First Findings of Fossil Pollen of the Genus Decodon in the Oligocene and Miocene in the South of Western Siberia and Their Paleobiogeographical Distribution Features

The results of palynological study of the reference section of upper Paleogene and Neogene deposits of the Kulunda Plain, exposed by borehole 2 (settlement Ozeryanka, Novosibirsk Oblast) are presented. In the Tavda Formation, a dinoflagellate cysts assemblage of late Priabonian age and a palynoassemblage with Quercus gracilis–Q. graciliformis of the late Eocene were identified. Nine palynoassemblages have been identified from continental Oligocene and Neogene deposits: Carya spackmania–Carpinus perfectus–Tilia of the beginning of the second half of early Oligocene; Betula–Corylus–Pinus s/g Haploxylon of the second half of early Oligocene; Juglans sieboldianiformis–Pterocarya stenopteroides–Fagus of the end of the early Oligocene, possibly the beginning of the late Oligocene; Castanea–Quercus–Myrica of late Oligocene; Pinus s/g Haploxylon–Abietinieaepollenites sellowiiformis–Cupressaceae of early Miocene, presumably the end of late Oligocene; Alnus–Ulmus–Polypodiales of early–middle Miocene; Betula–Quercus–Ulmus of middle Miocene and Alnus–Polypodiales–Sigmopollis of middle–late Miocene; Betula–Artemisia–Amaranthaceae of late Miocene. Layers with freshwater dinocysts Pseudokomewuia sp. 1 were found at the top of the Zhuravka Formation. The deposition environment in the late Eocene, Oligocene and Miocene in the south of the West Siberian Plain has been reconstructed. The marine transgression in the Priabonian extended to the north of the modern Kulunda Plain. The first half of the Early Oligocene in the region experienced a hiatus. After a significant cooling at the Eocene–Oligocene boundary, climatic conditions again became warm and humid as evidenced by the distribution the growth of mesophytic coniferous-broadleaf forests with hickory. In the second half of the early Oligocene, the climate became colder and more humid, and the proportion of elements of the Arcto- Tertiary flora increased in plant communities. During the end of the early Oligocene and the late Oligocene, the climate became warmer, and broadleaf trees dominated the forests. At the end of the late Oligocene, the climate again became more humid, but remained warm, and pine forests predominated in phytocenoses, with the participation of ancestral forms of modern Cathaya. The cooling at the turn of the late Oligocene–early Miocene led to the predominance of conifers in forests; in the early Miocene, the proportion of small-leaved tree species increased sharply, and the participation of pine trees decreased. In the middle Miocene, the climate remained quite warm, but drier, and cypress trees disappeared from the plant communities. In the late Miocene, open plant communities are formed.

Data on spores, pollen, and dinoflagellate cysts studied in composite section of Oligocene-Miocene deposits in southern part of West Siberia are presented. Eleven biostratigraphic units distinguished in the section are ranked as palynozones and beds with palynological assemblages. Palynological data substantiate age of deposits and specify ranges and boundaries of palynozones. Based on dinocyst assemblages first studied in sediments of the Zhuravka and Abrosimovo horizons (upper Oligocene, lower Miocene), the Pseudokomewuia Beds are included into local stratigraphic scheme. According to results of comparative analysis, similar and distinctive features of Oligocene-Miocene dinocyst assemblages from West Siberia, China and North America are elucidated. Based on palynological data, the local stratigraphic scheme of higher resolution is suggested for subdivision of Oligocene and Miocene deposits in southern part of West Siberia (Baraba and Kulunda lithofacies regions).

