Orville L. Bandy

Concepts of Foraminiferal Paleoecology

Studies of modern foraminiferal ecology have provided at least 5 distinct criteria for the reconstruction of marine paleoenvironments: (1) both the number of species and specimen abundance increase away from shore and with increasing depth of water to maximum values on the outer shelf and in the upper and middle bathyal zone; (2) diverse porcelaneous species are abundant in shoal near-shore marine environments; (3) arenaceous Foraminifera with simple interiors may be abundant in shallow waters whereas more complex types with labyrinthic interiors are more characteristic of bathyal depths; (4) deposition of planktonic species occurs most abundantly on the outer shelf and in the upper bathyal zone, with even greater abundances in deeper waters under the right conditions; an (5) similar environmental adaptations of modern species and fossil homeomorphs (and isomorphs) may be assumed, especially for groups of species. Faunal contamination or mixed faunas must be recognized as an ever-present deterrent to valid stratigraphic and paleoecologic analyses. One important type of contamination is the displacement of shoal faunas into deeper water; however, the displacement problem is minimized by selecting the deepest bathymetric indicator species in each sample. Another type of mixed fauna is produced by the reworking of faunas from older strata into younger sediments. This type of contamination usually is recognizable by differences in preservation or incongruous mixtures of index species of different ages or both. To test the value of foraminiferal ecology to the finding of oil deposits, a detailed study was made of the biofacies of the Middle Tertiary of the San Joaquin Valley, California. The analyses of more than 5,000 samples (cores) made it possible to construct a series of paleobathymetric maps showing the gradual evolution of the San Joaquin basin. Examples of this study are presented to illustrate the methods of applied paleoecology and their implications.

Distribution of foraminifera and sediments, Peru-Chile trench area

Abstract Eighteen trawl samples, one Petersen grab, and thirteen Phleger cores were collected between depths of 179 and 6250 m in the Peru-Chile Trench area off the west coast of South America. Sediments are mainly olive-green silt, clay and colloidal material; however, four cores contain significant amounts of either sand-sized foraminifera or shale fragments, and one of these cores is mainly white volcanic ash. Values for organic carbon and nitrogen are much higher in the bathyal than in the abyssal zone. Sediment grain sizes do not exihibit definitive trends with either depth or distance from shore. Calcium carbonate contents decrease sharply below 3500 m, reflecting reduced quantities of calcareous foraminifera in the Trench. Radiolarians are usually more than twice as abundant as foraminifera deeper than 1500 m. Foraminifera larger than 0·5 mm were concentrated in the trawl samples and are mainly arenaceous types below 1000 m. Among the smaller foraminifera, calcareous forms predominate down to 2000 m; at greater depths calcarenus-arenaceous ratios fluctuate extremely. Tests of planktonic foraminifera are most abundant in the bathyal zone. Bathymetric foraminiferal zonation is based upon upper limits of occurrence for both the larger live foraminifera from the trawls and the smaller foraminifera from the cores. Maximum size of the larger foraminifera is usually between 1 and 10 mm. The zonation is: Trawls Cores 1. 179 M Valvulineria inflata Group 2. 878 M Cibicides wuellerstorfi and 796 M Epistominella pacifica smithi Group Reophax scorpiurus Groups 1171 M Cyclammina cancellata Group 1171 M Uvigerina peregrina dirupta Group 4 1863 M Alveolophragmium subgloobosum and 1932 M Eponides tumidulus-Uvigerina Reophax nodulosus Groups Hispida Group 5. 2489 M. Hormosina ovicula Group 2489 M Nonion pompilioides Group 6. 3149 M Planispirinoides bucculenta Group M Stilonstomella antieea Group 7. 3404 M Recurvoides turbinatus-Bathysiphon Group Estimates of the total volumes of material caught by each trawl range 2 to about 43 kg, dry wt. Species restricted to deep water appear to have evolved from depth-tolerant ancestors.

