False Pass (M7256) (Miocene of the United States)

Also known as USGS M7256

Where: Aleutians East County, Alaska (54.9° N, 163.0° W: paleocoordinates 55.9° N, 161.4° W)

• coordinate stated in text

• outcrop-level geographic resolution

When: Tachilni Formation, Tortonian (11.6 - 7.2 Ma)

• Formation crops out continuously from the coast west of Cape Tachilni from Morzhovoi Bay to False Pass and possibly of Deer Island. Thickness of the Tachilni Fm is not known because its base is not exposed, but is estimated to be as much as 460 m thick, although not more than 250 m and any outcrop. Disconformably overlies volcaniclastic Belkofski Fm, and is unconformably overlain by Pliocene-Holocene volacanic flows and breccia.

• bed-level stratigraphic resolution

Environment/lithology: coastal; fine-grained, medium, brown, gray sandstone

• Composed mostly of dark brown to light greenish-gray, fine- to coarse-grained sandstone, abundant similarly colored siltstone, with some pebble conglomerate and black shale....mainly a fine- to medium-grained sandstone.

Size class: macrofossils

Reposited in the CAS, USNM

Collection methods: quarrying,

• Also collections at University of Alaska (UA), Fairbanks, Alaska

Primary reference: L. Marincovich. 1983. Molluscan paleontology, paleoecology, and North Pacific correlations of the Miocene Tachilni Formation, Alaska Peninsula, Alaska. Bulletin of American Paleontology 84(317):1-155 [A. Miller/A. Hendy/A. Hendy]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 37409: authorized by Austin Hendy, entered by Austin Hendy on 14.03.2004

Creative Commons license: CC BY (attribution)

Taxonomic list

• Exhaustive for molluscan taxa
Bivalvia
  -
Bivalvia indet. Linnaeus 1758 clam
 Pholadida - Myidae
Mya (Mya) truncata Linnaeus 1758 softshell clam
 Cardiida - Mactridae
"Spisula (Mactromeris) polynyma" = Mactromeris polynyma, Spisula sp.
"Spisula (Mactromeris) polynyma" = Mactromeris polynyma Stimpson 1860 clam
Spisula sp. Gray 1837 clam
 Cardiida - Tellinidae
Macoma sp. Leach 1819 tellin clam
 Cardiida - Cardiidae
"Clinocardium cf. ciliatum" = Clinocardium (Ciliatocardium) ciliatum Fabricius 1780 cockle
Clinocardium sp. Keen 1936 cockle
Clinocardium cf. pristinum Keen 1954 cockle
 Solenida - Pharidae
 Protobranchia - Sareptidae
Gastropoda
  -
Gastropoda indet. Cuvier 1797 snail
 Neogastropoda - Buccinidae
 Neogastropoda - Conidae
 Naticoidea - Naticidae
Naticidae indet. Guilding 1834 moon snail