The Lower Cretaceous (Albian) ammonite genera Leconteites and Brewericeras

Cretaceous ammonites from the lower part of the Matanuska Formation, southern Alaska

“…The specimens of B. hulenense from the Matanuska Formation agree well with typical California specimens and also with those from Chitina Valley figured by Imlay (1960) and Jones, Murphy, and Packard (1965). This species is variable in strength of ribbing, width of umbilicus, and ratio of breadth to width, but the few examples dealt with here are insufficient to establish the range of variation.…”

“…This trough extended from the Chitina Valley on the east to beyond the tip of the Alaska Peninsula on the southwest. The formation, which crops out in the Matanuska Valley, the Nelchina area, and the southwest Copper River Lowland, comprises several overlapping prisms of clastic sedimentary rocks which are separated by unconformities (Grantz, 1960a, b;1961a, b;1965). These unconformities record important episodes of uplift and erosion, and thus the prisms they bound are lithogenetic units.…”

Provenance analysis of the Ochoco basin, central Oregon: A window into the Late Cretaceous paleogeography of the northern U.S. Cordillera

“…Mudstone units of the Hudspeth Formation are typically dark gray to black and appear lithologically similar throughout the Mitchell inlier (Wilkinson and Oles, 1968;Jarman, 1973;Kleinhans et al, 1984;Dorsey and Lenegan, 2007). Ammonites found in calcite-cemented concretions in the Main Mudstone member (Kh1) of the Hudspeth Formation are Albian age (McKnight, 1964;Jones et al, 1965;Kleinhans et al, 1984; P. Rodda, personal commun. reported in Dorsey and Lenegan, 2007).…”

“…Our detailed provenance data are consistent with a single Ochoco basin, and our detrital-zircon age data suggest deposition occurred largely during Late Cretaceous time, from Albian through at least Santonian time (ca. 113-86 Ma and younger), rather than deposition (Jones et al, 1965;Wilkinson and Oles, 1968;Kleinhans et al, 1984). Provenance characteristics of the Ochoco basin are consistent with northern sources in the U.S. and southern Canadian Cordillera, and Ochoco strata may represent the destination of much of the "missing" Idaho arc (cf.…”

An Early Albian Arctic-type ammonite Arcthoplites from Hokkaido, northern Japan, and its paleobiogeographic and paleoclimatological implications

“…Since records of Arcthoplites are mainly restricted to the Arctic-Boreal regions, this genus represents an element of the typical Early Albian fauna. In the high latitudes of the North Pacific, species of Arcthoplites have been found in the Lower Albian Brewericeras hulenense Zone of southern Alaska and British Columbia (Jones et al, 1965;Jones and Grantz, 1967;McLearn, 1972), and in the Lower Albian Arcthoplites talkeetnanus Zone of the Korjak-Kamchatka region (Alabushev, 1995) (Fig. 3B).…”