SHELIKOF FORMATION

Ages of the Shelikof Formation between Wide Bay and Puale Bay based on ammonites

The ammonites collected in 1980 from the Shelikof Formation on the Alaska Peninsula represent most the same taxa that were collected previously (Imlay, Prof. Paper 836, p. 3, 7, 12, 13) except for the absence of Kepplerites and the presence of Xenocephalites. Among the genera present, Pseudocadoceras in Europe (Prof. Paper 836, fig. 7) ranges from the upper part of the lower Callovian to the top of the Callovian. In southern Alaska Pseudocadoceras occurs in the upper three fourths of the Chinitna Formation in beds that are dated as late early and middle Callovian (See Prof. Paper 836, p. 6, 14). On the Alaska Peninsula Pseudocadoceras ranges from the very top of the lower member of the Shelikof Formation into the basal beds of the upper member and is dated as mainly of middle Callovian age (Prof. Paper 836, p. 12, 14). Stenocadoceras in Europe ranges upward from upper lower Callovian to the lower part of the upper Callovian (Prof. Paper 836, fig. 7 on p. 13). Stenocadoceras in southern Alaska has stratigraphic and age ranges identical with those of Pseudocadoceras. Cadoceras in Europe and in Alaska ranges through beds of early and middle Callovian ages, but the species Cadoceras catostoma Pompeckj in Alaska has been found ony in beds of early Callovian age. Iniskinites and Xenocephalites west of Cook Inlet occur throughout much of the Bowser Formation of Bathonian age. They occur also in the basal beds of the Chinitna and Shelikof Formations which are of earliest Callovian rather than latest Bathonian age based on their associations with Cadoceras (See Prof. Paper 1091, p. 14-16 and PP. 836, p. 6).

In summation, most of the ammonites collected in 1980 from the Shelikof Formation were obtained from the middle member and are of middle Callovian age. Ammonites that are definitely of early Callovian age include Cadoceras catastoma Pompeckj at localities 80ADt216 and 80ADt216A, Xenocephalites at locality 80ADt239, and Iniskinites at locality 80ACe153. Elsewhere in southern Alaska, Cadoceras catostoma has been found only in beds of early Callovian age; Xenocephalites ranges upward through most of the Bathonian sequence (see Prof. Paper 1091, figs. 2 and 5) but occurs also into the basal beds of the Chinitna Formation; and Iniskinites ranges upward through the late middle to late Bathonian sequence into the basal beds of the Chinitna Formation. Neither Xenocephalites or Iniskinites range into the basal part of the range of Cadoceras catostoma (see Prof. Paper 836, p. 12, 14, and Prof. Paper 1091, p. 14).

AMMONITE TAXA IN THE SHELIKOF FORMATION LISTED BY LOCALITIES

Phylloceras bakeri - 80ACe224, 80AAy1.
Phylloceras cf. P. bakeri Imlay - 80ADt 238D
Phylloceras sp. - 80ACe222
Xenocephalites hebetus Imlay - 80ADt239
Lilloettia stantoni Imlay - 80ADt216A
Lilloettia sp. - 80AJm13A
Iniskinites sp. - 80AJm13A
Cadoceras wosnessenskii (Grewingk) - 80ACe185, 185B, 198; 80ADt216
Cadoceras catostoma Pompeckji - 80ACe185, 185B, 198; 80ADt216
Catostoma tenuicostatum Imlay - 80AAy60A, 80ACe198
Cadoceras spp. - 80ACe105, 80AAy60, 80ACx30
Cadoceras? sp. 80ACx19, 80AJm7
Cadoceras (Stenocadoceras) cf. C. (S).) striatum Imlay - 80ACe119, 80AJm8
C. (Stenocadoceras) stiatum Imlay - 80AWs249
C. (Stenocadoceras) multicostatum Imlay - 80ACe147, 151B, 205A, 220, 222, 80AAy1, 60, 60A
C. (Stenocadoceras) cf. C. (S.) multicostatum Imlay - 80ADt204, 211, 275, 245
C. (Stenocadoceras) iniskinense Imlay - 80ADt338C
C. (Stenocadoceras) cf. C. (S). iniskinense Imlay - 80ACe205A
C. (Stenocadoceras) stenoloboide Pompeckj - 80ADt245
C. (Stenocadoceras) cf. C. (Stenocadoceras) stenoloboide Pompeckj - 80ADt238B, Fs 2 on Helen Creek.
Cadoceras (Stenocadoceras) sp. - 80ADt238D, 80AJm1
C. (Stenocadoceras?) sp. - 80ADt274
Pseudocadoceras petelini (Pompeckj) - 80ACe105, 111, 113A; 80ADt181, 202, 203, 291, 265; 80AAy82
Pseudocadoceras cf. P. petelini (Pompeckj) - 80ACe220, 80ADt238A
Pseudocadoceras cf. P. schmidti (Pompeckj) - 80ACe185A
Pseudocadoceras grewingki (Pompeckj) - 80ACe220, 80ADt181, 202, 265, 80AJm7
Pseudocadoceras crassicostatum Imlay - 80AAy82
Pseudocadoceras sp. - 80ADt238B