Martin B. Lagoe

Recent benthonic foraminiferal biofacies in the Arctic Ocean

Analysis of Recent foraminiferal distribution patterns for the Amerasian Basin and the adjacent continental shelves indicate 3 major biofacies: the Trochammina nana biofacies (17-350 m), the Cassidulina teretis biofacies (350-900 m) and the Stetsonia horvathi biofacies (below 900 m), with the T. nana and S. horvathi biofacies divided into subfacies. Water mass properties appear to play the dominant role in controlling the distribution of the biofacies. Recent benthonic foraminiferal biofacies in the Arctic Ocean

Oligocene through Pliocene Foraminifera from the Yakataga Reef Section, Gulf of Alaska Tertiary Province, Alaska

Oligocene through Pliocene foraminifera in the Yakataga Reef section, Gulf of Alaska Tertiary Province, help reconstruct the depositional history of the upper Poul Creek and lower Yakataga formations. Biofacies patterns reflect middle bathyal conditions during the Oligocene and Early Miocene, a Middle Miocene hiatus and upper bathyal to shelfedge depths during the Late Miocene and Early Pliocene. A regressive episode in the lowermost Yakataga Formation may represent a terminal Miocene event. Surface water temperatures during the Late Miocene-Early Pliocene change upsection from cold subarctic to cool temperate. The foraminifera also indicate that the Poul Creek-Yakataga Formation contact is Late Miocene. Oligocene through Pliocene foraminifera from the Yakataga Reef section, Gulf of Alaska Tertiary Province, Alaska INTRODUCTION Objectives The Gulf of Alaska Tertiary Province contains an impressive accumulation of Middle and Late Cenozoic marine rocks (7500 m, 25,000 ft; Miller, 1957). In the Yakataga District this accumulation is represented by two major marine units-the Poul Creek and the Yakataga formations. Study of these rocks can provide important insights into the geologic, climatic, and tectonic history of the northeast Pacific margin. The Yakataga Reef section (text-fig. 1) is a useful reference for studying the Middle Cenozoic rocks of the Yakataga District. This tidewater section exposes a relatively unweathered and accessible sequence of rocks across the contact of the Poul Creek and Yakataga formations. The objectives of this study are to: 1) document the major foraminiferal trends in the Yakataga Reef section; 2) briefly describe the major lithologic units in the Yakataga Reef section; 3) infer the paleoenvironments in which the rocks were deposited; 4) determine provisional biostratigraphic units for use in a general study of the Miocene of the Yakataga District (Lagoe, in preparation); 5) determine the age of the Poul Creek/Yakataga contact at Yakataga Reef.

Paleogeography of Monterey Formation, Cuyama Basin, California

The Cuyama Basin is one of several discrete, middle Cenozoic basins that formed a continental borderland in the coastal California province during the Miocene. The Monterey Formation is lithologically and stratigraphically complex. It varies widely in thickness, up to 4,500 ft (1,400 m), reflecting variable subsidence within the basin. Thinning over anticlines and the Cox fault zone suggests structural movement occurred contemporaneously with sedimentation, beginning in the late Saucesian (early Miocene). The age of the Monterey Formation also varies, becoming younger to the northwest. Areas of maximum subsidence migrated from southeast (Cuyama Valley) to northwest (northern La Panza Range). Schematic paleogeographic maps constructed on 4 time slices illustrate that the depositional history of the basin reflects these subsidence patterns and various depositional controls. Late Saucesian-Relizian (early Miocene) time is characterized by relatively low sea level, maximum subsidence in the southeast, and basinal sedimentation varying from calcareous biogenous sediments to sandy submarine fan deposits. Luisian-early Mohnian (middle Miocene) patterns reflect high sea level, maximum subsidence in the northwest, and basinal sediments of a calcareous or siliceous biogenous nature. Finally, the entire southern Salinian block shoaled to shallow marine or nonmarine conditions by the end of Mohnian (late Miocene) time.--Modified journal abstract.