Origin and Development of Globorotalia (Turborotalia) Pachyderma (Ehrenberg)

Planktonic foraminifera, morphology indicates species derived from G. (T.) continuosa in Neogene (upper N12)

Reflector Horizons and Paleobathymetric History, Eastern Panama

Basement rocks of eastern Panama, exposed around the Golfo de San Miguel, include dense well-preserved pillow basalt and diabase which are overlain by deformed chert and thin-bedded siliceous radiolarian-rich abyssal oceanic sedimentary rocks of Late Cretaceous (in part, early Campanian) age. This basalt-chert relation of the Late Cretaceous is approximately correlative with the lower reflector horizon of the deep oceans. A second abyssal volcanic phase with radiolarian-rich sediments occurs in the lower and middle parts of the Morti Tuffs, early to middle Eocene in age, which represents the equivalent of the upper reflector horizon in the deep oceans. A third abyssal volcanic phase associated with radiolarian-rich tuffaceous sediments, with some chert and agglomerate, occurs in the middle Oligocene to lower Miocene formations; this sequence has not been identified as a specific reflector in deep-sea sections. A deep-marine erosional or nondepositional interval occurs between the Late Cretaceous basement rocks and the Eocene Morti Tuffs; a second hiatus separates the Morti Tuffs from the overlying middle Oligocene to lower Miocene Pacific Tuffs and Clarita Limestone. In eastern Panama, the development of a Panamanian ridge or block is shown by the progressively shallower water facies during the middle and later Neogene, leading to paralic and nonmarine facies of the Pliocene-Pleistocene. Cessation of interoceanic communication occurred gradually during this phase, terminating finally in the Pliocene-Pleistocene. This paleobathymetric development is likely similar to that for nearby northwestern Colombia; it is in distinct contrast to the developmental history of the Canal Zone region where deep-ocean sedimentation was terminated in the middle Eocene. These middle Eocene shallower water facies of the Canal Zone may have been the source for displaced shallower water facies that are intermixed in some cases with deep-water Eocene facies of eastern Panama.

Cretaceous planktonic foraminiferal zonation

Radiometric data and phylogenetic analysis of Cretaceous planktonic foraminifera suggest that the Cretaceous be divided into three epochs rather than two. Primitive globigerines occur in the Lower Cretaceous, ingle-keeled Rotalipora faunas characterize the Middle Cretaceous, and single-keeled and double-keeled Globotruncanafaunas typifv the Upper Cretaceous. Keels arose in three independent generic lines of development in the Upper Cretaceous. Long-ranging tropical species are restricted to very short stratigraphic ranges toward the tropical boundaries defined by Globotruncana-Rotalipora lines. Cretaceous planktonic foraminiferal zonation

Distribution of Recent Foraminifera Off West Coast of Central America

A survey was made of the foraminiferal distribution in the sediments off the west coast of Central America, between depths of 6 and 6,270 feet. Thirty-six samples were examined from areas off Acapulco, off the Gulf of Fonseca, and from the Gulf of Panama. A few of the samples represent intervening areas. The composite frequency distribution of Foraminifera is plotted against changes in depth, temperature, and salinity. Faunal zones are recognized as follows. Inner Shelf fauna (0-150 feet): Elphidium spp., miliolids, Nonionella basispinata, streblus spp. Outer Shelf fauna (151-400 feet): Discorbis panamensis, Planulina ornata, Uvigerina (striate species). Upper Bathyal fauna (401-2,000 feet): Bolivina acuminata, Bolivina seminuda vars., Epistominella bradyana. Middle Bathyal fauna (2,001-4,000 feet): Bolivina spp., Bolivinita minuta, Bulimina affinis, Bulimina spinifera, Buliminella exilis tenuata, Cassidulina delicata,Chilostomella ovoidea, Uvigerina peregrina, Valvulineria inaequalis. Lower Bathyal fauna (4,001-6,270 feet): Bulimina clava, Cassidulinoides tenuis, Pullenia bulloides, Pyrgo murrhina, Uvigerina proboscidea, Valvulineria araucana, Virgulina nodosa. Associated offshore trends include: (1) increase in number of species away from shore; (2) increase in foraminiferal number out to the upper bathyal zone and a decrease beyond; (3) greatest abundance of plankton in the outer shelf zone; (4) and abundant Radiolaria and diatoms below depths of 4,000 feet.