In the Cuu Long basin, three source beds are identified: lower Miocene, Upper Oligocene, upper Eocene + lower Oligocene. They are separated from each other by sand-clay layers. Only Upper Oligocene and Upper Eocene + Lower Oligocene source beds are two main source beds supplying a great part of organic matter into traps. Petroleum source potential of Upper Oligocene source bed (66.30 billion tons) is greater than Upper Eocene + Lower Oligocene bed (29.88 billion tons). Total amount of hydrocarbon has ability to take part in accumulation process at the petroleumbearing traps from Upper Oligocene and Upper Eocene + Lower Oligocene source beds is over 2.19 billion tons and below 1.16 billion tons respectively. Thus, in whole CuuLong basin, source rocks have capacity to produce 96.18 billion tons of hydrocacbon in which accumulation is 3.35 billion tons making up 3.35% production quantity. Applying Monte - Carlo simulation method, using Crystal Ball software to calculate production potential and total amount of organic matter taking part into migration and accumulation process give rather appropriate result with difference level ≤ 1.25%.. Prospecting levels are in the following order: (i)Central lift zone has the greatest prospects, next is Dong Nai lift zone, graben located in north west inclined slope, south east inclined slope, north east area of Tam Dao lift zone finally. (2)Petroleum does not only accumulate in structural, combination traps but also in non-structural traps.

The paper presents floristic and geo-botanical characteristics of rare forest ecosystems of the south of Western Siberia – spruce forests on the site of the Ob river ancient bed within the modern Bolshaya Sogra within the boundaries of the state natural reserve ‘Kislukhinsky’ (Altai region). Spruce forests here are at the edge of their spread in the West Siberian Plain conditions. There are over 300 species of vascular plants found in these spruce forests. Among them are plants that are typical of the mountain taiga associations of Russian Altai, as well as orchids, which have high species diversity. Spruce forest set of associations is also varied. The uniqueness of the described communities to the south of Western Siberia, the large number of rare and endangered plant species listed in the Red Books of different ranks, as well as the boreal forest species complex rare to the lowland wooded steppe, which has a relict character, all served as the basis for allocating a special protection area in the ‘Kislukhinsky’ reserve and attributing the studied spruce forests to the forests of high conservation value.

Marine Oligocene sequences in India outcrop only in western part of Kachchh. Earlier researchers have recognized the Oligocene strata under the Nari Series (Nagappa 1959; Chatterji and Mathur 1966). The Nari Series has a type area in Pakistan. It has two subdivisions – the Lower Nari (Lower Oligocene) and the Upper Nari (Upper Oligocene). It seems that there is no valid proof about the age of the Lower Nari due to lack of proper fauna (Eames 1975), and according to Pascoe (1962), the Upper Nari slightly transgress into Aquitanian (Lower Miocene), therefore, one has to be very cautious. Biswas and Raju (1971) reclassified the Oligocene strata of Kachchh and lithostratigraphically clubbed them as the Maniyara Fort Formation with type section along the Bermoti stream. This Formation has four members. The lower three members correspond to the Ramanian Stage (Lower Oligocene, Biswas 1971, 1973) while the uppermost to the Waiorian Stage (Upper Oligocene, Biswas 1965, 1971, 1973). The Ramanian Stage is characterized by large forams especially Nummulites fichteli, Nummulites fichteli intermedius, Lepidocyclina (Eulepidina) dialata and Operculina sp. Several ostracods are also known to occur. Megafauna include bivalves, gastropods, echinoids, corals, mammals and reptiles. Concerning bivalves earlier researchers have recorded a few taxa namely Trisidos semitorta (Lamarck), Cubitostrea angulata (J de C Sowerby), Pecten (Amussiopecten) labadyei d’Archiac and Haime, Periglypta puerpera (Linne’) var. aglaurae Brongniart, Ostrea fraasi Mayer Eymer and listed Pecten laevicostatus Jd e C Sowerby, Callista pseudoumbonella Vredenburg and Clementia papyracea (Gray) from Kachchh as against overall 42 forms from the Nari Series as a whole (Vredenburg 1928). This tempted us to make an attempt to collect bivalve fauna systematically which are occurring prolifically in the Ramanian Stage. In the present work, for this purpose, sections are worked out around Lakhpat (23 ◦ 50 � N; 68 ◦ 47 � E), Maniyara Fort (23 ◦ 28 � 05 �� N; 68 ◦ 37 � E) Rakhdi Dam (23 ◦ 27 � 26 �� N; 68 ◦ 40 � 10 �� E) and Waior (23 ◦ 25 � 05 �� N; 68 ◦ 41 � 37 �� E) with a view to highlight the entombed bivalve taxa. Authors have encountered 53 species of which 23 are restricted to the Ramanian Stage.

