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Geology topics

David Bukry

Publications and source records attributed to David Bukry.

69 records · Page 4Linked to original sources
USGS1979

Comparison of Miocene provincial foraminiferal stages to coccolith zones in the California Continental Borderland

Biostratigraphic ages determined by planktic coccoliths and benthic foraminifera for the same core samples from the California Continental Borderland suggest that a significant overlap exists among provincial Miocene stages of California and that some of the benthic foraminifera commonly used to recognize these stages are time-transgressive. For example, samples assigned to the middle Miocene Discoaster exilis Zone of coccoliths (∼ 14 ± 1 m.y.) are also assigned to the Relizian, Luisian, and lower Mohnian Stages on the basis of benthic foraminifera. Significantly, most past and current geologic interpretations of Cenozoic marine sequences in California rely heavily on provincial benthic foraminiferal stages and zones. Thus, the apparent overlapping of provincial stages has serious implications for geologic studies of the California Cenozoic and should be further investigated in sections onshore.

California↗
USGS1979

Coccolith and silicoflagellate stratigraphy, northern mid-Atlantic Ridge and Reykjanes Ridge, Deep Sea Drilling Project Leg 49

Leg 49 of the Deep Sea Drilling Project recovered 192 cores at eight drilling sites, 407 through 414 (Figure 1). Light-microscope techniques were used to study the cocoliths, silicoflagellates, and sponge spicules of 120 samples from these cores. The cocolith zonation of the samples follows Bukry (1975a), and is summarized in Figure 2. Silicoflagellate zonation, summarized in Figure 3, is explained in the text. Siliceous sponge spicules are common in many samples and are briefly discussed and illustrated. One new silicoflagellate, Distephanus sulcatus , from the Plicene of Site 407, is described.

Initial reports of the Deep Sea Drilling Project↗
USGS1977

Descriptions of pre-Quaternary samples, R/V Ellen B. Scripps, September 1976, Patton Ridge to Blake Knolls, California continental borderland

A sampling cruise under the joint sponsorship of Scripps Institution of Oceanography and the U. S. Geological Survey was completed in early October 1976 as part of the Survey's resource and environmental studies on the California Continental Borderland. J. K. Crouch was Chief Scientist for the cruise aboard R/V ELLEN B. SCRIPPS. Samples were taken entirely by means of dart corers, and navigation for sample sites was done using the LORAC system supported by shipboard radar. Depths were corrected for sound-velocity variations in water (Matthews, 1939). In some instances, recorded depths in the table may not match bathymetric contours on published maps because of imprecise navigation on pre-1940 surveys.

California↗
USGS1975

Morphology and phylogeny of the coccolithophycean family Ceratolithaceae

The family Ceratolithaceae includes a group of horseshoe-shaped calcareous nannofossils and contains ten species which are assignable to two genera: Amaurolithus n. gen. and Ceratolithus . Species of Amaurolithus are characterized by showing faint or no birefringence in cross-polarized light when viewed in preferred orientation. Included in Amaurolithus are A. amplificus (Bukry and Percival), A. Mzzarus (Bukry), A. delicatus n. sp., A. primus (Bukry and Percival), and A. tricorniculatus (Gartner). Species of Ceratolithus are characterized by their strong birefringence in cross-polarized light when viewed in preferred orientation. Ceratolithus includes C. acutus Gartner and Bukry, C. armatus Miiller, C. cristatus Kamptner, C. rugosus Bukry and Bramlette, and C. telesmus Norris. The family first appears in the geologic record during the late Miocene, represented by the nonbirefringent-appearing species that constitute the genus Amaurolithus . A succession of these species persists into the early Pliocene. The distinctly birefringent forms assigned to the genus Ceratolithus first appear near the base of the Pliocene; the succession has persisted to modern time.

Journal of Research of the U.S. Geological Survey↗
USGS1974

Stratigraphic value of silicoflagellates in nontropical regions

Silicoflagellates are important biostratigraphic markers for age determination in nontropical regions because age-diagnostic calcareous microfossils are sparse. Upper Cretaceous and Cenozoic biostratigraphic zonation is proposed, based on silicoflagellates from Deep Sea Drilling Project sites in the subantarctic region.

GSA Bulletin↗
USGS1974

Silicoflagellate zonation of upper Cretaceous to lower Miocene deep-sea sediment

A stratigraphic zonation based on silicoflagellates is proposed for the division of Upper Cretaceous to lower Miocene deep-sea sediments into eight independent zones. The occurrence of silicoflagellate siliceous microfossils from Mesozoic and lower Cenozoic sediment has been poorly known in all but the middle Eocene. The most diagnostic occurrences in deep-sea sediment are here used to define a sequence of zones, which are correlated with the more widely recognizable zonation of coccoliths. The silicoflagellate zones defined include the Lyramula furcula Zone of Late Cretaceous age, the Corbisema hastata Zone of Paleocene age, the Naviculopsis constricta Zone and Dictyocha hexacantha Zone of Eocene age, the Dictyocha deflandrei Zone and Rocella gemma Zone of Oligocene age, and the Naviculopsis quadrata Zone and Distephanus octacanthus Zone of early Miocene age.

Journal of Research of the U.S. Geological Survey↗
USGS1973

Basement ages and basement depths in the eastern equatorial pacific from Deep Sea Drilling Project Legs 5, 8, 9, and 16

Recent literature contains numerous references to basement ages and basement depths determined by the Deep Sea Drilling Project. The data are derived from a variety of sources, many of them inadequately documented or preliminary, and are not uncommonly inaccurate or conflicting. In this paper we present tabulations of basement ages and depths from DSDP Legs 5, 8, 9, and 16 in the eastern equatorial Pacific, refer them to the latest biostratigraphic time scale, and document and discuss their error limits. We recommend that in future use of this type of data a similar practice be adopted and that the precise source of data, time scale used, and procedures for determining ages and errors be clearly identified in order to avoid confusion. Based on the data presented here, we also give the relations between basement age, distance from the spreading center, and basement depth. The errors inherent in the data cause these relations to be very general and to have less resolution than ascribed to them by some previous investigators.

GSA Bulletin↗
USGS1970

Geological significance of coccoliths in fine-grained carbonate bands of postglacial Black Sea sediments

The origin of fine carbonate muds in deep parts of the Black Sea has been explained in various ways, but details of how the carbonate was formed are poorly understood. We have studied samples containing fine carbonate from cores obtained during the cruise of Atlantis II (Woods Hole Oceanographic Institute) to the Black Sea in April and May 1969. Examination of the light-coloured bands and darker bands by scanning electron micrographs and light microscopy shows that Holocene coccoliths are the overwhelmingly dominant constituents in the light bands, whereas Cretaceous and Eocene coccoliths are important components of the carbonate in the darker matrix.

Nature↗