摘要:

AbstractPaleoenvironmental data from the Atacama Altiplano (21°–24°S) indicate that water, vegetation and animal resources were more abundant during lateglacial and early Holocene times than today. The rate of precipitation increased above 4000 m elevation to 400–500 mm/yr compared to the present 200 mm/yr. Dry conditions prevailed below 3500 m. Evidence of Paleoindian habitation is still missing, even though there is no evidence for environmental prohibitors during lateglacial time. The early Archaic hunters (10,820 yr B.P.‐ca. 8500 yr B.P.) inhabited the Altiplano (high Puna) and its western slope, where water was available due to higher river runoff from the Altiplano, and the resources in different elevation zones were accessible. Natural resources decreased significantly during the middle Archaic period (8500‐ca. 5000 yr B.P.). Lakes receded to today's levels, pedogenesis in the Altiplano terminated, and human activities were restricted to the most stable sites in the Río Lao and the Río Purifica catchments north of 23°S. The less stable oases south of 23°S (Salar de Atacama and Punta Negra) were abandoned. The climatic changes are best explained by shifts of the (sub)tropical circulation. © 1994 John W

ISSN:0883-6353    

DOI:10.1002/gea.3340090402

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractGeoarchaeological studies using geomorphological, lithological, cryolithological, palynological, paleomagnetic, thermoluminescent, and plant macrofossil analyses have been conducted on the Diring site, eastern Siberia. Mochanov (1988a, 1988b) assumed that the sediments which overlay the Diring cultural layer are synchronous with the Tabaga terrace of the Lena River (Upper Pliocene) and dated the cultural layer 1.8–3.2 My ago. Alekseev et al. (1990b) concluded that the cultural layer could not have dated earlier than the Late Eopleistocene, i.e., 0.8–1.8 My ago. Ranov and Tseitlin (1991) assumed that the cultural layer is of Middle Pleistocene age, 250–300 Ky ago. Based on a review of the geoarcheological analyses and new examination of the site in 1990, it is concluded that the cultural layer at Diring is of Late Pleistocene age. © 1994 John Wiley&Son

ISSN:0883-6353    

DOI:10.1002/gea.3340090403

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA method for determination of volcanic glass concentration in sedimentary sequences is presented. This method consists of two steps: (1) systematic extraction of volcanic glass particles from samples taken at close intervals in a sedimentary section, and the determination of their concentration; (2) precise measurement of the refractive indices of the separated glass particles. A recently developed measuring system (RIMS 86) based on the thermal immersion method permits quick and accurate measurement of the refractive index of a large number of grains within samples. Based on these kinds of data, we typically recognize five types of concentration of volcanic glass shards in sedimentary sequences. The method proposed here enables the simultaneous determination of the refractive index of glass shards and the proportion of glass shards in a sample, which makes it possible to recognize certain ash‐fall‐horizons, even those undetectable through visual observation of a sedimentary column. © 1994 John Wiley&Sons,

ISSN:0883-6353    

DOI:10.1002/gea.3340090404

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractWork on the excavations at the ancient Etruscan settlement of Marzabotto (Bologna) restarted in 1988. These excavations, as they were worked, brought to light a complete urban layout represented primarily by foundations, courtyards, roads and wells. The site has been the focus of intensive experimentation to assess the feasibility of geophysical remote sensing in exploration archaeology. Different geophysical techniques have been tested at this site: geoelectric, electromagnetic, magnetic, and seismic methods. One of the methods tested was geophysical seismic tomography. This method utilizes straightray algorithms to map subsurface properties by analyzing the first signal arrival time. Seismic tomography treats the problem of identifying a buried structure as a wave propagation process by inverting the linearized wave equation to compute the spatial distribution of the slowness of the velocity. The purpose of our tomographic study is to further test the method and to guide archaeologists in their future excavations by locating and identifying buried structures. In particular, analyses are performed on the geometries, signal characteristics, discretization of the area, and constraints of the inversion algorithm in order to enhance the effectiveness of the tomographic reconstruction process and to reduce costs. A controlled experiment is presented for a typical Marzabotto buried structure with which it is possible to verify the effectiveness of the applied technique. It is demonstrated how proper field measures and an inversion test can provide reliable information that can be used to guide excavation work. © 1994 John Wiley&Sons, Inc

ISSN:0883-6353    

DOI:10.1002/gea.3340090405

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

ISSN:0883-6353    

DOI:10.1002/gea.3340090406

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

ISSN:0883-6353    

DOI:10.1002/gea.3340090407

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

ISSN:0883-6353    

DOI:10.1002/gea.3340090408

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

ISSN:0883-6353    

DOI:10.1002/gea.3340090409

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

ISSN:0883-6353    

DOI:10.1002/gea.3340090401

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY