Miocene Stratigraphy Research Articles

Lower Miocene Stratigraphy and Petroleum Potential, Offshore Galveston and Jefferson Counties, Texas: ABSTRACT

Lower Miocene sediments in the southeast Texas coastal area can be divided into 2 distinct trends. The basal Miocene interval from the top of the Oligocene Discorbis upward to the Robulus chambersi is a predominantly regressive-marine sequence that reflects the gradual progradation of Miocene sands into this area. The overlying sequence from Robulus chambersi to Amphistegina (B) consists of deltaic and delta-related sediments that reflect continued marine regression and seaward progradation of a large early Miocene delta system. In the nearshore Galveston and High Island areas, the basal Miocene interval contains a series of potential reservoir sandstones, most of which are above the abnormally pressured zones and occur at depths of less than 9,500 ft. Farther offshore, the younger Amphistegina (B) sandstones become favorable exploration objectives. Several lower Miocene biostratigraphic zones are identifiable throughout the area and an attempt has been made to relate each zone to particular lithologic conditions or depositional environments. Because of the general southward movement of the shoreline during the Miocene and a relatively limited supply of sand, prospective Miocene sandstone trends in the southeast Texas offshore occur in narrow belts approximately parallel with the present coastline. Identification of these favorable trends is essential to a successful exploration program in this area. End_of_Article - Last_Page 1695------------

Miocene Stratigraphy and Age Determinations, Rusinga Island, Kenya

Potassium–argon dating of the lavas of Rusinga Island, and a re-investigation of the associated sediments, indicate that most of the vertebrate fossils and nearly all of the early hominoids have come from strata about 18 million years old.

Oligocene and Lower Miocene Stratigraphy of Western and Northeastern Falcon Basin, Venezuela

The Falcon Basin is in northwestern Venezuela. It formed during the late Eocene or Oligocene. During the Oligocene and early Miocene, this small, narrow, east-west trending trough covered the greater part of Falcon State and adjoining parts of Zulia, Lara, and Yaracuy. After the early Miocene, the trough disappeared, and deposition was mainly confined to northern and eastern Falcon. The first deposits in the Falcon Basin were upper Eocene conglomerates, overlain by marine shales. In the central part of the basin, Oligocene rocks lie concordantly on these shales. Toward the basin margins, the Oligocene overlaps them and rests on older Eocene beds with angular unconformity. The Oligocene to Oligo-Miocene rocks in the basin are a complex of facies deposited during a marine transgression. In most of central Falcon, this complex is represented by relatively deep-water facies. In ascending order, the section there consists of: a sandstone and shale unit, a shale, and a shale with thin limestones and sandstones interbedded. The total thickness of this section exceeds 2,000 meters in some areas. The central-basin Oligocene to Oligo-Miocene section grades to shallower-water facies toward the basin margins. These facies include: reef limestones, and backreef limestones, shales, and black chert-bearing sandstones and conglomerates near the north-central margin; thick-bedded sandstones and interbedded clays near the western margin; limestones, sandstones, and shales near the south-central margin; shales and black chert-bearing conglomerates and sandstones near the southeastern margin. In most of the basin, the Oligocene to Oligo-Miocene facies-complex is topped by a lower Miocene shale unit. Toward the basin edges, the lower part of this unit grades into the top of the underlying facies-complex. At its thickest, this shale exceeds 2,000 meters. Above it in most of the basin, lies a series of lower Miocene sandstones, siltstones, and shales. Two isopach maps included in the paper show that the Falcon Basin was an east-northeast-trending trough. It was divided into two sub-basins, one in eastern and one in western Falcon. These were separated by an area where the basin was narrower and the section thinner. Three facies maps are also included. They show that (1) mostly shales were deposited in the deeper areas of the basin during Oligocene and early Miocene time, and (2) the shales grade laterally to interbedded reefal limestones, sandstones, conglomerates, and shales near the basin rim.