Lithostratigraphy and planktonic foraminiferal biostratigraphy of the late Eocene-Middle Miocene sequence in the area between Wadi Al Zeitun and Wadi Al Rahib, Al Bardia area, northeast Libya

Les Coralliophilidae, Gastropoda de l'Oligocène et du Miocène inférieur d'Aquitaine (Sud-Ouest de la France): Systématique et coraux hôtes

Neogene stratigraphy and paleoenvironments of China

Calcareous nannoplankton are abundant in some rocks assigned to the California microfaunal stages. Most species are stratigraphically long ranging, although some have restricted stratigraphic ranges in low-latitude tropical regions. These species permit partial correlation of the California stages with the widely recognized plankton biostratigraphic zones of the tropics. The upper Zemorrian is correlative with the Sphenolithus distentus through the lower Triquetrorhabdulus carinatus (NP 24-NN1) zones (upper Oligocene) the Saucesian with the upper T. carinatus through the lower Helicopontosphaera ampliaperta (NN1-4) zones (lower Miocene), the Relizian with the upper H. ampliaperta through the lower S. heteromorphus (NN4-5) zones (lower-middle Miocene), the Luisian with the upper S. heteromorphus through Discoaster kugleri (NN5-7) zones (middle Miocene), and the Mohnian with the Catinaster coalitus through D. calcaris (NN8-10) zones (middle-upper Miocene). The species diversity of nannofossils in the California Oligocene-Miocene rocks is low. Like the planktonic Foraminifera from the same rocks, the nannofossils are analogous to species now living in the modern transitional water mass off California. There are no elaborate species as in the tropics and the floras tend to be dominated by single species (i.e., Coccolithus). These observations indicate that California was under the influence of a current flowing southward, with velocities nearly that of the modern California Current. The dominance of the assemblages by a single species, as well as other evidence from the rocks, indicates that upwelling was likely as important during the Miocene as it is today. End_of_Article - Last_Page 436------------

