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P. Cloud

Publications and source records attributed to P. Cloud.

5 recordsLinked to original sources

Calcite-impregnated defluidization structures in littoral sands of Mono Lake, California

Associated locally with well-known tufa mounds and towers of Mono Lake, California, are subvertical, concretionary sand structures through which fresh calcium-containing artesian waters moved up to sites of calcium carbonate precipitation beneath and adjacent to the lake. The structures include closely spaced calcite-impregnated columns, tubes, and other configurations with subcylindrical to bizarre cross sections and predominantly vertical orientation in coarse, barely coherent pumice sands along the south shore of the lake. Many structures terminate upward in extensive calcareous layers of caliche and tufa. Locally they enter the bases of tufa mounds and towers. A common form superficially resembles root casts and animal burrows except that branching is mostly up instead of down. Similar defluidization structures in ancient sedimentary rocks have been mistakenly interpreted as fossil burrows.

California

Earliest Phanerozoic or latest Proterozoic fossils from the Arabian Shield

We report here the first biologically definable fossils from pre-Saq (pre-Middle Cambrian) rocks of the Arabian Shield. They include the distinctive helically coiled tubular filaments of the oscillatorialean blue-green alga Obruchevella parva as well as two size classes of spheroidal unicells of uncertain affinity. Also present is the conical stromatolite Conophyton and unidentified stromatolites. All occur in cherty limestones of the Jubaylah Group, northern Saudi Arabia, a nonmarine to locally marine taphrogeosynclinal sequence that fills depressions along the northwest-trending Najd faults. Conophyton has heretofore been found only in strata older than about 680 Ma (except for puzzling records in modern hot springs) while Obruchevella is so far known only from rocks between about 680 and 470 Ma old. Thus it appears that the Jubaylah Group is close to the Proterozoic-Phanerozoic transition. The simple spheroidal nanno-fossils are not diagnostic as to age. Their relationships within what appears to be early diagenetic chert suggest a classical algal-mat association. The brecciated and microchanneled appearance of much of the fossiliferous rock, its locally dolomitic nature, and the prevalence of cryptalgalaminate favors a very shallow, locally turbulent, and perhaps episodically exposed marine or marginal marine setting. The Jubaylah Group lies unconformably beneath the Siq Sandstone (basal member of the Saq Sandstone) of medial Cambrian age, rests nonconformably on crystalline basement, and has yielded a K-Ar whole-rock age (on andesitic basalt) of ∼540 Ma. To judge from the fossils, however, that age may be as much as 100 Ma or more too young.

Arabian Shield

On microbial contaminants, micropseudofossils, and the oldest records of life

Microbial contaminants may be introduced on outcrop as well as en route to or in the laboratory. Micropseudofossils may be natural or man-made. It is possible to recognize such misleading objects and important that they are not allowed to dilute the growing record of authentic pre-Phanerozoic life. Filamentous microbial contaminants from minute cracks in samples of ancient carbonate rocks from Brazil (perhaps 1 Ga old) and South Africa (∼2.3 Ga old) are similar to occurrences previously described as fossils. Published records of supposedly Archean microbial life also include microcontaminants and laboratory artifacts. Although microstructures from sedimentary rocks of the Swaziland system could be fossils, they are not demonstrably so. The oldest structurally preserved fossils yet known seem to be the filaments described by Lois Nagy from stromatolitic limestone in the ∼2.3 Ga old Malmani Dolomite of South Africa. It will be difficult to establish unequivocal older records in the absence of definitive ultrastructural or micro-chemical evidence.

Precambrian Research

Entropy, materials, and posterity

Materials and energy are the interdependent feedstocks of economic systems, and thermodynamics is their moderator. It costs energy to transform the dispersed minerals of Earth's crust into ordered materials and structures. And it costs materials to collect and focus the energy to perform work - be it from solar, fossil fuel, nuclear, or other sources. The greater the dispersal of minerals sought, the more energy is required to collect them into ordered states. But available energy can be used once only. And the ordered materials of industrial economies become disordered with time. They may be partially reordered and recycled, but only at further costs in energy. Available energy everywhere degrades to bound states and order to disorder - for though entropy may be juggled it always increases. Yet industry is utterly dependent on low entropy states of matter and energy, while decreasing grades of ore require ever higher inputs of energy to convert them to metals, with ever increasing growth both of entropy and environmental hazard. Except as we may prize a thing for its intrinsic qualities - beauty, leisure, love, or gold - low-entropy is the only thing of real value. It is worth whatever the market will bear, and it becomes more valuable as entropy increases. It would be foolish of suppliers to sell it more cheaply or in larger amounts than their own enjoyment of life requires, whatever form it may take. For this reason, and because of physical constraints on the availability of all low-entropy states, the recent energy crises is only the first of a sequence of crises to be expected in energy and materials as long as current trends continue. The apportioning of low-entropy states in a modern industrial society is achieved more or less according to the theory of competitive markets. But the rational powers of this theory suffer as the world grows increasingly polarized into rich, over-industrialized nations with diminishing resource bases and poor, supplier nations with little industry. The theory also discounts posterity, the more so as population density and percapita rates of consumption continue to grow. A new social, economic, and ecologic norm that leads to population control, conservation, and an apportionment of low-entropy states across the generations is needed to assure to posterity the options that properly belong to it as an important but voiceless constituency of the collectivity we call mankind. ?? 1977 Ferdinand Enke Verlag Stuttgart.

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