Where: Beaverhead County, Montana (44.5° N, 112.6° W: paleocoordinates 44.8° N, 71.0° W)
• coordinate based on nearby landmark
• small collection-level geographic resolution
When: Flood Member (Blackleaf Formation), Late/Upper Albian to Late/Upper Albian (105.3 - 93.9 Ma)
• The BL1 locality occurs 102m above the Kootenai– Blackleaf contact, a stratigraphic position within the Flood Member within this outcrop region.
•Fossils are in unit 59.
• bed-level stratigraphic resolution
Environment/lithology: fluvial-deltaic; fine, green, sandy siltstone
• low-energy fluvial–deltaic and estuarine
• 0.6m thick unit consists of a green, sandy siltstone with approximately 5% of its composition represented by fossils. More detailed compositional analysis shows that the fossil-bearing bed contains approximately 7% very fine sand size grey quartz grains, 3% fine sand size grey quartz grains, 4% fine sand size black or orange chert grains and 1% very fine sand size biotite flakes. The remaining 80% (approximately) is represented predominantly by silt with little clay. Very fine and fine sand size quartz grains are subrounded to subangular in form, whereas all fine-size chert grains are well rounded. The fossil-bearing bed is horizontally discontinuous and roughly lenticular. The calcite-cemented unit fines upwards to become increasingly silt dominated with fewer fossils and exhibits a pervasive (stratigraphy parallel) platy weathering texture. The bed also contains a few smooth, reddish coloured, undulating, locally small surfaces. These likely represent postlithification slickensides coloured red by iron concentration and oxidation (Aschoff and Schmitt 2004). Fossils are permineralised with calcite and dark brown in colour. Both teeth and bone range from less than 1 to 20mm in size.
Size classes: macrofossils, mesofossils
Collected in 2005 and 2006
Primary reference: P. V. Ullmann, D. Varricchio, and M. J. Knell. 2012. Taphonomy and taxonomy of a vertebrate microsite in the mid-Cretaceous (Albian–Cenomanian) Blackleaf Formation, southwest Montana. Historical Biology 24(3):311-328 [P. Mannion/P. Mannion]more details
Purpose of describing collection: general faunal/floral analysis
PaleoDB collection 137590: authorized by Philip Mannion, entered by Philip Mannion on 18.12.2012
Creative Commons license: CC BY (attribution)
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