Research Article| July 01, 1983 The Walvis Ridge transect, Deep Sea Drilling Project Leg 74: The geologic evolution of an oceanic plateau in the south Atlantic Ocean THEODORE C. MOORE, Jr.; THEODORE C. MOORE, Jr. 1Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island 0288115Present addresses: Exxon Production Research Co., Houston, Texas 77001; (Borella) Saddleback College, Mission Viejo, California Search for other works by this author on: GSW Google Scholar PHILIP D. RABINOWITZ; PHILIP D. RABINOWITZ 2Texas A&M University, Department of Oceanography, College Station, Texas 77843 Search for other works by this author on: GSW Google Scholar ANNE BOERSMA; ANNE BOERSMA 3Lament-Doherty Geological Observatory, Columbia University, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar PETER E. BORELLA; PETER E. BORELLA 4Deep Sea Drilling Project, A-031, Scripps Institution of Oceanography, La Jolla, California 9209316Present addresses: Saddleback College, Mission Viejo, California Search for other works by this author on: GSW Google Scholar ALAN D. CHAVE; ALAN D. CHAVE 5Geological Research Division, A-015, Scripps Institution of Oceanography, La Jolla, California 92093 Search for other works by this author on: GSW Google Scholar GERARD DUEE; GERARD DUEE 6Laboratoire Geologic Stratigraphique, Universite des Sciences et Techniques de Lille, 59650 Villeneuve D'Ascq, France Search for other works by this author on: GSW Google Scholar DIETER K. FUTTERER; DIETER K. FUTTERER 7Geologisch-Palaontologisches Institut und Museum der Universitat Kiel, Olshausenstrasse 40/60, 2300 Kiel, Federal Republic of Germany Search for other works by this author on: GSW Google Scholar MING JUNG JIANG; MING JUNG JIANG 8Department of Oceanography, Texas A&M University, College Station, Texas 7784317Present addresses: Robertson Research Laboratories, Houston, Texas 77060 Search for other works by this author on: GSW Google Scholar KLAUS KLEINERT; KLAUS KLEINERT 9Geologisches Institut der Universitat Tubingen, Sigwartstrasse 10, D7400 Tubingen 1, Federal Republic of Germany Search for other works by this author on: GSW Google Scholar ANDREW LEVER; ANDREW LEVER 10School of Environmental Sciences, University of East Angila, Norwich NR4 7TJ, United Kingdom Search for other works by this author on: GSW Google Scholar HELENE MANIVIT; HELENE MANIVIT 11Laboratoire de Palynologie, BRGM, B.P. 6009, F-45018 Orleans 4646 Cedex, France Search for other works by this author on: GSW Google Scholar SUZANNE O'CONNELL; SUZANNE O'CONNELL 12Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 0254318Present addresses: Lamont-Doherty Geological Observatory, Columbia University, Palisades, New York 10964 Search for other works by this author on: GSW Google Scholar STEPHEN H. RICHARDSON; STEPHEN H. RICHARDSON 13Department of Earth & Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 Search for other works by this author on: GSW Google Scholar NICHOLAS J. SHACKLETON NICHOLAS J. SHACKLETON 14Godwin Laboratory, University of Cambridge, Free School Lane, Cambridge, England CB2 3RS Search for other works by this author on: GSW Google Scholar Author and Article Information THEODORE C. MOORE, Jr. 1Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island 0288115Present addresses: Exxon Production Research Co., Houston, Texas 77001; (Borella) Saddleback College, Mission Viejo, California PHILIP D. RABINOWITZ 2Texas A&M University, Department of Oceanography, College Station, Texas 77843 ANNE BOERSMA 3Lament-Doherty Geological Observatory, Columbia University, Palisades, New York 10964 PETER E. BORELLA 4Deep Sea Drilling Project, A-031, Scripps Institution of Oceanography, La Jolla, California 9209316Present addresses: Saddleback College, Mission Viejo, California ALAN D. CHAVE 5Geological Research Division, A-015, Scripps Institution of Oceanography, La Jolla, California 92093 GERARD DUEE 6Laboratoire Geologic Stratigraphique, Universite des Sciences et Techniques de Lille, 59650 Villeneuve D'Ascq, France DIETER K. FUTTERER 7Geologisch-Palaontologisches Institut und Museum der Universitat Kiel, Olshausenstrasse 40/60, 2300 Kiel, Federal Republic of Germany MING JUNG JIANG 8Department of Oceanography, Texas A&M University, College Station, Texas 7784317Present addresses: Robertson Research Laboratories, Houston, Texas 77060 KLAUS KLEINERT 9Geologisches Institut der Universitat Tubingen, Sigwartstrasse 10, D7400 Tubingen 1, Federal Republic of Germany ANDREW LEVER 10School of Environmental Sciences, University of East Angila, Norwich NR4 7TJ, United Kingdom HELENE MANIVIT 11Laboratoire de Palynologie, BRGM, B.P. 6009, F-45018 Orleans 4646 Cedex, France SUZANNE O'CONNELL 12Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 0254318Present addresses: Lamont-Doherty Geological Observatory, Columbia University, Palisades, New York 10964 STEPHEN H. RICHARDSON 13Department of Earth & Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 NICHOLAS J. SHACKLETON 14Godwin Laboratory, University of Cambridge, Free School Lane, Cambridge, England CB2 3RS Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1983) 94 (7): 