Loc. 9995 [Agueguexquite Fm] (Pliocene of Mexico)

Where: Mexico (17.6° N, 95.1° W: paleocoordinates 17.7° N, 94.5° W)

• coordinate stated in text

• outcrop-level geographic resolution

When: Agueguexquite Formation, Late/Upper Pliocene (3.6 - 2.6 Ma)

• STRATIGRAPHIC RELATIONS: From the Agueguexquite Formation, for which lithostratigraphic relationships are not stated in english. Overlies the Upper Conception and Filisola Fms (Early-Late Pliocene) according to Collins and Coates (1999, p. 75), and is equivalent to the Tirabuzon Fm of Mexico's Maria Madre Island, and Esmeraldas of NW Ecuador. AGE: Stated to be Middle Miocene. Assigned here, provisionally, to a Pliocene age (see following, from PBDB# 59420: The geological age according to Perilliat (1960) is upper Lower Miocene or lower Middle Miocene (Helvetian or Tortonian). The fauna is apparently closely connected with that from the Choctawhatchee Fm in Florida....The Agueguexquite Fm represents the youngest Miocene deposition as yet found in the Coatzacoalcos Basin and can approximately can be correlated with the Mid-upper Gatun Fm in Panama or with basal Bowden Fm of Jamaica (Thalmann 1935). More recent descriptions of fauna from the Agueguexquite Fm assign it to the Pliocene, more specifically the middle Pliocene (N20). This also matches revised ages for the Bowden Fm, although the Gatun spans the Late Miocene and Early Pliocene. Late Pliocene according to Collins and Coates (1999, p. 75). STRATIGRAPHIC POSITION: From unknown position in formation.

• bed-level stratigraphic resolution

Environment/lithology: coastal; unlithified, micaceous, shelly/skeletal, gray, blue, sandy, carbonaceous claystone

• SEQUENCE STRATIGRAPHY: Accumulated during a marine transgression as evidence by basal pebble lag. ENVIRONMENT: Deposited in shallow warm water within the neritic zone.
• SPECIFIC LITHOLOGY: The sediments consist principally of bluish grey sandy clays, mostly micaceous, with intercalations of grit and sand, poorly bedded, containing a rich fauna of gastropoda and lamellibrancha, and scatterd plant remains. The very base of the unit has layers of quartz pebbles, from hazelnut to walnut in size. LITHIFICATION: No lithification data is reported, however all figured specimens show no evidence of lithified matrix and therefore this collection is assigned as unlithified.

Size class: macrofossils

Collected by Wade in 1920; reposited in the USNM

Collection methods: surface (in situ),

• COLLECTOR: B. Wade (John Hopkins University), 1920. REPOSITORY: IGM, Mexico, and USNM.

Primary reference: M. C. Perrilliat. 1972. Monografia de los Moluscos del Mioceno Medio de Santa Rosa, Verazruz, Mexico. Paleontologia Mexicana 32:1-130 [A. Hendy/A. Hendy]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 77713: authorized by Austin Hendy, entered by Austin Hendy on 17.01.2008

Creative Commons license: CC BY (attribution)

Taxonomic list

• COVERAGE: Exhaustive for gastropoda. NOMENCLATURE: Authoritative publication, with fairly modern nomenclature, and consistent use of subgenera and species-level assignments.
Gastropoda
 Lepetellida - Fissurellidae
Fissurella (Fissurella) mexicana Perrilliat 1972 snail
 Cerithioidea - Turritellidae
Turritella subgrundifera Dall 1892 turret shell
 Sorbeoconcha - Rissoidae
Rissoa epulata Pilsbry and Johnson 1917 snail
Crepitacella cepula Guppy 1866 snail
 Sorbeoconcha - Caecidae
Caecum anellifer Pilsbry and Johnson 1917 snail
Caecum mexicanum Collins 1937 snail
Caecum veracruzanum Collins 1937 snail
Meioceras constrictum Gabb 1873 snail
 Sorbeoconcha - Vitrinellidae
 Heterostropha - Architectonicidae
"Architectonica (Architectonica) nobilis" = Architectonica nobilis
"Architectonica (Architectonica) nobilis" = Architectonica nobilis Röding 1798 sundial
 Neritoidea - Neritidae
Smaragdia (Smaragdia) viridis Linnaeus 1758 snail
SUBSPECIES: Smaragdia (Smaragdia) viridis viridemaris