Tomah Mbr, Franconia Fm - Bed 9, Lake City section (Cambrian of the United States)

Where: Wabasha County, Minnesota (44.4° N, 92.3° W: paleocoordinates 19.7° S, 80.1° W)

• coordinate based on nearby landmark

• outcrop-level geographic resolution

When: Tomah Member (Franconia Formation), Franconian (497.0 - 485.4 Ma)

• LITHOSTRATIGRAPHY: Tomah Mbr of the Franconia Fm (following Ber 1953, 1954). STRATIGRAPHIC RELATIONS: From the Tomah Mbr, the middle member of the Franconia Fm, which is overlain by the Reno Mbr. The Franconia Fm is overlain by the Black Earth Mbr of the St Lawrence Fm. AGE: From near the top of the Ptychaspis granulosa zonule, Ptychaspis-Prosaukia Zone (Howell et al. 1944) of the Middle Croixan. STRATIGRAPHIC POSITION: Unit 9, .5 ft thick, in the lower portion of a 65+ ft thick section.

• bed-level stratigraphic resolution

Environment/lithology: offshore; lithified, fine-grained, micaceous sandstone

• ENVIRONMENT: From text: "...shallow marine water on a slightly irregular shelf...deposition in quiet water, protected from more aggitated environments", assigned to a siliciclastic - offshore environment. TECTONIC SETTING: Tectonic data not reported in text. SEQUENCE STRATIGRAPHY: Sequence stratigraphic data not reported.
• GENERAL LITHOLOGY: Fine-grained, micaceous sandstone and siltstone, cemented by authigenic feldspar, with shale laminae on many of the bedding surfaces. LITHIFICATION: Assumed to be lithified, based on age and observation of figured specimens.

Size class: macrofossils

Preservation: cast, mold/impression

Reposited in the USNM

Collection methods: bulk, quarrying,

• COLLECTOR: R.E Grant. REPOSITORY: USNM

Primary reference: R. E. Grant. 1962. Trilobite distribution, upper Franconia Formation (Upper Cambrian), southeastern Minnestoa. Journal of Paleontology 36(5):965-998 [A. Miller/A. Hendy]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 62106: authorized by Austin Hendy, entered by Austin Hendy on 12.07.2006

Creative Commons license: CC BY (attribution)

Taxonomic list

• COMPLETENESS: Limited to trilobita, exhaustive for trilobites, however. NOMENCLATURE: Authoritative publication, but somewhat historic nomenclature.
Show authors, comments, and common names
Trilobita
 Olenida - Idahoiidae
Idahoia serapio
Idahoia serapio Walcott 1924 trilobite
 Asaphida - Ptychaspididae
Ptychaspis granulosa
Ptychaspis granulosa Owen 1852 trilobite