The Claypool Site: A Cody Complex Site in Northeastern Colorado

1960 ◽  
Vol 26 (2) ◽  
pp. 223-235 ◽  
Author(s):  
Herbert W. Dick ◽  
Bert Mountain
Keyword(s):  
Geological Age ◽  
Sand Deposit ◽  
Cody Complex

AbstractEden and Scottsbluff points and Cody knives were found in situ in a sand deposit with an estimated geological age of 10,000 to 7000 years. Numerous other Cody complex artifacts from the surface of the site are described. Fragmentary remains of a mammoth in a marl bed are stratigraphically older than the Cody artifacts.

I.—The Geological Age of the Carrara Marbles

1915 ◽  
Vol 2 (7) ◽  
pp. 289-294
Author(s):  
T. G. Bonney ◽  
H. H. Winwood
Keyword(s):  
Mountain Regions ◽  
Geological Age ◽  
The Subject

The statuary marbles of Carrara have been repeatedly asserted to be metamorphic limestones of earlier Mesozoic or later Palæozoic age. Similar statements were once frequent in regard to other mountain regions, but they have one by one dropped out of geological literature. This, however, is such a hardy perennial as to be still repeated in petrological and other textbooks. Doubts, however, were felt by the first author in 1878, and these became almost certainties after 1886, but as each visit was only for a few hours, and did not allow of a proper examination of the rocks in situ, he deferred writing on the subject till he could spend a longer time at Carrara. That opportunity, however, never came, and is not now likely to occur ; but on finding not long since that his friends, Professor Boyd Dawkins and the Rev. H. H. Winwood, had visited the quarries in 1898, and the latter had published an account of the district, with a sketch-section drawn by the former, he communicated with them, and the following paper summarizes the experience of the three, which it is hoped may help in laying another metamorphic ghost.

Geological Age of the Claypool Site, Northeastern Colorado

1960 ◽  
Vol 26 (2) ◽  
pp. 236-243 ◽  
Author(s):  
Harold E. Malde
Keyword(s):  
Climatic Changes ◽  
Coarse Sand ◽  
Physical Characteristics ◽  
Washington County ◽  
Brown Soil ◽  
Geological Age ◽  
Thermal Maximum ◽  
Cody Complex ◽  
Fine Gravel ◽  
Eolian Deposit

AbstractArtifacts related to the Cody complex occur in medium-grained sand that is spread as a blanket eolian deposit a few feet thick in the Claypool site area, Washington County, Colorado. The artifact-bearing sand lacks noticeable dunal topography and lies unconformably on marl of Yarmouth age and on waterlaid coarse sand and fine gravel of Kansan age that underlie the marl. The deposits underlying the artifact-bearing sand are much too old to date the artifacts precisely, but the physical characteristics of the artifact-bearing sand suggest that it was deposited under conditions cool and dry, rather than warm and dry, possibly during retreat of Valders ice that began about 10,000 years ago. A moderately mature Brown Soil about 5 feet thick developed on the sand, possibly about 7000 to 5000 years ago during a moist phase of the Thermal Maximum. Thus, the artifacts are possibly 10,000 to 7000 years old. Deposits which overlie the artifact-bearing sand reflect several episodes of erosion and sedimentation that are inferred to represent climatic changes.

Some new ichnospecies stored in the Geological Department of the National Museum of Natural History, NAS of Ukraine

Geo&Bio ◽  
2021 ◽  
Vol 2021 (20) ◽  
pp. 9-26
Author(s):  
Volodymyr Grytsenko ◽  
Keyword(s):  
Oil And Gas ◽  
Sedentary Lifestyle ◽  
Soft Soil ◽  
National Museum ◽  
Geological History ◽  
Oil And Gas Fields ◽  
Geological Age ◽  
Geological Past ◽  
Gas Fields

During the last decades, many scientists worldwide have focused on the study of activity signs of animals. Such signs of various animals have appeared in the geological history since Ediacaran rocks and can be found until today. They can be signs of sedentary lifestyle or tracks of moving of animals (both vertebrates and invertebrates), evidence of birth (e.g., eggshell fragments), sliding traces of molluscs and other organisms. In some cases, the study of ichnofossils is of great importance, especially for the so-called "palaeontologically dumb" sequences. However, the identification of the nature of ichnofossils is an issue. Sometimes, particular kinds of animals can be identified based on the shape and trajectory of traces. But usually such identifications are impossible, therefore an artificial nomenclature is used for these ichnospecies. In particular cases, ichnofossils help to resolve the problem of identification of ancient facies. It is often impossible to identify their position in the biological system, but the behaviour of animals can be clarified. Different animals leave imprints of their traces and tracks depending on the specifics of facies in the bottom of the sea or on the surface of the ground nearby to continental waterbodies. These can be traces of invertebrate and vertebrate animals. Soft soil is the most favourable for the formation of traces, although specific conditions are required for the preservation of these traces. There are organisms that leave signs of drilling on the solid bottom and on rocks. In the results, we can obtain some information, but only a part of it allows to obtain correct identifications. It is often impossible to identify animals according to their traces. Ichnofossils from deposits of various age and facies are studied by specialists in all continents and in the seabed. Ichnology, a new scientific branch emerged that develops rapidly. Ichnological approaches allow to identify ecological (facies) conditions of the geological past and are used in searches for oil and gas fields. The disadvantages of ichnology are the ambiguous interpretation of ichnospecies and the use of the same name for different objects (synonyms). In this paper, some new ichnospecies of various geological age are identified and described along with images of traces of unknown animals in situ.

