Submarine Rocks Research Articles

40Ar [sbnd]39Ar stepwise degassing experiments on some submarine rocks

40Ar 39Ar stepwise degassing experiments were made on six submarine rocks. The 40Ar 39Ar ages thus obtained were compared with the conventional K-Ar ages. Samples with high K-content generally give a linear correlation on a ( 40Ar*/ 36Ar*) - ( 39Ar*/ 36Ar*) diagram, showing insignificant excess 40Ar. The excess 40Ar is shown to reside in higher temperature fractions, though the amount is small (< 10 −11 mol/g) and becomes significant only for low K-content samples. Basalt drilled from the Experimental Mohole gives a 40Ar 39Ar age of 19 my which agrees with magnetic anomaly lineation isochron. The K-Ar age of 42 my reported for this sample by Kulp is shown to be in error owing to excess 40Ar. The geophysical implications of the 40Ar 39Ar ages of other samples are also discussed.

Evidence of subsidence of seamounts in the north-western Pacific

The subsidence of seamounts in the northwestern Pacific is suggested from the unexpected high vesicularity of submarine basaltic rocks which were dredged from great depths. There exists a tendency that the closer the seamount is situated to the trench axis, the greater the amount of subsidence becomes.

Marine Diagenesis of Carbonate Sediment, Bonaire, Netherlands Antilles

ABSTRACT A discontinuous layer of lithified carbonate sand underlies a small portion of the Lac, a large lagoon on the southeastern coast of Bonaire. The layer lies thirty-five centimeters below the sediment surface, varies from five to twenty centimeters in thickness and is restricted to an area beneath a broad intertidal and subtidal flat. Beachrock crops out in the high intertidal zone. The lithified layer consists of grainstone cemented by acicular aragonite. Numerous lines of evidence indicate the cementation occurred in the marine environment. The lithified layer is at present continuously saturated with normal sea water. Evidence for earlier dissolution or erosion is lacking. The submarine cemented rocks lack the gray algal coating which is characteristic of beachrock and subaerially exposed coral rubble. Carbon 14 dating of the rock indicates cementation less than 900 years B.P. Study of the constituent particles of the lithified layer and the sediment above and below indicates continuous marine sedimentation. Four distinct types of micrite are present in the beachrock and submarine cemented layer: 1) structureless aragonite which fills or partially fills intraparticle pore space, 2) aragonite with a pellet-like fabric which fills or partially fills interparticle pore space, 3) aragonite coatings on single skeletal fragments with a gradational boundary between the fragment and coating and 4) high- and low-magnesium calcite which coats single and multiple skeletal fragments with, a sharp contact between the grain and micrite. This latter type is the most common form of micrite and might easily be misinterpreted as a cement. However, it can be shown that it results from micritization of encrusting coralline algae. The coralline algal encrustation was high-magnesium calcite. Electron microprob and X-ray diffraction analysis of these coatings demonstrated that as micritization proceeds and the microstructure of the algal coating is destroyed the mineralogy changes from high- to low-magnesium calcite.

Characteristic thermomagnetic curve in submarine basalts

Thermomagnetic analyses at H=3,000 oe were carried out for 24 submarine rocks dredged from 10 sites mostly from seamounts in the Pacific Ocean. Most of the samples, which are believed to be in situ, show an irreversible increase of both Js and Curie temperature on heating both in air and in vacuum. This increase is explained as unmixing of the original titanomaghemite to magnetite and Ti-rich phases such as hemo-ilmenite and/or pseudo-brookite. The characteristic irreversible change in the thermomagnetic curve is almost sufficient to discriminate uniquely submarine basalts, erupted and preserved in the sea, from those erupted in air.

K-Ar ages of seamounts along the Japan Trench and the effect of acid leaching on the K-Ar age of a dredged submarine rock

The ages of, submarine rocks dredged from seamounts along the Japan Trench were determined by K-Ar method. In order to obtain more reliable age, the effect of acid leaching on an altered submarine rock was examined. Some samples treated by acid solution gave K-Ar ages up to 20% older than the original untreated sample. This result suggests a possibility that, if suitable acid teratment conditions are found, they would result in more reliable ages for submarine rocks. Some submarine rocks dredged from seamounts along the Japan Trench on the oceanic side gave K-Ar ages of about 70-80 m.y, whereas a sample dredged from a seamount on the Japanese Islands side gave a substantially younger age. Considering the present result as well as previous data, the last volcanic activity along the Japan Trench seems to have occurred about 70-80 m.y ago or older.