Middle Tertiary Basin Development, San Joaquin Valley, California

An analysis was made of the foraminiferal paleoecology of the middle Tertiary in wells of the San Joaquin Valley, California. This province, which represents the southern half of the Great Valley of California, is bounded on the east by the Sierra Nevada, on the south by the Tehachapi Mountains, on the west by the Coast Ranges, and on the north it joins the Sacramento Valley near Stockton. The marine basin of this study is known as the San Joaquin Basin, and it is located in the southern half of the San Joaquin Valley. Thirteen biofacies are established for the recognition of thirteen paleobathymetric zones between depths of 0 and more than 6000 feet. In the Oligocene and lower Miocene, maximum water depths of the marine basin were abyssal, in excess of 6000 feet; basin filling brought about a decrease to lower bathyal depths during the middle Miocene; rapid sedimentation during the later Miocene resulted in shoaling of the basin to neritic depths in latest Miocene and Pliocene. Most of the better zonal index species are bathyal or lower neritic types; those with the longest stratigraphic ranges appear to be the abyssal and upper neritic assemblages. The primary deep-water connection between the San Joaquin Basin and oceanic waters to the west was consistently at the southwestern corner of the basin across the San Andreas fault. Evidence for this is the continuous dominance of deep-water facies in the southern part of the basin extending westward to the San Andreas fault. Further support is to be seen in the restriction of planktonic foraminiferal facies and radiolarians to the southern areas. Frequencies of planktonic foraminiferans are generally greatest in the southern area near the San Andreas fault, showing decreasing values away from the San Andreas fault around the southern part of the basin in a counterclockwise direction. This pattern indicates that the principal oceanic current entered the basin across the San Andreas fault and moved in a counterclockwise pattern during most of the middle Tertiary. Biofacies to the west of the San Andreas fault do not generally indicate a continuation of deep-water conditions there; right-lateral movements on the San Andreas fault have probably moved the western continuation of these deep-water basin facies far to the north. A comparison of subsidence and sedimentation rates shows about subequal rates at first in the Oligocene, somewhat greater rates of deposition than subsidence during most of the Miocene, and far greater rates of deposition than subsidence in the later Miocene. Throughout the middle Tertiary various tectonic blocks within the San Joaquin Basin apparently moved independently and continuously. More than 5000 cubic miles of rock represent the marine sediment deposited in the San Joaquin Basin during the middle Tertiary stages. Of this amount, more than 4000 cubic miles were deposited in depths of water greater than 300 feet, and most of the oil produced in the basin comes from these strata.

Cycles in Neogene paleoceanography and eustatic changes

Abstract A characteristic indicator of Antarctic and Arctic waters today is the sinistrally-coiled Globigerina pachyderma . By tracing this indicator back through the Neogene, it is possible to demonstrate major expansions of cold-water isotherms not only during the Quaternary, but also during the Middle Pliocene and the later Miocene. Expansions of cold-water isotherms of the Quaternary are correlated with the classic expansions of ice masses during the Pleistocene; those cold-water expansions of the Middle Pliocene and later Miocene suggest increases in ice masses with associated lowered sea levels, although perhaps not of the same magnitude as those of the Pleistocene. The Antarctic and Greenland ice masses were likely much more extensive during all of these colder cycles than now. Major cycles of expanded cold-water isotherms were almost certainly associated with eustatic reductions in sea level, that in turn produced marine regressions in paralic environments. Thus, there should be regressive cycles associated with the expansion of cold-water isotherms within the later Miocene, the Middle Pliocene, and those of the classic Quaternary. In the absence of complications due to variable rates of sedimentation and tectonism, shallow water depositional sites may show an Upper Miocene nonmarine phase or unconformity, a Lower Pliocene marine phase, a Middle Pliocene nonmarine phase or an unconformity, an Upper Pliocene marine phase, and a major regression at the beginning of the Quaternary. A re-evaluation of Neogene marine sections is suggested. It may be possible that the transgressive facies of the Calabrian of Italy correlates with the later Pliocene of California and is older than 3 × 10 6 years.

Miocene-Pliocene Boundary in the Philippines as Related to Late Tertiary Stratigraphy of Deep-Sea Sediments

Planktonic foraminiferal trends across the Miocene-Pliocene boundary in the Philippines suggest that sections of eight deep-sea cores reported to be Pliocene are actually latest Miocene, and that a marked extinction of discoasters in the deep-sea cores is due to an unconformity, separating Miocene and Pleisto-cene sediments, representing a time gap of some 10 million years of Pliocene time.

Alaskan Upper Miocene Marine Glacial Deposits and the Turborotalia pachyderma Datum Plane.

ln southeastern Alaska the first marine evidence of widespread glaciation occurs in Miocene sections near the base of the Yakataga Formation. An associated temperature decrease of about 10�C is indicated by the influx of an upper Miocene cold-water planktontic foraminifer, Turborotalia pachyderma, an event that occurred about 13 million years ago.