VIII.—Burning Cliffs of the Banks of the Mackenzie River, etc

1908 ◽  
Vol 5 (12) ◽  
pp. 562-563
Author(s):  
H. W.
Keyword(s):  
Spontaneous Combustion ◽  
The Arctic ◽  
Carbonaceous Matter ◽  
Geological Age ◽  
Arctic Sea ◽  
Rupert's Land ◽  
Mackenzie River

As bearing upon the phenomenon of the spontaneous combustion of bituminous beds of coaly or carbonaceous matter of any geological age (charged with pyrites) in sitû, the account given by Sir John Richardson, C.B., F.R.S., in his “Arctic Searching Expedition; a Journal of a Boat-voyage through Rupert's Land and the Arctic Sea,” 1851, vol. i, may not be without interest in this connection.

Geological age by instrumental analysis: the 29th Hallimond Lecture

1999 ◽  
Vol 63 (3) ◽  
pp. 297-311 ◽  
Author(s):  
W. Compston
Keyword(s):  
Laser Ablation ◽  
Spatial Resolution ◽  
Analytical Method ◽  
Bimodal Distribution ◽  
Instrumental Analysis ◽  
Hole Depth ◽  
Future Developments ◽  
Geological Age ◽  
Age Determinations

AbstractThe need in geology for in situ U-Pb age determinations of minerals is illustrated by two examples: the internal age dispersion developed within the zircon SL13 shortly after original crystallization, and the occurrence within minerals of old cores and later overgrowths. SL13 contains rare μm-sized patches of unsupported radiogenic Pb and a mainly bimodal distribution of 206Pb/238U ages otherwise. Both observations are consistent with original crystallization at 580 Ma and Pb loss at 565 Ma. Age precision is controlled by the ions counted for radiogenic Pb, and varies with instrumental sensitivity, age and U contents of the target. Laser-ablation ICPMS has similar spatial resolution and sensitivity to SIMS but consumes more sample because of much greater hole-depth in practice. Like SIMS, the measured Pb+/U+ is biased and also changes with depth so comparison with a standard mineral is necessary. Analyses of reference zircons reported here indicate that the reproducibility of Pb/U ages by ICPMS is limited by residual bias, not ion counting errors. For multipurpose ICPMS at least, the Hg background at mass 204 prohibits the measurement of 204Pb for common Pb estimation. A third micro-analytical method, ‘CHIME’, and future developments in SIMS and ICPMS are discussed briefly.

Recovery and Reconstruction of A.L. 444-2

2004 ◽  
Author(s):  
William H. Kimbel ◽  
Yoel Rak ◽  
Donald C. Johanson ◽  
Ralph L. Holloway ◽  
Michael S. Yuan
Keyword(s):  
Laser Fusion ◽  
Geological Age ◽  
Crystal Laser ◽  
Occlusal Wear ◽  
The Matrix ◽  
The Face ◽  
Temporal Bones ◽  
The Hill ◽  
Eastern Edge

The A.L. 444-2 skull was found on 26 February 1992, during a strategic paleontological survey of Kada Hadar Member sediments that are stratigraphically situated between BKT-1 and BKT-2 tephras, on the eastern edge of the Awash River’s Kada Hadar tributary. Yoel Rak discovered two fragments of hominin occipital bone (A.L. 444-1) at the base of a steep hill composed of Kada Hadar Member silts and clays capped by a weathered sandstone remnant. Subsequent examination of the upslope surface revealed additional hominin skull fragments (the temporal bones and maxillae) clustered together and partially exposed in a narrow gully that dissected the face of the hill. During the next seven days, probing and dry sieving of the gully infill and hillside colluvium over a 77 m2 area led to the recovery of fragments representing about 75%–80% of a single hominin skull. It was immediately apparent that the upslope finds duplicated the anatomical parts represented by the two A.L. 444-1 occipital fragments and therefore constituted a second hominin individual, cataloged as A.L. 444-2. In addition, the lambdoidal suture of the A.L. 444-1 occipital is completely unfused, suggesting subadult status, whereas fused cranial sutures and extreme dental occlusal wear indicate an advanced ontogenetic age for A.L. 444-2. In February–March 1993 the A.L. 444 hillside was excavated in an effort to locate missing parts of the A.L. 444-2 skull and to determine its precise stratigraphic provenance. No further remains of the hominin skull were encountered in situ, but a complete viverrid cranium and indeterminate fragments of large mammal bone with preservation and patina (mottled dark gray, white, and yellowish gray) identical to those of the hominin were excavated in an unstratified, cemented carbonate silt that exactly matches the matrix adhering to A.L. 444-2. We are confident that the hominin skull is from this sedimentary horizon. It is approximately 10.5 m stratigraphically below the BKT-2 tephra, which outcrops in the immediate vicinity of A.L. 444 Single-crystal laser fusion (SCLF) 40Ar/39Ar ages for BKT-2 and Kada Hadar Tuff (KHT) bracket the geological age of A.L. 444-2 between 2.94 and 3.18 Myr (Kimbel et al., 1994; Walter, 1994; Semaw et al., 1997).

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

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