Pleistocene Volcanic Rocks Research Articles

Limestones and Red Soils of Bermuda

Research Article| August 01, 1969 Limestones and Red Soils of Bermuda G BLACKBURN; G BLACKBURN Commonwealth Scientific and Industrial Research Organization, Division of Soils, Adelaide, Australia Search for other works by this author on: GSW Google Scholar R. M TAYLOR R. M TAYLOR Commonwealth Scientific and Industrial Research Organization, Division of Soils, Adelaide, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information G BLACKBURN Commonwealth Scientific and Industrial Research Organization, Division of Soils, Adelaide, Australia R. M TAYLOR Commonwealth Scientific and Industrial Research Organization, Division of Soils, Adelaide, Australia Publisher: Geological Society of America Received: 23 Dec 1968 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1969, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1969) 80 (8): 1595–1598. https://doi.org/10.1130/0016-7606(1969)80[1595:LARSOB]2.0.CO;2 Article history Received: 23 Dec 1968 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation G BLACKBURN, R. M TAYLOR; Limestones and Red Soils of Bermuda. GSA Bulletin 1969;; 80 (8): 1595–1598. doi: https://doi.org/10.1130/0016-7606(1969)80[1595:LARSOB]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 Red clayey soils, which were found to be highly phosphatic, overlie relatively pure limestone in the northern part of Bermuda. X-ray diffraction of the 0.2 to 0.5 mm sand fractions of two such soils revealed a mineralogy similar to that of volcanic impurities in one outcrop of limestone, in beach sand, and in submarine red clay from Castle Harbour. The occurrence of the distinctive red soils on these islands appears to have depended on weathering of restricted deposits of limestone that contained significant proportions of minerals derived from Pleistocene volcanic rocks. These impure deposits overlaid the relatively pure limestone. The phosphate in the soil appears to have been derived from guano. 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.

A palaeomagnetic study of quaternary volcanic rocks from Turkey

A palaeomagnetic study has been carried out on the Pleistocene volcanic rocks of Turkey. The magnetic compass and sun compass orientation techniques were used in the collection of the samples. The use of the sun compass (or topographic sighting) is a necessary technique in the collection of volcanic rocks as indicated by the comparison of the results. The reliability of the NRM of the samples was tested by both alternating magnetic field and thermal demagnetization experiments. There was a good agreement between the results obtained from both techniques. However it was found that for some of the oxidized volcanic rocks the use of the thermal method could lead to an unrealistic result. The mean pole positions were found to be coincident with the axial dipole at 95% probability level for the Brunhes and Matuyama geomagnetic epochs. The between-lava dispersion parameters were used to estimate the magnitude of secular variation in these polarity epochs. Reflected light ore microscope and thermomagnetic analysis work was carried out on the material used in palaeomagnetic work. In general rocks were found to be unoxidized or slightly oxidized. It was difficult to set up a strict correlation between the stage of oxidation of the rocks and their polarity.

REVISION OF THE PLEISTOCENE STRATIGRAPHY IN KYUSHU FOR INTERPROVINCIAL CORRELATION

For the basis of interprovincial correlation the Pleistocene formations and volcanics in Kyushu were re-examined stratigraphically and the revised results are presented here. The following five areas were chosen for the stratigraphic revision; they are the Oita district, Nalcatsu district, southern half of Nagasaki Prefecture, marginal area of northern Kagoshima Bay, and the Miyazaki district. The Pleistocene formations and volcanic rocks are extensively developed in the above-mentioned areas and those in the respective areas serve as the standard section for a part of the Pleistocene stratigraphy. Consequently the systematic study on the geology in these areas gives a general outline of the stratigraphic correlation of the Pleistocene units in Kyushu. — Author.

Geology of the New Tanna Tunnel, Shin-Tok ai do Line

A new tunnel was excavated parallel to the old Tanna Tunnel from which it is removed for 50m to the north. The new tunnel passes through a thick section of older Miocene, Pliocene, and older Pleistocene volcanic rocks interbedded occasionally with thin layers of marine and lacustrine sediments. The Miocene Yugasima Group, Hudo Tunnel Basalt Group, Atami Tuffs, and Ohira Andesite Group were laid down under the sea, resulting in the prevalence of autobrecciated lava flows and water-quenched basaltic and andesitic glass breccias.The Pliocene arid Pleistocene volcanic rocks were largely accumulated subaerially, and therefore the lavas are frequently interbedded with unconsolidated ash layers. Many accidents and difficulties in the engineering proce sses were encountered during the excavation of the old tunnel.The study of the geology of the new tunnel revealed that these accidents and engineering difficulties arose where solfataric clay produced from the pyroclastic rocks and glass breccias of the Yugasima Group and also from the lava of the Pliocene Ainohara Andesite Group, fault breccias such as found in the Ohira Andesite Groupand also along the Tanna Fault cutting the pyroclastic rockes of the Pleistocene Taga Volcano at the center of the tunnel, and the unconsolidated ash layers are soaked with much underground water. During the excavation of the new tunnel, no great accidents nor engineering difficulties occ ur, largely owing to the fact that a great amount of the underground water is being drained by special tunnel which has been constructed along the old tunnel. It is emphasized that more detailed geological works than have done in the past, especially the observations on the mode of emplacement and deposition and also on the nature of alteration of volcanic materials, should be done before and during the engineering programs for any tunnels traversing volcanic rocks.

GEOMORPHOLOGY OF CIMA DOME, MOJAVE DESERT, CALIFORNIA

Cima Dome, a remarkably smooth symmetrical alluvium-fringed rock dome in the desert of southeastern California, is the prototype of Davis' granitic desert dome, supposedly convex and presumably developed by backwearing of a granitic fault block. Transit-stadia profiles across Cima Dome show concave or essentially straight slopes and demonstrate that it is not convex except to a slight degree in the uppermost 25 feet. Geophysical explorations by resistivity, gravity, and seismic methods on the southeastern flank reveal no boundary fault or any form unequivocably identifiable as the convex suballuvial bench deduced by Lawson. At its deepest point the granitic rock floor is buried by 1300 feet of overburden composed of 550 feet of alluvium, or geophysically comparable material, and 650 feet of more coherent rock, presumably welded rhyolitic tuff. Cima Dome is primarily a regraded part of an extensive late Pliocene-early Pleistocene erosion surface, Hewett's Ivanpah upland, now buried by Pleistocene volcanic rocks immediately to the west. The dome may be an erosion residual on that surface or it may have been created largely by subsequent deformation, primarily warping. Evidence cited favors the warping hypothesis. The present profile of Cima Dome is due to erosion and regrading in the current cycle, and in most places the smoothness of slope and the symmetry are due to uniform debris yielded by granular disintegration of homogeneous quartz monzonite composing the dome. The relations at Cima Dome and elsewhere suggest that the role of recent warping merits consideration with regard to the origin of closed basins, broad divides, disintegrated drainages, areas of dissection and related landscape features in the desert of southeastern California.