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1.
A comparison of paleobotanical records with archeological and ethnographic evidence from the Pacific Northwest shows a strong correlation between the expansion of Western red cedar (Thuja plicata) in coastal forests between 5000 and 2500 years ago and the evolution of a massive woodworking technology by native cultures. This suggests that an important component of cultural development was environmentally constrained until large cedar trees, the basic resource for canoe-building and plank-house construction, had become available in late Holocene time.  相似文献   

2.
A series of archeomagnetic measurements have been carried out on archeologic materials from Arizona and Mexico which can be compared with results from Europe and Asia. This comparison shows a westward drift of geomagnetic intensity at a rate of about 0.24 degree per year. Furthermore, an apparent coincidence between changes in the earth's magnetic moment and changes in the production rate of radiocarbon is observed.  相似文献   

3.
Doell RR  Cox A 《Science (New York, N.Y.)》1971,171(3968):248-254
We have considered several different types of records of long-period geomagnetic secular variation: direct measurements made in geomagnetic observatories; paleomagnetic measurements on Hawaiian lava flows with accurately known ages in the interval 0 to 200 years; paleomagentic measurements on Hawaiian lava flows with loosely determined ages within the interval 200 to 10,000 years ago; and worldwide paleomagnetic measurements of the average geomagnetic angular dispersion recorded in lava flows that formed during the past 0.7 million years. All these magnetic records indicate that, during this time, the nondipole component of the earth's field was lower in the central Pacific than elsewhere, as it is today. This, in turn, indicates that there is some type of inhomogeneity in the lower mantle which is coupled to the earth's core in such a way as to suppress the generation of the nondipole field beneath the central Pacific. With the present incomplete state of knowledge about the processes that give rise to the earth's field, it is uncertain whether undulations in the core-mantle interface or lateral variations in the composition and physical state of the lower mantle are ultimately responsible for the pattern of secular variation seen at the earth's surface.  相似文献   

4.
Geomagnetic Reversals during the Phanerozoic   总被引:1,自引:0,他引:1  
An antalysis of worldwide paleomagnetic measurements suggests a periodicity of 350 x 10(6) years in the polarity of the geomagnetic field. During the Mesozoic it is predominantly normal, whereas during the Upper Paleozoic it is predominantly reversed. Although geomagnetic reversals occur at different rates throughout the Phanerozoic, there appeaars to be no clear correlation between biological evolutionary rates and reversal frequency.  相似文献   

5.
It is suggested that the originally European species Littorina littorea was introduced to North Ameriea by Norse settlers about A.D. 1000. Its subfossil distribution might be used in tracing the extent of Norse travel in this region. Recent archeological finds match very well with the historical records of the Norse exploration and settlements. This activity seems to have been concentrated in Nova Scotia and Newfoundland.  相似文献   

6.
Archeological methodology and remote sensing   总被引:1,自引:0,他引:1  
We have shown that the different spectral surveying techniques and the resultant imagery vary in their applicability to archeological prediction and exploration, but their applications are far broader than we have indicated. Their full potential, to a considerable extent, still remains unexplored. Table 1 is a chart of the more common sensor systems useful to archeological investigators. Several kinds of photography, thermal infrared imagery, and radar imagery are listed. Checks in various categories of direct and indirect utility in archeological research indicate that the different systems do provide varying degrees of input for studies in these areas. Photography and multispectral photography have the broadest applications in this field. Standard black-and-white aerial photography generally serves the purposes of archeological exploration and site analysis better than infrared scanner imagery, radar, or color photography. However, the real value of remotesensing experimentation lies in the utilization of different instruments and in the comparison and correlation of their data output. It can be stated without doubt that there is no one all-purpose remotesensing device on which the archeologist can rely that will reveal all evidence of human occupations. Remote-sensing data will not replace the traditional ground-based site survey, but, used judiciously, data gathered from aerial reconnaissance can reveal many cultural features unsuspected from the ground. The spectral properties of sites distinguishable by various types of remote sensors may perhaps be one of their most characteristic features, and yet the meaning of the differential discrimnination of features has not been determined for the most part, since such spectral properties are poorly understood at this date. The difficulty in isolating the causes of acceptable definition in certain portion of the spectrum and the lack of acceptable definition in others suggests that the evaluation of remote-sensing devices discussed in this article is not always applicable to all environmental zones at all times and for all types of cultural features. The uncontrollable variables of terrain, ground cover, weather, types of archeological manifestations, and other factors all play an important role in the utility of the imagery to the archeologist. Factors within the control of the photographer or archeolgist, such as altitude, position of the sun, and the direction of flight, can greatly influence the utility of the sensor data. In addition, the variables should not be considered solely as they affect resolution. Resolution, per se, although an important photogrammetric parameter of remote-sensing imagery, is by no means the only important factor in data analysis. The synoptic overview, which is provided by aerial imagery, is frequently as necessary in interpretation as the spotting and identification of individual cultural features. Stated more simply, we might say: "To understand, one most certainly must see the forest as well as the individual trees." For maximum data retrieval, it is necessary that the archeologist attempt to utilize as many different types of remote-sensing devices under as many variable seasonal and climatic conditions as his resources and skill will allow. Only then he can select the most efficient system for the purpose in his area of study.  相似文献   

