- Desur Formation
- Panhala Formation
- Mahabaleshwar Formation (~63.2 mya)
- Ambenali Formation
- Poladpur Formation
- Lonavala Subgroup
- Bushe Formation
- Khandala Formation
- Kalsubai Subgroup (oldest, ~67.5 mya)
- Bhimashankar Formation
- Thakurwadi Formation
- Neral Formation
- Igatpuri Formation
- Jawhar Formation
Kale et al (2020) divided the group as follows. Subgroups/formations are classified based on oldest to youngest.[10]
- Sahyadri Group:
- Bombay Subgroup (~62.5 mya)
- Borivali Formation
- Elephanta Formation
- Khandala Subgroup (~67.5 to 63.2 mya)
- Mahabaleshwar Formation (~63.2 mya)
- Purandargarh Formation
- Diveghat Formation
- Karla Formation
- Indrayani Formation
- Kalsubai Subgroup (oldest: ~67.5 mya)
- Upper Ratangarh Formation
- Lower Ratangarh Formation
- Salher Formation
- Satpura Group:
- Karanja Formation (youngest)
- Buldhana Formation
- Chikli Formation
- Ajanta Formation
- Upper Ratangarh Formation
- Karanja Formation
- Buldana Formation
- Chikli Formation (oldest)
- Malwa Group:
- Singarchori Formation (youngest)
- Bargonda Formation
- Indore Formation
- Kankaria-Pirukheri Formation
- Kalisindh Formation
- Mandleshwar Formation
- Gaganwara Formation (oldest)
- Amarkantak Group:
- Kuleru Formation (youngest)
- Khamla/Kampla Formation
- Amarwara Formation
- Multai Formation
- Linga Formation
- Pipardehi Formation
- Dhuma Formation
- Mandla Formation (oldest, ~64.4 mya)
Within the newly defined Saurhastra Group (age: Paleocene to early Eocene), the following divisions were found by Patel & Shah (2023):[12]
- Ninama Basin:
- Ninama Limestone (youngest)
- Sukhbhadar Formation (oldest)
- Chotila Basin:
- Bamanbor Formation (youngest)
- Chotila Chert
- Rangpar Formation (oldest)
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Color key
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Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited.
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| Genus
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Species
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Location
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Stratigraphic position
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Material
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Notes
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Images
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| Carteremys
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C. leithii
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Worli Hill
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Early Paleocene[10]
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Carapace, plastron, skull and partial mandible
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A turtle of uncertain affinities.
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| Sankuchemys
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S. sethnai
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Amboli Quarry[23]
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Skull[23]
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A bothremydid turtle.
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| Genus
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Species
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Location
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Stratigraphic position
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Material
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Notes
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Images
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| Bharattherium
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B. bonapartei
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Kisalpuri
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A fragmentary cheek-tooth.
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A sudamericid mammal.
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| Deccanolestes
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D. hislopi
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Naskal microvertebrate site
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Molars, calcanea, astralgi, humerus, ulna.
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A eutherian mammal.
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| D. robustus
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Naskal microvertebrate site
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"Dental material and an astragalus".
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A eutherian mammal.
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| D. narmadensis
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Kisalpuri
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"Isolated rear molar."
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A eutherian mammal.
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| Indoclemensia
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I. naskalensis
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Naskal microvertebrate site[1]
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Right second Molar.
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A eutherian mammal.
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| I. magnus
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Naskal microvertebrate site[1]
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Left second Molar.
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A eutherian mammal.
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| Indotriconodon
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I. magnus
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Kutch[31]
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Single lower Molar.
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A eutriconodont mammal.
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| Kharmerungulatum
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K. vanvaleni
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Kisalpuri[32]
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Isolated right lower molar.
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A eutherian mammal.
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| Sahnitherium
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S. rangapurensis
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Rangapur microvertebrate site[33]
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Upper Molar.
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A eutherian mammal.
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| Genus
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Species
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Location
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Stratigraphic position
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Material
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Notes
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Images
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| Connaroxylon
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C. dimorphum
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Dhagaon, Mandla district[35]
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Wood[35]
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Affinities with Connaraceae.
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| Euphorbiotheca
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E. deccanensis
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Fruit, member of Euphorbiaceae.[36]
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| Hyphaeneocarpon
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Fruit, member of palm tribe Borasseae.[37]
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| Palmocarpon
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Fruit, member of palm tribe Cocoseae.[38]
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| Palmoxylon
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P. dindoriensis
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Wood, member of palm subfamily Coryphoideae.[39]
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| Pantocarpon
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Fruit, member of Torricelliaceae.[40]
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| Phyllanthocarpon
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P. singpurensis
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Fruit, member of Phyllanthaceae.[41]
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| Rhizopalamoxylon
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Palm rhizome, close affinities to Nypa.[42]
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| Pediastrum
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Algae.[43]
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| Lecaniella
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Algae.[43]
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| Pierceites
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P. deccanensis
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A Dinocyst.[43]
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| Aulacoseira
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A Diatom.[43]
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| Azolla
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Member of Salviniaceae.[43]
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| Crybelosporites
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Member of Marsileaceae.[43]
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| Sparganiaceaepollenites
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Pollen grains, Member of [43]Sparganiaceae/Typhaceae.
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| Marsilea
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Member Marsileaceae.[43]
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| Regnellidium
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Member of Marsileaceae.[43]
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| Nymphaeaceae indet.[43]
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| Typhaceae indet.[43]
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| Liliaceae indet.[43]
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| Acanthaceae indet.[43]
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| Pontederiaceae indet.[43]
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| Ovoidites
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Member of Zygnemataceae.[43]
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| Gabonisporis
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Pollen grains, member of Marsileaceae.[43]
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