907–925. https://doi.org/10.1130/0016-7606(1983)94<907:TWRTDS>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation THEODORE C. MOORE, PHILIP D. RABINOWITZ, ANNE BOERSMA, PETER E. BORELLA, ALAN D. CHAVE, GERARD DUEE, DIETER K. FUTTERER, MING JUNG JIANG, KLAUS KLEINERT, ANDREW LEVER, HELENE MANIVIT, SUZANNE O'CONNELL, STEPHEN H. RICHARDSON, NICHOLAS J. SHACKLETON; The Walvis Ridge transect, Deep Sea Drilling Project Leg 74: The geologic evolution of an oceanic plateau in the south Atlantic Ocean. GSA Bulletin 1983;; 94 (7): 907–925. doi: https://doi.org/10.1130/0016-7606(1983)94<907:TWRTDS>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Five sites were drilled along a transect of the Walvis Ridge. The basement rocks range in age from 69 to 71 m.y., and the deeper sites are slightly younger, in agreement with the sea-floor–spreading magnetic lineations. Geophysical and petrological evidence indicates that the Walvis Ridge was formed at a mid-ocean ridge at anomalously shallow elevations. The basement complex, associated with the relatively smooth acoustic basement in the area, consists of pillowed basalt and massive flows alternating with nannofossil chalk and limestone that contain a significant volcanogenic component. Basalts are quartz tholeiites at the ridge crest and olivine tholeiites downslope. The sediment sections are dominated by carbonate oozes and chalks with volcanogenic material common in the lower parts of the sediment columns. The volcanogenic sediments probably were derived from sources on the Walvis Ridge.Paleodepth estimates based on the benthic fauna are consistent with a normal crustal-cooling rate of subsidence of the Walvis Ridge. The shoalest site in the transect sank below sea level in the late Paleocene, and benthic fauna suggest a rapid sea-level lowering in the mid-Oligocene.Average accumulation rates during the Cenozoic indicate three peaks in the rate of supply of carbonate to the sea floor, that is, early Pliocene, late middle Miocene, and late Paleocene to early Eocene. Carbonate accumulation rates for the rest of the Cenozoic averaged 1 g/cm2/103 yr. Dissolution had a marked effect on sediment accumulation in the deeper sites, particularly during the late Miocene, Oligocene, and middle to late Eocene. Changes in the rates of accumulation as a function of depth demonstrate that the upper part of the water column had a greater degree of undersaturation with respect to carbonate during times of high productivity. Even when the calcium carbonate compensation depth (CCD) was below 4,400 m, a significant amount of carbonate was dissolved at the shallower sites.The flora and fauna of the Walvis Ridge are temperate in nature. Warmer-water faunas are found in the uppermost Maastrichtian and lower Eocene sediments, with cooler-water faunas present in the lower Paleocene, Oligocene, and middle Miocene. The boreal elements of the lower Pliocene are replaced by more temperate forms in the middle Pliocene.The Cretaceous-Tertiary boundary was recovered in four sites drilled, with the sediments containing well-preserved nannofossils but poorly preserved foraminifera. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Rodents of the extant family Gliridae, commonly called dormice, are common in European faunas since the early Eocene. Here we study for the first time specimens from St-Martin-de-Castillon C (France, early Oligocene) previously reported as Gliravus aff. majori and Pseudodryomys aff. fugax. We now refer them to Butseloglis tenuis and Microdyromys misonnei. Besides the French material, new specimens from Montalbán 1D (Spain, early Oligocene) are studied. They include: Butseloglis montisalbani and M. misonnei already known in the locality, but also Oligodyromys libanicus and Glirudinus aff. glirulus reported here for the first time. Previous phylogenies of the family only focused on extant taxa. Here we propose the first phylogenetic analysis of Gliridae including both extant and fossil taxa. The relationships between the taxa show several paraphylies at the generic level and suggest that the classification of the family needs a revision. Two main clades are revealed in our analysis, including most extant taxa, both of them being closely related to the Oligocene genus Microdyromys. By comparing the phylogeny to the evolution of species-richness through time, we show that glirids underwent three major diversification phases. The first diversification event involves several clades of late Eocene and early Oligocene glirids. The second diversification event involves the two main clades still represented today. They both started diversifying in the late Oligocene and led the species richness of the family to reach a peak at the end of the early Miocene. Finally, the third diversification starts in the middle Pliocene and involves mostly extant genera. These diversification phases might have been triggered by successive glaciation events that occurred in the Oligocene, Miocene and Pliocene. A potential evolutionary advantage of this family successfully facing cold climatic events could be the ability to hibernate, acquired as early as the early Oligocene.

