USGS MR 5066, Alexander Avenue, Marin Headlands (M-2bR) (Cretaceous to of the United States)

Where: Marin County, California (37.8° N, 122.5° W: paleocoordinates 37.0° N, 72.5° W)

• coordinate estimated from map

• outcrop-level geographic resolution

When: Aptian to Aptian (125.0 - 109.0 Ma)

• Assemblage MH-6: Its range is herein considered to be Hauterivian(?) to Albian(?) although correlation with DSDP material (Schaaf,1981) suggests a more restricted late Barremian or Aptian range from the Crolanium pythia zone. Aptian to Early Albian in Kohnen & Murchey, 1995.

• bed-level stratigraphic resolution

Environment/lithology: basinal (siliceous); lithified chert

Size class: macrofossils

Reposited in the USGS

Primary reference: B. Murchey. 1984. Biostratigraphy and lithostratigraphy of chert in the Franciscan complex, Marin Headlands, California. Franciscan Geology of Northern California Field Trip Guidebook 43, Society of Economic Paleontologists and Mineralogists, Pacific Section 51-70 [M. Clapham/M. Clapham]more details

Purpose of describing collection: biostratigraphic analysis

PaleoDB collection 185263: authorized by Matthew Clapham, entered by Matthew Clapham on 17.04.2017

Creative Commons license: CC BY (attribution)

Taxonomic list

Radiolaria
 Nassellaria - Archaeodictyomitridae
Zifondium sp. Pessagno 1977 radiolarian
Thanarla veneta Squinabol 1903 radiolarian
 Nassellaria - Pseudodictyomitridae
Pseudodictyomitra "sp. A" Pessagno 1977 radiolarian