7.
Earthquake-induced liquefaction features in Holocene sediments provide evidence of strong prehistoric shaking, magnitude m(b) 6.2 to 6.7, in the Wabash Valley bordering Indiana and Illinois. The source of the one or more earthquakes responsible was almost certainly in or near the Wabash Valley. The largest event is interpreted to have occurred between 7500 and 1500 years ago on the basis of archeological, pedological, and stratigraphic relations.  相似文献   

8.
Recent numerical simulations have yielded the most efficient geodynamo, having the largest dipole intensity when reversal frequency is low. Reliable paleointensity data are limited but heretofore have suggested that reversal frequency and paleointensity are decoupled. We report data from 56 Thellier-Thellier experiments on plagioclase crystals separated from basalts of the Rajmahal Traps (113 to 116 million years old) of India that formed during the Cretaceous Normal Polarity Superchron. These data suggest a time-averaged paleomagnetic dipole moment of 12.5 +/- 1.4 x 10(22) amperes per square meter, three times greater than mean Cenozoic and Early Cretaceous-Late Jurassic dipole moments when geomagnetic reversals were frequent. This result supports a correlation between intervals of low reversal frequency and high geomagnetic field strength.  相似文献   

9.
Analytical techniques more usually applied in mineralogy have revealed consistent structural differences between the bones of wild and domestic animals from archeological deposits.  相似文献   

10.
本文设计了牧场、年度和公牛三因素的最小二乘固定模型和BLUP混合模型在PD和MCC法的基础上提出了改进的预期差法,以解决目前一些地区在评定公牛时缺乏谱系遗传值资料和微机的问题。作者用在成渝两地使用的26头黑白花种公牛的2126头女儿的头胎产奶记录,应用上述方法对26头公牛进行了评定。结果表明,两两方法排列的公牛序列间的差异均不大,改进的预期差法较适用于四川目前的情况。  相似文献   

11.
The current crisis in American archeology has been brought about by a combination of the greatly increased rate of destruction of unique, irreplaceable archeological information and material, and the lack of adequate funding for salvage of what is being destroyed. Since World War II, land alteration has increased almost geometrically. Land leveling, urban development, inexperienced or ignorant diggers, commercial dealers in Indian relics-these and many other agents of destruction are obliterating traces of the past. Anything that disturbs the ground where people once lived destroys forever whatever information is left about them and their way of life. Interpretations of man's cultural development through time, of his ability to cope with and use the environment wisely, and of a long, fascinating, and irreplaceable heritage are only possible if the evidence left in the ground is undisturbed and is properly recorded when it is excavated. The problem of the destruction of archeological sites and information is a complex one, with no single solution. A combination of increased support for archeological research through increased funding, and development of a knowledgeable, interested public will go a long way toward assuring this country that a significant portion of the past will be available for the benefit of future generations. If solutions are not sought and found now, it will be too late-we will have committed ourselves, irretrievably and irreversibly, to the future, without benefit or knowledge of the mistakes and the lessons of the past.  相似文献   

12.
New paleomagnetic, paleontologic, and stratigraphic data from outcrops of the Laytonville Limestone (101 to 88 million years old) support a Southern Hemisphere origin. A paleomagnetic megaconglomerate test is statistically significant and suggests magnetization at 14 degrees +/- 5 degrees south, predating Late Cretaceous to Eocene (70 to 50 million years ago) accretion. Rapid Kula plate movement or the existence and demise of a now vanished oceanic plate (or both) are required to accommodate the greater than 50 degrees of poleward displacement implied by the paleomagnetic data. This rapid motion brings into question the validity of a "speed limit" for absolute plate velocity based on present-day plate motions.  相似文献   

13.
Recent archeological fieldwork on the north coast of Peru permits a preliminary reconstruction of a prill-extraction copper and copper alloy smelting process heretofore undocumented in the New World. The process was applied on a large scale during the late pre-Hispanic period. This study provides strong support for the claim that central Andean metallurgy constituted one of the major independent metallurgical traditions of the world.  相似文献   

14.
Recently discovered deposits of obsidian in the Koyukuk valley may be the long-sought-for source of obsidian found in archeological sites in northwestern Alaska. Obsidian from these deposits compares favorably in physical characteristics and sodium-manganese ratio with the archeological obsidian, and there is evidence that the deposits have been "mined" in the past.  相似文献   

15.
Eggshells of the African ostrich (Struthio camelus), ubiquitous in archeological sites in Africa, have been shown by laboratory simulation experiments to retain their indigenous organic matrix residues during diagenesis far better than any other calcified tissue yet studied. The rate of L-isoleucine epimerization to D-alloisoleucine follows reversible first-order kinetics and has been calibrated for local temperature effects and used to estimate the age range of stratified archeological sites. Age estimates are consistent with radiocarbon dates from several stratified archeological sites. With adequate calibration, this technique can provide accurate ages to within 10 to 15 percent for strata deposited within the last 200,000 years in the tropics and the last 1,000,000 years in colder regions such as China.  相似文献   