45. K-Ar ages of dredged submarine rocks(Abstracts of Papers submitted for the Meetings of the Society)

45. K-Ar ages of dredged submarine rocks(Abstracts of Papers submitted for the Meetings of the Society)

38. On the reliability of K-Ar Ages of dredged submarine rocks(Abstracts of Papers submitted for the Meetings of the Society)

38. On the reliability of K-Ar Ages of dredged submarine rocks(Abstracts of Papers submitted for the Meetings of the Society)

Geophysics: Dating Submarine Rock

Geophysics: Dating Submarine Rock

Breccia and Pennsylvanian cave filling in Mississippian Saint Louis Limestone, Putnam County, Indiana

ABSTRACT A limestone breccia and several bodies of shale and sandstone in Mississippian St. Louis Limestone were discovered in a quarry opened during the summer of 1959 in the SE NW sec. 15, T. 15 N., R. 4 W., Putnam County, Indiana. A small mass of sandy limestone conglomerate overlay part of the breccia. Nearly all these bodies have been removed in quarrying. The breccia and the shale-sandstone masses appear to have originated from two separate geologic processes which occurred at two different times. The origin of the breccia is in doubt because not enough critical evidence is available to prove conclusively any single origin. The authors believe, however, that the breccia probably is the product of a submarine rock slump during St. Louis time which was triggered by the tectonic activity that initiated early movements along the Mt. Carmel Fault. Other possible origins, such as solution of evaporites accompanied by collapse of overlying rock or formation of caves in a karst terrain followed by roof collapse, are not supported by the evidence observed. The shale-sandstone bodies are believed to be rocks of Pennsylvanian age which were deposited in caverns developed during the Mississippian-Pennsylvanian erosion interval. The limestone conglomerate probably is of the same age as the shale-sandstone bodies.

Locating Seaweeds and Artificial Submarine Rocks with the Supersonic Fish Finder

Locating Seaweeds and Artificial Submarine Rocks with the Supersonic Fish Finder

Erratum to : Locating Seaweeds and Artificial Submarine Rocks with the Supersonic Fish Finder

Erratum to : Locating Seaweeds and Artificial Submarine Rocks with the Supersonic Fish Finder

PHYSIOLOGICAL STUDIES OF GELIDIUM CARTILAGINEUM. I. PHOTOSYNTHESIS, WITH SPECIAL REFERENCE TO THE CARBON DIOXIDE FACTOR

GELIDIUM CARTILAGINEUM is a red alga with repeatedly pinnately branched, maroon-purple fronds. In southern California it is represented by the variety robustum, which grows most abundantly on submarine rocks 10 to 40 or more feet below sea level, and which may reach a length of 4 feet. This plant is the principal agarophyte for the manufacture of agar on the Pacific coast of North America. Agar shortage in the last few years has stimulated considerable interest in the study of agarophytes. The importance of raw materials in an industry cannot be over emphasized. The success of the American agar industry will depend, in large measure, on the adequacy of the supply of agarophytes. A knowledge of their physiology and ecology is prerequisite to finding ways of insuring an adequate natural supply of these seaweeds, or, if necessary, of cultivating them on a commercial scale. A program of research on agarophytes has therefore been inaugurated at the Scripps Institution of Oceanography. The present report, the first of a series, is concerned with the photosynthetic activities of this Gelidium. Photosynthesis is the fundamental process providing both energy and substance for the synthesis of the whole plant organism. It follows that in studies of photosynthesis are to be found solutions to many problems concerning the ecological behavior of plants. It is therefore the object of the authors to study the photosynthetic activity of Gelidium cartilagineum under different environmental conditions, and especially to determine the effect of varying light, temperature, and carbon dioxide concentration in sea water, in order to obtain some idea of the optimum conditions for the growth of this particular plant. THE CARBON DIOXIDE FACTOR.-Since photosynthesis is a process requiring carbon dioxide as a substrate, the rate of photosynthesis cannot be constant over a period of time unless carbon dioxide is supplied at a constant rate, or enough is continually present to saturate the enzyme system involved. It has been well established that carbon dioxide is a limiting factor in the photosynthesis of land plants during the day, since the photosynthetic activitv of leaves is greatly enhanced by increasing the carbon dioxide concentration in the air. In the case of algae and aquatic plants under natural conditions, e.g., filamentous algae and phytoplankton in particular,

Closure on Submarine Rock Excavation

Closure on Submarine Rock Excavation