Bed 28, Section 1 - Lajas (Yumagual Fm): Cenomanian, Peru
List of taxa
Where & when
Geology
Taphonomy & methods
Metadata & references
Taxonomic list
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Bivalvia
- Ostreida
- Arctostreidae
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Exogyra mermeti
Coquand 1882
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| synonym of Rhynchostreon mermeti | |||||||
| see common names | |||||||
Geography
| Country: | Peru | State/province: | Cajamarca |
| Coordinates: | 6.6° South, 78.7° West (view map) | ||
| Paleocoordinates: | 13.3° South, 54.2° West | ||
| Basis of coordinate: | based on nearby landmark | ||
| Geographic resolution: | outcrop |
Time
| Period: | Cretaceous | Epoch: | Late/Upper Cretaceous |
| Stage: | Cenomanian | 10 m.y. bin: | Cretaceous 5 |
| Key time interval: | Cenomanian | ||
| Age range of interval: | 100.50000 - 93.90000 m.y. ago |
Stratigraphy
| Geological group: | Pulluicana | Formation: | Yumagual | ||
| Local section: | Lajas | Local bed: | 865 m | ||
| Local order: | top to bottom | ||||
| Stratigraphic resolution: | group of beds | ||||
| Stratigraphy comments: Collection from a 159 m thick marl unit, lying immediatelyy below the Choro Member of the Mujarrun Formation (early Cenomanian) and above the Pariatambo Formation (middle Albian). The member is as much as 760 m thick in the region. The formation contains two biozones, a lower zone with late Albian index taxa, and an upper zone with early Cenomanian fauna. | |||||
Lithology and environment
| Primary lithology: | concretionary,shelly/skeletal poorly lithified carbonaceous marl |
| Secondary lithology: | wave ripples,gray argillaceous "limestone" |
| Includes fossils? | Y |
| Lithology description: Marl, somewhat bituminous, soft, nodular, richly fossiliferous, interbedded with a few beds of massive, wavy bedded, light gray, argillaceous limestone. | |
| Environment: | carbonate indet. |
| Glacial or sequence phase: | regressive |
| Geology comments: Accumulated during a shallowing of regional seas, with accumulation of shallow-water marls and limesyones, with occasional interfingering quartz-siltstones, with abundant benthic lifer, but scare ammonites. | |
Taphonomy
| Modes of preservation: | body |
| Size of fossils: | macrofossils |
Collection methods and comments
| Collection methods: | selective quarrying,field collection |
| Reason for describing collection: | general faunal/floral analysis |
| Museum repositories: | AMNH |
| Collection method comments: Collections reposited at AMNH. | |
| Taxonomic list comments:Taxonomic list compiled by the author during 1951-1952. Nomenclature should therefore be somewhat antiquated, though systematics reflect supervision of Normal Newell, Columbia University and AMNH paleontologists. | |
Metadata
| Database number: | 56905 | ||
| Authorizer: | A. Hendy | Enterer: | A. Hendy |
| Modifier: | A. Hendy | Research group: | marine invertebrate |
| Created: | 2005-11-28 21:55:13 | Last modified: | 2013-11-25 13:37:23 |
| Access level: | the public | Released: | 2005-11-28 21:55:13 |
| Creative Commons license: | CC BY |
Reference information
Primary reference:
| 15338. | V.E. Benavides-Caceres. 1956. Cretaceous system in northern Peru. Bulletin of the American Museum of Natural History 108(4):1-493 [A. Miller/A. Hendy] |