The Paratethys area extends from Central Europe to the borders of the Caspian Sea in Central Asia and hosts a significant number of petroleum provinces, many of which have been charged by Eocene to Miocene source rocks of supra‐regional significance. These include highly oil‐prone Middle Eocene marls and limestones in the Eastern Paratethys (Kuma Formation and equivalents) which are several tens of metres thick. Estimates of the source potential index (SPI) indicate that the Kuma Formation in the northern Caucasus and the Rioni Basin (Georgia) may generate 1 to 2 tons of hydrocarbons per square metre (tHC/m2). This implies that the Kuma Formation may also be an important and additional source rock in the eastern Black Sea.Oligocene and Lower Miocene pelitic rocks (Maikop Group and equivalents) are considered to be the most important source rocks in the Paratethys. Vertical variations in source potential record different stages of basin isolation that reached a maximum during the Early Oligocene (NP23) Solenovian Event. However major variations exist between different sub‐basins in the Central and the Eastern Paratethys. In the Central Paratethys, the highest quality source rocks occur in the Carpathian Basin where the Menilite Formation, several hundreds of metres thick, can generate up to 10 tHC/m2. Locally the Menilite Formation is about 1500 m thick and continues into the Lower Miocene. In these settings, the Menilite Formation can generate approximately 70 tHC/m2. In the Alpine Foreland Basin (Schöneck and Eggerding Formations) and the Pannonian Basin (Tard Clay Formation), oil‐prone source rocks are restricted to the Lower Oligocene. In the Eastern Paratethys, the best source rock intervals of the Maikop Group are typically associated with the Early Oligocene Solenovian Event. By contrast, with the exception of the Kura Basin in Azerbaijan, the potential of Upper Oligocene and Lower Miocene rocks is often limited. In total, the Maikop Group may generate up to 2 tHC/m2 in the North Caucasus area and 4 tHC/m2 in the Rioni Basin.A particular source rock facies is found in the Western Black Sea where diatomaceous rocks with good oil potential accumulated in the Kaliakra Canyon during Early Miocene time. This facies may generate up to 8 tHC/m2, but is probably limited to shelf‐break canyons.Middle and Upper Miocene rocks are the main source for oil and thermogenic gas in the Pannonian Basin System, and also contributed to thermogenic hydrocarbons in the Moesian Platform and the South Caspian Basin. In addition, Upper Oligocene and Miocene rocks are the source for microbial gas in several basins including the Alpine and Carpathian foredeeps.