16.
Theoretical work on the magnetohydrodynamics of the earth's liquid core indicates (a) that horizontal variations in the properties of the core-mantle interface that would escape detection by modern seismological methods might nevertheless produce measurable geomagnetic effects; (b) that the rate of drift, relative to the earth's surface, of nonaxisymmetric features of the main geomagnetic field might be much faster than the average zonal speed of hydrodynamic motion of core material relative to the surrounding mantle; and (c) why magnetic astronomical bodies usually rotate. Among the consequences of (a) and (b) are the possibilities that (i) the shortest interval of time that can be resolved in paleomagnetic studies of the geocentric axial dipole component of the earth's magnetic field might be very much longer than the value often assumed by many paleomagnetic workers, (ii) reversals in sign of the geomagnetic dipole might be expected to show some degree of correlation with processes due to motions in the mantle (for example, tectonic activity, polar wandering), and (iii) variations in the length of the day that have hitherto been tentatively attributed to core motions may be due to some other cause.  相似文献   

17.
Alternating translucent and opaque bands on the roots of mammal teeth are used to determine the age and season of death. These structures are preserved in teeth from archeological sites. However, the standard sectioning technique, which includes decalcification, often destroys archeological specimens. A new, less destructive technique provides analyzable solid sections at costs comparable to decalcification.  相似文献   

18.
Considering the unique morphology (purposefully shaped polished bar with a groove) and composition (magnetic mineral with magnetic moment vector in the floating plane) of M-160, and acknowledging that the Olmec were a sophisticated people who possessed advanced knowledge and skill in working iron ore minerals, I would suggest for consideration that the Early Formative artifact M-160 was probably manufactured and used as what I have called a zeroth-order compass, if not a first-order compass. The data I have presented in this article support this hypothesis, although they are not sufficient to prove it. That M-160 could be used today as a geomagnetically directed pointer is undeniable. The original whole bar may indeed have pointed close to magnetic north-south. The groove functions well as a sighting mark, and the slight angle it makes with the axis of the bar appears to be the result of calibration rather than accident. A negative supporting argument is that M-160 looks utilitarian rather than decorative, and no function for the object other than that of a compass pointer has been suggested by anyone who has examined it critically. Whether such a pointer would have been used to point to something astronomical (zeroth-order compass) or to geomagnetic north-south (first-order compass) is entirely open to speculation. The observation of the family of Olmec site alignments 8 degrees west of north is a curiosity in its own right, and the possibility that these alignments have an astronomical or geomagnetic origin should be explored. I also believe that it is constructive to compare the first millennium Chinese, who used the lodestone compass for geomancy, with the Gulf Coast Olmec since both were agrarian-terrestrial societies. The Olmec's apparent concern with orientation and skillful use of magnetic minerals also stimulates one to draw cross-cultural parallels. The evidence and analysis offered in this article provide a basis for hypotheses of parallel cultural developments in China and the Olmec New World. If the Olmec did discover the geomagnetic orienting properties of lodestone, as did the Han Chinese, it is most reasonable to speculate that they would have used their compass for comparable geomantic purposes. It should, however, be recognized that the Olmec claim, if documented, predates the Chinese discovery of the geomagnetic lodestone compass by more than a millennium. At present, M-160 is a unique artifact and San Lorenzo a unique site: "The first civilized center of Mesoamerica and probably of the New World" (19, p. 89). Further documentation of the Olmec claim must await the discovery of similar artifacts in museums, private collections, or as yet undiscovered Olmec sites. I would welcome communications from anyone possessing information relating to such artifacts. Regardless of shape, purposefully grooved and highly polished specimens of magnetic minerals are of particular interest. It would also be useful for the archeologist excavating Olmec burials and offerings to carefully note their alignments and consider them in a geomantic context. In addition to the discovery of supporting artifacts, establishment of Olmec primacy of the lodestone compass depends on the acquisition of the archeomagnetic data for the Early Formative period. I appeal to archeologists who find good archeomagnetic samples (burned hearths and post-holes) from the Formative periods to convey this information to R. DuBois of the University of Oklahoma. In a few years, the archeomagnetic data should be available for the last three millennia and the possibilities are very exciting.  相似文献   

19.
Cotton remains from four archeological sites in central coastal Peru, representing a time sequence from about 2500 to 1000 B.C., were compared with similar materials obtained from living wild and cultivated forms of Gossypium barbadense L. The comparison revealed that the archeological cotton samples were primitive forms of Gossypium barbadense, differing little from present-day wild forms of the same species. Although not the earliest cottons recorded for the New World, they appear to represent the earliest stages of cotton domestication yet recorded.  相似文献   

20.
Angrites are among the oldest known pristine basaltic meteorites and record the earliest stages of planet formation and differentiation. Our paleomagnetic analysis of three angrites found that they record a past magnetic field of approximately 10 microteslas on the angrite parent body extending from 4564 to at least 4558 million years ago. Because the angrite paleomagnetic record extends beyond the expected lifetime of the early circumstellar disk, these paleofields were probably generated internally on the angrite parent body, possibly by an early dynamo in a rapidly formed metallic core.  相似文献   

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