Opal Cliffs 1 (Miocene to of the United States)

Also known as UCMP V6875

Where: Santa Cruz County, California (37.0° N, 122.0° W: paleocoordinates 36.7° N, 120.4° W)

• coordinate estimated from map

• outcrop-level geographic resolution

When: Purisima Formation, Messinian to Messinian (7.2 - 3.6 Ma)

• latest Miocene to early Pliocene, somewhat younger than 6.7 +- 0.5 million years old, but not much younger than that date

•Powell et al. [130] chemically correlated an ash bed from the basal portion of the Purisima formation below the Crab Marker Bed with similar deposits elsewhere in California, which have been dated to between 5.6–5.0 and 4.7 Ma. However, this estimate is contradicted by the occurrence of the diatom Thalassiosira miocenica, as well as the apparent absence of T. oestrupii, in the Opal Cliff section, implying its assignment to the upper part of subzone b of the Nitzschia reinholdii zone (6.4-5.5 Ma) [128, 130]. Given the absence of direct dating evidence for the ash layer in the basal Purisima Formation, w here assume a lower age boundary of 6.4 Ma for H. bramblei. This is further supported by the occurrence of UCMP 219079 in a similarly aged horizon (based on diatom data) near the bottom of the San Gregorio section north of Santa Cruz [5]. Magnetostratigraphic correlations recognise a depositional hiatus above the Opal Cliff section, lasting from 4.9–3.7 Ma [128, 130]. Taken together, these observations imply an age range of 6.4–4.9 Ma. (Marx & Fordyce, 2015)

• formation-level stratigraphic resolution

Environment/lithology: open shallow subtidal; sandstone

• strong influence of physical processes (waves, etc.)

Size class: macrofossils

Reposited in the UCMP

Primary reference: F. C. Whitmore and L. G. Barnes. 2008. The Herpetocetinae, a new subfamily of extinct baleen whales (Mammalia, Cetacea, Cetotheriidae). Virginia Museum of Natural History Special Publication 14:141-180 [M. Uhen/M. Uhen/M. Uhen]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 77499: authorized by Mark Uhen, entered by Mark Uhen on 14.01.2008

Creative Commons license: CC BY (attribution)

Taxonomic list

Mammalia
 Cetacea - Phocoenidae
Semirostrum sp.3 Racicot et al. 2014 porpoise
 Cetacea - Balaenopteridae
Balaenopteridae indet.2 Gray 1864 rorqual
 Cetacea - Cetotheriidae
Herpetocetus bramblei n. sp. Whitmore and Barnes 2008 whale
 Carnivora - Odobenidae
Odobenini indet.1 Allen 1880 walrus
UCMP 19004