Benthonic Foraminiferal Assemblages Research Articles

Foraminiferal and Nannoplankton Biostratigraphy, Paleoecology, and Basinal Reconstruction, Anita Formation, Western Santa Ynez Mountains, California: ABSTRACT

The Anita Formation crops out along the crest of the Santa Ynez Mountains, California, from Santa Ynez Peak westward to Point Conception. Planktonic and benthonic foraminiferal faunas and calcareous nannoplankton floras were studied from 6 measured sections between Arroyo el Bulito and Santa Ynez Peak. In general, Anita Formation strata are assigned to the time interval from early Paleocene to early middle Eocene on the basis of prevailing planktonic correlations. Also from planktonic evidence, reported Ynezian benthonic foraminiferal assemblages appear to be early Paleocene to late Paleocene in age; Bulitian assemblages are of late Paleocene age; Penutian assemblages are late Paleocene in some sections and early Eocene in others; Ulatisian assemblages are late Paleocene o early middle Eocene. The time-transgressive nature of the benthonic provincial stages is apparent; the stages become geologically younger toward the basin margins as well as stratigraphically higher. Furthermore, strata mapped as Anita Formation by Dibblee have been found to be of late Cretaceous age in several areas. Lithologically, the Anita Formation can be split into three gross members, which can be mapped throughout the Western Santa Ynez Range. The unit is divisible into the following stratigraphic units, all of which are typed in the upper Arroyo el Bulito area: Gato siltstone (upper member); Augustin mudstone (middle member); and Bulito siltstone (lower member). The Anita Formation is thickest south of the present Santa Ynez fault system, whereas northward, telescoped sections occur, and the Anita gradually disappears. This relation suggests that the Santa Ynez fault may have been a prominent structural feature in early Paleogene time. Eastward the Anita wedges into Matilija type clastics, which were shed from the nearby San Marcos high. Southward the Anita disappears under the Santa Barbara Channel. End_of_Article - Last_Page 781------------

Foraminifera from the Cretaceous Neogastroplites Zone Moberly Lake, British Columbia

ABSTRACT Thirty-seven species belonging to sixteen genera of arenaceous foraminifers and one species of radiolarian (Dictyomitra) are recovered from the mid-Cretaceous lower part of the Neogastroplites Zone of the Fort St. John Group of the Moberly Lake area of northeastern British Columbia, Canada. The benthonic foraminiferal assemblage contains Bathysiphon, Saccammina, Ammodiscus, Glomospira, Trochamminoides, Reophax, Miliammina, Psamminopelta, Haplophragmoides, Ammobaculites, Textularia, Trochammina, Verneuilina, Verneuilinoides, Tritaxia and Gaudryina. Correlative elements indicate a relationship with the boreal faunas of the Grandstand and Topagoruk formations of the Alaskan coast and with forms from the Graneros and Mowry formations of the western interior of the United States. The accompanying ammonites Neogastroplites haasi and N. cornutus are indicative of late Albian age for the strata sampled. The sediments were deposited in the shallow, slightly freshened margins of the euxinic Mowry sea near the base of the upper, aerated layer, close to the northeastern pinchout margin of the Goodrich Sandstone Formation.

Foraminiferal evidence for a pre‐middle eocene age of the chatham rise, New Zealand

Summary Several sediment samples collected from the crest and slope of the Chatham Rise, and from the Chatham Islands, to the east of New Zealand, contain Globigerina linaperta‐Globorotalia increbescens foraminiferal faunas of upper Middle and middle Upper Eocene age. The foraminiferal faunas from the Chatham Islands, which include Rectuvigerina, Latibolivina, Dyocibicides, Discorbinella, Patellina, and Wadella, indicate shallow‐water palaeodepths, probably equivalent to the outer shelf (50–150 m). A faunal assemblage from near the crest of the rise is likewise indicative of shallow water, although distinct differences in the benthonic foraminiferal ifauna suggest slightly deeper‐water biofacies than the Eocene of the Chatham Islands. In contrast, a fauna of similar age from 1,100 m on the southern slope of the Chatham Rise contains a much deeper‐water benthonic foraminiferal assemblage including Osangularia, Vulvulina, Stilostomella, hispidocostate Uvigerina, and smooth‐shelled Bulimina, indicative of lo...