Holocene Development of the Southeastern Texas Coast, Sabine Lake Area, from Foraminiferal Biofacies

ABSTRACT Foraminifera were analyzed in cores of Holocene sediments from the southeastern Texas coast to better understand the post-glacial evolution of the Texas chenier plain and incised valley of the Sabine and Neches Rivers. Foraminifera are rare to absent in highstand interfluve marsh and in incised-valley fluvial floodplain deposits, whereas nearshore marine, estuarine, and chenier plain deposits contain abundant foraminifera. Overall foraminiferal diversity is low, and sample assemblages are dominated by Ammonia parkinsoniana and Elphidium gunteri. These species comprise about 78% of the fauna; the remaining taxa include Elphidium spp., miliolids, Brizalina spp., Bucella hannai, and Palmerinella palmerae. Samples are characterized by mixtures of well-preserved and poorly-preserved tests. This, along with the presence of Cretaceous foraminifera, suggests that many of the microfossils are reworked. Small adult foraminifera are common in cores from the chenier plain and are generally associated with fine-grained sediments deposited as mudflats between the sand-rich beach-ridges. Agglutinated foraminifera are surprisingly rare probably because geochemical conditions do not favor the preservation of agglutinated tests below about 2 m. Foraminiferal biofacies include a very low diversity, brackish (marsh) assemblage, a moderate diversity beach assemblage, a moderate diversity shallow marine assemblage, and a relatively high diversity, slightly deeper (but still nearshore) marine assemblage. These biofacies are consistent with those described from the Louisiana chenier plain. The faunal associations, diversity, abundance, and preservation provide insight to the paleoenvironments and depositional processes of the chenier plain.

Interregional correlation of benthic foraminiferal faunas along the northeast pacific margin—climatic controls

Abstract Similarity of benthic foraminiferal faunas from the Gulf of Alaska Tertiary Province and central California fluctuates during the middle Cenozoic, being highest (most similar) in the late Eocene and again in the early Miocene. A major lineage of benthic foraminifera, the uvigerinid—siphogenerinid, extends its range northward into the Gulf of Alaska at these times. These relationships can be correlated to climatic fluctuations as defined by oxygen isotopic analysis. Increased faunal cosmopolitanism during warm climatic periods increases the geographic extent to which benthic foraminiferal correlations can be made. During cold climatic periods faunal endemism increases and correlations become more difficult or impossible. Consideration of the effects of climate on faunal distributions, combined with detailed analysis of local paleoenvironmental influences, provides a basis for better evaluating both interbasinal and interregional foraminiferal correlations.

Late Holocene Foraminiferal Biofacies from Baffin Bay, Texas: Preliminary Analysis of a 4,000-Year Record of Paleosalinity

ABSTRACT Predominant hypersalinity in Baffin Bay, Texas, leads to the preservation of laminated sediments. These largely unbioturbated sediments permit reconstruction of a high-resolution, late Holocene paleoenvironmental record. Piston cores from the center of Baffin Bay recovered up to 5 m (16.4 ft) of these fine-grained sediments. On the basis of previous dating of dolomite layers and sedimentation rate estimates (ca. 1 mm/yr), these cores represent up to 4,000 yr of deposition. Preliminary micropaleontological analysis of core L593-2 (4.9 m [16 ft] long) is based on 120 samples with an average sample spacing of 3-4 cm. Foraminiferal assemblages are dominated by three major taxonomic groups: (1) Ammonia parkinsoniana; (2) Elphidium spp.; and (3) miliolids (mostly Quinqueloculina spp. and Triloculina spp.). Previous work on modern microfaunas in Texas embayments shows that each of these groups may dominate benthic faunas under different environmental conditions. Miliolids dominate hypersaline environments, whereas the other two groups will tolerate moderately brackish water. Accordingly, core samples dominated by miliolids are interpreted to represent the most hypersaline conditions. Samples dominated by Ammonia parkinsoniana represent the most brackish salinities encountered in the core (but greater than 20 ppt). Dominance of benthic assemblages varies dramatically within the core. Major biofacies trends include (1) no occurrence of either low-salinity, agglutinated or open shelf assemblages; (2) peaks in miliolid abundance that define paleosalinity fluctuations on a scale of 10 to 30 cm in the upper 4.2 m (13.8 ft) of the core (thus representing cyclicity on the scale of hundreds of years); and (3) very rare or no miliolids from 4.2 to 4.9 m, suggesting an absence of hypersalinity, but still oceanographically restricted conditions. The core did not penetrate sediments deposited prior to restriction of Baffin Bay by Padre Island (ca. 5,000 yr B.P. Three dolomite layers within the core (at 2.86 m, 4.34 m, and 4.71 m) occur in intervals with rare or no miliolids, arguing against a hypersaline setting for their formation. Ongoing work on these sediments includes AMS carbon-14 dating to better constrain sediment accumulation rates and quantitative analysis of the benthic foraminiferal data by transfer functions, in order to derive quantitative paleosalinity estimates.

