UCMP 7004, Simi Valley (Eocene of the United States)

Where: Ventura County, California (34.3° N, 118.7° W: paleocoordinates 35.1° N, 104.6° W)

• coordinate estimated from map

• outcrop-level geographic resolution

When: Llajas Formation, Lutetian (47.8 - 41.3 Ma)

• From the "Domengine" horizon of the Eocene of Simi Valley.

• group of beds-level stratigraphic resolution

Environment/lithology: transition zone or lower shoreface; lithified, fine-grained, brown, yellow sandstone

• The "Stewart bed" is located in a section of transition from shallow-marine to outer slope and shelf facies. A nearshore environment is interpreted for that portion of the shallow-marine (transgressive) facies which consists of laminated beds alternating with bioturbated beds. In such cases, the finely laminated sand represents storm-influenced stratification, and the biogenic reworking is the inter-storm activity. Shell fragments commonly are concentrated as channel lags in surge channels. Fossils were apparently subjected to wave action because the apices of elongate shells such as Turritella are bimodally oriented in opposite directions. The deeper the water, the less amount of laminated sandstone and the more amount of bioturbated sandstone. Such areas, which were farther below effective wave base, existed 1) where the shallow-marine (transgressive) facies grades into the outer shelf to slope facies and 2) in the shallow-marine (regressive) facies. One of the deepest-water shallow-marine beds was the "Stewart bed."

Size class: macrofossils

Collected by R. B. Stewart; reposited in the UCMP

Primary reference: H. G. Schenck. 1931. Cephalopods of the genus Aturia from western North America. University of California Publications, Bulletin of the Department of Geological Sciences 19:435-490 [M. Clapham/K. Okamoto/M. Clapham]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 166460: authorized by Matthew Clapham, entered by Kristina Okamoto on 14.02.2015, edited by Jonathan Marcot and Patricia Holroyd

Creative Commons license: CC BY (attribution)

Taxonomic list

Bivalvia
 Ostreida - Malleidae
Exputens llajasensis n. sp.1 Clark 1934 oyster
Gastropoda
 Tonnoidea - Cassidae
"Galeodea (Caliagaleodea) californica n. sp." = Galeodea californica2
"Galeodea (Caliagaleodea) californica n. sp." = Galeodea californica2 Clark 1942 snail
Cephalopoda
 Nautilida - Aturiidae
Aturia myrlae Hanna 1927 nautiloid