Boron (Miocene of the United States)

Also known as UCR RV-6421; United States Borax and Chemical Corporation mine

Where: San Bernardino County, California (35.1° N, 117.7° W: paleocoordinates 36.0° N, 114.2° W)

• coordinate based on political unit

• small collection-level geographic resolution

When: Arkose Member (Kramer Beds Formation), Early/Lower Hemingfordian (20.4 - 16.0 Ma)

Environment/lithology: fluvial; micaceous, volcaniclastic, brown claystone and silty sandstone

• "Observations made in the pit in 1964 and from the fossil-bearing matrix indicate the fossils were restricted to one or more beds of light tan micaceous clay- stones which locally contain pumice lapilli fragments. These beds were part ofa sequence offluviatile siltstones and sand- stones locally cut by channels of coarser arkosic sandstones and pebble conglomerates. About 3 m above the fossil-pro- ducing beds were several discontinuous lenses of grayish- pink bentonitic tuff and yellowish-white, medium-grained sandy tuff."

Size classes: macrofossils, mesofossils

Collected in 1964

• "Fossils of the Boron Local Fauna were not observed at the original site of deposition by the author. They were first noticed by several mine employees operating heavy equip- ment removing overburden from the open pit mine. The mine foreman informed the geology staff who had the remaining fossil-bearing matrix dumped in a separate location from the general mine dump so that the fossils could be recovered. It is not certain how much of the fossil-bearing pocket was lost before this action was taken, but 4-5 earth-mover loads (12-15 cubic meters) were subsequently recovered before the pocket stopped producing readily visible fossil bone."

Primary reference: D. P. Whistler. 1984. Boron Local Fauna. Contributions in Science, Natural History Museum of Los Angeles County 355:1-36 [J. Alroy/J. Alroy/M. Uhen]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 19194: authorized by John Alroy, entered by John Alroy on 18.02.1993

Creative Commons license: CC BY (attribution)

Taxonomic list

• 146 m over basalt dated at 18.3 +/- 0.6, 19.7 +/- 0.6, 20.3 +/- 0.7 Ma; last date is definitely KA
NISP 115
Mammalia
 Rodentia - Sciuridae
? Miospermophilus sp. Black 1963 squirrel
 Rodentia - Heteromyidae
Cupidinimus boronensis n. sp. Whistler 1984 rodent
Perognathinae indet. Coues 1875 rodent
Trogomys cf. rupinimenthae Reeder 1960 rodent
 Lagomorpha - Leporidae
Archaeolaginae indet. rabbit
"Archaeolagus sp. or Hypolagus sp."
 Ungulata - Merycoidodontidae
? Merychyus sp. Leidy 1858 oreodont
Merychyus cf. minimus Peterson 1907 oreodont
 Ungulata - Camelidae
Camelidae indet. Gray 1821 camel
two forms
cf. Hesperocamelus sp. Macdonald 1949 camel
repeated by Honey et al. 1998;
 Ungulata - Palaeomerycidae
Aletomeryx occidentalis n. sp. Whistler 1984 ruminant