Benthic Foraminiferal Biofacies in Stevens Sandstone: Relationships to Water-Mass Oxygen Levels in Late Miocene San Joaquin Basin, California: ABSTRACT

The Stevens sandstone is an extensive and complex sequence of late Miocene turbidite sandstone and mudstone within the Monterey Formation of the San Joaquin basin. To date, the paleoenvironmental analysis of benthic foraminifera in such facies is limited largely to general inferences of paleobathymetry. A different approach uses multivariate analytical methods to classify biofacies and interpret them with respect to modern ecologic concepts derived from studies of Holocene faunas in the southern California borderland. Cluster and factor analysis help define 4 recurrent biofacies in the Coles Levee area: an agglutinated species biofacies (ASB), Uvigerina subperegrina biofacies (USB), Bolivina vaughani biofacies (BVB), and mixed calcareous biofacies (MCB). Ordination (princ pal components) plots of environmentally significant species indicate that the biofacies reflect a gradient in oxygen concentration of late Miocene water masses. The BVB and MCB represent the highest oxygen levels, the USB low but not dysaerobic levels, and the ASB the lowest oxygen concentrations. Ordination also shows that downslope transport of faunas and carbonate dissolution are also important in forming Stevens biofacies. Stratigraphic distribution of biofacies defines systematic shifts in oxygen concentration, probably linked to climate. These late Miocene biofacies variations were previously attributed to paleobathymetric changes. The distribution of species not restricted to the defined biofacies, plus the paleoenvironmental analysis presented here, argues against paleobathymetr as a complete explanation. This analytical approach shows the potential for greatly increasing our understanding of foraminiferal biofacies in submarine-fan environments. End_of_Article - Last_Page 277------------

Distribution and Depositional History of Neogene Phosphorites Along Pacific Coast of North America: ABSTRACT

Pelletal and nodular phosphorites occur commonly to abundantly in neritic (shelf) and bathyal (slope) deposits of uppermost Oligocene (25 Ma) to upper Miocene (10 to 7 Ma) age from 23°N on the peninsula of Baja California, Mexico, to 39°N near Point Arena, northern California, encompassing a belt of deposition about 1,430 mi (2,300 km) in length. In addition, pelletal phosphorite sands are commonly present within adjacent middle and lower bathyal deposits of similar age range representing redeposited material in conduits, feeding basins, and submarine fans. In some areas, pelletal phosphorites reach 200 ft (60 m) in thickness. Mining of Miocene phosphorites is now well under way in Baja California. The age of peak formation and accumulation of Pacific Coast phos horites appears to become younger from south to north implying variations in patterns of upwelling and/or eustatic, climatic, and tectonic control of shelf character and flux of terrigenous clastics to the margin. Later reworking of the Miocene deposits has allowed reconcentration of the phosphorites in adjacent Pliocene, Pleistocene, and Holocene neritic units. Paleontologic, isotopic, and sedimentologic evidence indicate that the widespread Neogene phosphorites formed under a special set of climatic, oceanographic, eustatic, and tectonic conditions associated or coincident with a major climatic threshold occurring in mid-Miocene (15 Ma) time and commencement of a glacial climatic state. Three key factors were apparently responsible for allowing the unusually prolific formation of Miocene phosphorites as well as simultaneous widespread deposition of diatomaceous sediments in this region including (1) vigorous upwelling of nutrient-rich water and accelerated productivity as a function of deteriorating Neogene climate, (2) associated development of intense oxygen minima impinging against the various slope and shelf areas creating appropriate b ogeochemical conditions for phosphorite precipitation, and (3) the absence or severe reduction in delivery of terrigenous clastics to sites of phosphorite precipitation as a function of Neogene eustatic, climatic, and tectonic events. End_of_Article - Last_Page 1691------------

