Where: Sonora, Mexico (30.4° N, 112.0° W: paleocoordinates 14.8° S, 108.8° W)

• outcrop-level geographic resolution

When: La Cienega Formation, Nemakit-Daldynian (538.8 - 525.5 Ma)

• 179-m-thick carbonate and clastic marine unit which occurs immediately below the basal volcaniclastic conglomerates and siltstones of unit 1 of hte Lower Cambrian Puerto Blanco Formation. Fossils are approximately 130m below the base of the Puerto Blanco Formation and form discontinuous tabular and lenticular deposits a few centimeters to over a meter in thickness

• bed-level stratigraphic resolution

Environment/lithology: marine; lithified, dolomitic, ooidal, shelly/skeletal, sandy limestone

Size classes: mesofossils, microfossils

Preservation: trace, recrystallized, original calcite, original phosphate, replaced with silica

Collection methods: bulk, chemical,

• It should be noted that no fossils have been found in the La Cienega Formation which are known to be restricted to the Meishucunian or Tommotian Stage. Specimens were removed from carbonate using 10% solution of acetic acid then recovered using a 150 micrometer sieve.

Primary reference: M. A. S. McMenamin. 1985. Basal Cambrian small shelly fossils from the La Ciengega Formation, northwestern Sonora, Mexico. Journal of Paleontology 59(6):1414-1425 [M. Patzkowsky/P. Borkow]more details

Purpose of describing collection: biostratigraphic analysis

PaleoDB collection 10578: authorized by Mark Patzkowsky, entered by Phil Borkow on 25.05.2001

Creative Commons license: CC BY (attribution)