W. R. Riedel

Radiolarians, diatoms, silicoflagellates and calcareous nannofossils in the Mediterranean Neogene

Radiolarian fauna described (one new genus, four new species), diatom, silicoflagellate and nannofossil assemblages related to radiolarians, zonations correlated, Miocene, Pliocene, Majorca, Italy

The El Cuervo section (Andalusia, Spain): Micropaleontologic anatomy of an early Late Miocene lower bathyal deposit

Abstract An examination of its calcareous and siliceous microfauna and microflora indicates that the El Cuervo section (Andalusia, Spain) is a lower bathyal deposit (formed between 1000 and 1500 m in a zone of near-coastal upwelling) of early Late Miocene age, penecontemporaneous with the lower part of the stratotype Andalusian Stage and equivalent to, at least, a part of Magnetic Epochs 10 and/or 11. The bottom depths where the benthonic fauna (foraminifera and ostracodes) lived at the time of deposition were well beneath the boundary between the upper warm mixing zone (thermosphere) of the Atlantic and Tethys and the lower permanently cold layers (psychrosphere) originating only in the Atlantic. Mixing of the deep faunas of Tethys and the Atlantic is indicated. The El Cuervo fauna is part of an important sequence of sections in which the benthonic fauna indicates a deep passage (Iberian Portal) from the Atlantic into Tethys in southern Spain. The significance of this section on the Late Miocene closure of the Iberian Portal is discussed.

Advances in ichthyolith stratigraphy of the Pacific Neogene and Oligocene

To improve the resolution of ichthyolith stratigraphy in the Pacific Neogene and Oligocene, 12 new taxa are described, and their ranges are determined in Giant Piston Core 3 and in 104 samples dated by means of calcareous microfossils. These new ichthyoliths increase by one-third the number of reliable ichthyolith stratigraphic events for the sequences studied. The stratigraphic utilization of these microfossils is improved by adaptation of a scheme which assesses the relative reliability of earliest and latest occurrence data in correlated sequences. This procedure allows for less subjective decisions regarding the stratigraphic dependability of individual forms and provides a basis for choosing between conflicting correlation lines.

Stratigraphic Interpretations of Pelagic Sequences Revised on the Basis of Ichthyoliths

Ichthyoliths are applied for stratigraphic interpretation of unfossiliferous and unreliably dated parts of sediment sequences obtained from Deep Sea Drilling Project Sites 250, 256, 257, 259, 287, 290, 367, 382 and 385. Preliminary to these interpretations, a firmer basis is established for correlation of ichthyolith ranges with Tertiary calcareous nannofossil zones. Based on new evidence, ichthyolith assemblages change significantly at or near the Maestrichtian/Paleocene boundary, not within the Paleocene as previously interpreted. This permits the placement of this boundary in the SE Indian Ocean DSDP Site 256 and North Atlantic Site 367. At SW Indian Ocean Site 250, Eocene/Oligocene sediments are estimated to have accumulated at 2-3 m/Ma, whereas the overlying Miocene and Pliocene sediments accumulated at 25 m/Ma. At western North Pacific Site 290, the rate of accumulation of post-Oligocene sediments is approximately 1.5 m/Ma rather than the 2.2 m/Ma estimated by the original investigators. Ichthyoliths indicate that Early and Middle Miocene strata at SW Pacific Site 287 are missing or greatly compressed. A pronounced disconformity, representing the Late Paleocene and the entire Eocene, is recognized at Site 382 in the New England Seamount Chain. Stratigraphic interpretations of pelagic sequences revised on the basis of ichthyoliths

Quantitative description of pore patterns in radiolarians

The arrangement of pores in the lattice-shells of radiolarians can be an important descriptor of the skeletons, if the pattern can be characterized quantitatively. An image analysis system integrated with a personal computer provides a convenient means of measuring distances between pores, and their angular relations, together with the variability of those measures. Both regular and irregular patterns can be quantified. The procedure is adaptable to a wide spectrum of patterns in the organic world. f-~ /~~~~~~~~~~~~~~~~~~~

RADIOLARIA FROM THE FRANCISCAN GROUP, BELMONT, CALIFORNIA

Radiolaria recently found in shale of the Franciscan group (Jurassic and Cretaceous) in California are somewhat better preserved than those previously found in cherts of this group. Seven forms are described, figured, and identified generically. Radiolaria from the Franciscan group, Belmont, California WILLIAM R. RIEDEL AND JULIUS SCHLOCKER Scripps Institution of Oceanography, La Jolla, California, and U. S. Geological Survey, Menlo Park, California