Miocene Geologic History of Southern Salinian Block, California--Perspectives from a Stratigraphic Study of Monterey Formation: ABSTRACT

A better understanding of the Miocene geologic history of the southern Salinian block is aided by a stratigraphic and paleoenvironmental study of the Monterey Formation. Extensive subsurface and surface data enable construction of isopach, paleobathymetric, age-relationship, and paleogeographic maps that document the depositional history of the Monterey Formation. Isopach maps show that the formation ranges up to 1,400 m (4,500 ft) thick beneath Cuyama valley. Other areas of maximum accumulation occur in the northwest Caliente Range and the Indian Creek area. Offset of isopachs north of Barrett Ridge suggests approximately 15 km (9 mi) of post-middle Miocene right slip on the San Juan fault. Age-relationship maps of the upper and lower contacts of the Monterey Formation for the area from Cuyama Valley to the northern La Panza Range indicate that both the top and base of the formation become younger toward the northwest--the base ranging from Saucesian to Relizian and the top from Relizian to Mohnian. Paleobathymetric maps, based on the distribution of benthic Foraminifera, are plotted on four time slices: late Saucesian, Relizian, Luisian, and early Mohnian. These maps also indicate that the Cuyama basin filled from the southeast to the northwest, and they reflect the migration of maximum subsidence in that direction during the Miocene. The relationship of general stratigraphy to structural features in the Cuyama basin shows that certain faults and anticlines were active during the deposition of the Monterey Formation. Specifically, the Cox fault zone and South Cuyama End_Page 1693------------------------------ anticline show evidence of such movement, beginning in the early Miocene, which affected the distribution of the formation. These relationships reflect an episode of structural deformation preceding the late Neogene episode associated with movement on the San Andreas fault system, and they may be related to the earliest activity on this system. End_of_Article - Last_Page 1694------------

Subsurface Facies Analysis of Saltos Shale Member (Miocene), Monterey Shale, Cuyama Valley, California: ABSTRACT

Distributional analysis of the lithology, sedimentary structures, and microfauna in core samples from oil wells in Cuyama Valley allows recognition of distinctive lithofacies and biofacies in the Saltos Shale Member of the Monterey Shale. Depositional environments are determined from the interpretation of these lithofacies and biofacies. The distribution and character of the depositional environments record the basin-history for this part of the Cuyama basin during the late Saucesian through Luisian (late early to middle Miocene). Middle bathyal, fine-grained, base-of-slope clastics predominate during the Saucesian. Intercalated, thin-bedded, turbidite sandstones are prominent in some well sections and sand/shale ratios help indicate a source to the north or northeast. Relizian depositional environments are more varied, ranging from middle bathyal shales and siltstones in the area just to the east of South Cuyama oil field, to nonmarine sandstone, conglomerate, and mudstone in eastern Cuyama Valley. The distribution of these depositional environments was controlled partly by contemporaneous tectonic activity as evidenced by depositional thinning over structural highs, abrupt thickening across at least one fault, and progradation of the shelf from the east. By Luisian time the eastern Cuyama Valley area was char cterized by shelf-to-nonmarine deposition. This is in marked contrast to upper bathyal diatomaceous mudstones and diatomites which accumulated in a low-oxygen environment immediately to the west, in the vicinity of Whiterock Bluff. The Monterey Shale is overlain by the shallow-water Santa Margarita Formation (late Miocene), which marks the final phase of marine sedimentation in the Cuyama basin. End_of_Article - Last_Page 946------------