The carbon and oxygen isotopic composition of seventy-nine samples of biogenic carbonates from the Mainz Basin Tertiary (Oligocene and Lower Miocene) was analysed. Most samples were mollusc shells still consisting of aragonite. Assuming only small temperature effects, salinity trends derived from isotope data are consistent with palaeontological results from the region: a salinity cycle ranging from fresh water-brackish (Lower Oligocene) towards marine (Middle Oligocene) and brackish-fresh water (Upper Oligocene) was found. Within the Lower Miocene, a trend of decreasing salinities is suggested. Though the isotopic salinity trends coincide rather well with palaeontological salinities, the absolute oxygen isotope ratios indicate an unusual isotopic environment enriched in 18O. Isotope fractionation is explained by evaporation of a closed basin (Rupelton excluded) with fresh water influx from surrounding land areas in a subtropical climate. Enrichment in 18O by repeated evaporation processes is paralleled by increasing concentration of Sr. Increasing fresh water influx during the Oligocene is due to climatic changes with a trend of more humid conditions towards the younger rock strata.

Caliente Range and environs furnishes what is believed to be the best Miocene record for California. Approximately 180 molluscan and echinoderm faunas representing 47 nearly consecutive horizons from that of Turritella inezana var. hoffmani upward to well above that of Astrodapsis tumidus have been obtained from a Miocene succession locally about 13,800 feet in thickness. At Caliente Mountain a homoclinal section exposes, upward, successively about 1,100 feet of upper Oligocene(?), 4,500 feet of Vaqueros (lower Miocene), 4,700 feet of Temblor (middle Miocene), and 4,600 feet of Monterey (upper Miocene) strata. The marine Miocene series locally grades on the one hand to fine facies yielding foraminifers, and on the other to coarse continental facies yielding terrestrial ve tebrates. The district lies at the junction of the three largest Miocene provinces of the state, linking their histories. The area discussed formed the pivotal part of a peculiarly long, narrow, and deep upper Oligocene and Miocene trough about 300 miles in length and 20 in width which seemingly extended from the Santa Cruz region southeast to Caliente Range. At this latter place the trough forked, sending a branch east into what is now the San Emigdio foothill region of southern San Joaquin Basin, with the original strike continuing southeast to intersect and die out in Ventura Basin. A thick marine succession along the axis of the trough grades on the flanks to thin wedges separated by unconformities that appear and grow strandward. Near its heads the succession locally passes into continental deposits with similar areal relations. The trough was pinched out and strongly deformed and eroded by post-Miocene diastrophism. Its strata were steeply tilted, locally overturned and overthrust, and in places largely removed. Thrusts, erosion, slides, and alluvial debris have obliterated or hidden stretches near its mouth, both heads, and intermittently between these points. Evidence secured in Caliente Range and environs, in combination with state-wide data, suggests the following history. In the lower Oligocene California seems to have been completely emergent, with continental deposits being locally laid down near the present coast. In the upper Oligocene the sea invaded the state as a narrow inlet occupying the newly initiated Caliente trough, continental deposition continuing in most former areas of that nature. The marine Miocene of California is a transgressive series, essentially conformable basinward, but revealing, strandward, the occurrence of two oscillations which respectively inaugurate and divide its upper third. It comprises three End_Page 193------------------------------ nearly equal major natural divisions, the Vaqueros, Temblor, and Monterey stages, which approximate lower, middle, and upper Miocene. Each of these has a more or less distinctive epeirogenic history, fauna, and average physical aspect. The sea transgressed throughout the Vaqueros stage, hesitated without receding, and then advanced more widely during the Temblor. Moderate regression accompanying diastrophism of locally prominent to locally imperceptible intensity and a widespread quickening of vulcanism then caused strandward unconformity. In early lower Monterey (Briones) time the sea again advanced widely. Its boundaries remained more or less static during the late lower Monterey (Cierbo). Moderate regression and diastrophism then again caused strandward unconformity. In upper Monterey (Neroly) time the sea once more advanced, reaching its widest extent during the epoch. The Miocene series records progressively cooler waters, the tropical Vaqueros fauna giving way to the subtropical fauna of the Temblor, and this n turn to the slightly hardier fauna of the Monterey. Each fauna changed relatively slowly during its stage, with hardier forms of the succeeding dynasty encroaching as an admixture in open, cooler waters, and then gave way to a new fauna with relative rapidity during a short transitional interval corresponding to one of the epeirogenic movements that divide the Miocene series of California into approximately equal thirds as regards major physical and coincident faunal units. Wide regression resulting in almost or quite complete emergence of California separates the Miocene series from the markedly different and more restricted Pliocene series.

Parameters measured by well logs define rock properties and seismic reflections at lithology interfaces. Parameters from standard embedding claystones are normally used when calculating the top sand amplitude variation with offset (AVO) response, but this might give erroneous results when the real claystone rock properties deviate from the standard. Using cuttings and high-quality wireline logs from well 34/8-A-33 H above the Visund field in the northern North Sea, we evaluated rock properties of the Pleistocene glaciomarine claystones, Lower Miocene and Upper Oligocene oozy claystones, Lower Oligocene and Eocene smectite-rich claystones, and two interbedded sands. Glaciomarine claystones fit best with the Greenberg-Castagna equation and have the highest measured velocities even though they are the shallowest buried sediments. Environmental scanning electron microscope analysis proves the Lower Miocene and Upper Oligocene claystones to be oozy. The amount of low-density oozy material causes significant shifts in the log curves and makes the ooze-rich claystones plot far off the trend given by the Greenberg-Castagna equation. We, therefore, developed a new equation for S-wave velocity prediction for ooze-rich claystones with average densities between 1.7 and 1.85 g/cm3. The VP/VS ratios increase with depth in the Lower Oligocene and Eocene claystones of the Hordaland Group, and we interpreted this to reflect a downward increase in the amount of smectite, which existence was proven by X-ray diffraction analysis. We modeled how the seismic response at the top of a sand changes with embedding claystone type, saturation fluid, and offset. In glaciomarine claystones, the top of a brine-saturated sand corresponds to a negative trough reflection, in ooze-rich claystones to a positive peak reflection, and in smectite-rich claystones the reflection amplitude is close to zero. The predicted AVO response of sands in oozy claystones is highly dependent on whether the measured or calculated S-wave velocity has been used in the modeling.