The Miocene Stratigraphy of the Fuji River Valley, Central Japan

The Miocene Stratigraphy of the Fuji River Valley, Central Japan

Die Bedeutung des Aufschlusses von Maade bei Esbjerg für die Gliederung des Obermiozäns

Die Bedeutung des Aufschlusses von Maade bei Esbjerg für die Gliederung des Obermiozäns

Miocene Stratigraphy of Siogama District, Miyagi Prefecture

In this paper the stratum that is seen in the Shiogama District is divided into three parts; the Shiogama, the Hamada, and the Matsushima formations., There was found Desmoslylus in the upper part of the Hamada formation., The writers intended to determine the age of the formations by studying the fossils found there, and presumed them to l e of middle Miocene.,

Types of Californian Micoene Foraminifera

FOLLOWING upon the review by “A.M.D.” of Dr. R. M. Kleinpell's monograph on “Miocene Stratigraphy of California” in NATURE of December 23, 1939, p. 1030, it may be of interest to note that the topotype material with the actual described types referred to by the author of the above work have now been deposited by me in the micropalaeontological collection of the Stanford University.

Miocene Stratigraphy of California

Miocene Stratigraphy of California

Miocene stratigraphy of the easternmost Ventura Basin, California, a preliminary statement

<h3>Background</h3> Poor vessel wall apposition of flow diverter (FD) stents poses risks for stroke-related complications when treating intracranial aneurysms, necessitating long-term surveillance imaging. To facilitate quantitative evaluation of deployed devices, a novel algorithm is presented that generates intuitive two-dimensional representations of wall apposition from either high-resolution contrast-enhanced cone-beam CT (VasoCT) or intravascular optical coherence tomography (OCT) images. <h3>Methods</h3> VasoCT and OCT images were obtained after FD implant (n=8 aneurysms) in an experimental sidewall aneurysm model in canines. Surface models of the vessel wall and FD device were extracted, and the distance between them was presented on a two-dimensional flattened map. Maps and cross-sections at potential locations of malapposition detected on VasoCT-based maps were compared. The performance of OCT-based apposition detection was evaluated on manually labeled cross-sections using logistic regression against a thresholded (≥0.25 mm) apposition measure. <h3>Results</h3> VasoCT and OCT acquisitions yielded similar Grading of Regional Apposition after Flow-Diverter Treatment (GRAFT) apposition maps. GRAFT maps from VasoCT highlighted 16 potential locations of malapposition, of which two were found to represent malapposed device struts. Logistic regression showed that OCT could detect malapposition with a sensitivity of 98% and a specificity of 81%. <h3>Conclusions</h3> GRAFT delivered quantitative and visually convenient representations of potential FD malapposition and occasional acute thrombus formation. A powerful combination for future neuroendovascular applications is foreseen with the superior resolution delivered by intravascular OCT.

Miocene Stratigraphy of California. Robert M. Kleinpell

<i>Miocene Stratigraphy of California</i>. Robert M. Kleinpell

Miocene Stratigraphy and Paleontology of Palos Verdes Hills, California

The Miocene of the Palos Verdes Hills embraces a thickness of about 2,500 feet of rocks here designated as Monterey shale, and the base is not exposed in the region where the oldest beds crop out. Five main lithologic units are recognized, consisting, in ascending order, principally of silty shale, porcelaneous and cherty shale, phosphatic shale, diatomite, and radiolarian mudstone. Three local members are named and mapped, the lowest one of which includes three of the main lithologic units and also two named tuff beds. Foraminifera are found in all the main units and are assigned to nine faunal zones indicating a time range extending from early Middle Miocene to the top of the Upper Miocene, as these terms are generally used in Coast Range chronology. These beds overlap orthward onto a schist basement of Franciscan (?) rocks, and this northward overlap apparently continues to the Torrance and Playa del Rey oil fields in the southern part of the adjoining Los Angeles Basin. Mollusks from detrital rocks at the base of the overlapping beds on the north slope of the hills represent a fauna that in many respects is a new one for the Coast Ranges, as it includes a number of tropical genera not heretofore recorded there.