Private property—national legacy: Protecting privately owned archaeological sites in the united states     

Mark Michel 《Natural Resources Research》1997,6(2):131-136

  相似文献   

Partition, die Wende, and German unification     

Mark Blacksell 《Applied geography (Sevenoaks, England)》1997,17(4):257-265

This paper provides a geographical context and overview of the critical steps leading to German unification on 3 October 1990. It examines the extent to which the whole process was typical of the sequence of events in other states that have been partitioned and have subsequently reunited, with particular reference to the so-called Wende in East Germany. This was a spontaneous, popular movement for internal reform which, spurred on in late 1989 by the impending collapse of the East German government and its protector, the Soviet Union, became a rallying point for German unification.  相似文献   

Aspects of German unification     

Mark Blacksell  Fiona M. Smith 《Applied geography (Sevenoaks, England)》1997,17(4):255-256

  相似文献   

Magnetic properties of hydrothermally synthesized greigite (Fe₃S₄)—I. Rock magnetic parameters at room temperature     

Mark J. Dekkers  Martin A. A. Schoonen 《Geophysical Journal International》1996,126(2):360-368

  相似文献   

Yucatán karst features and the size of Chicxulub crater     

Martin Connors  Alan R. Hildebrand  Mark Pilkington  Carlos Ortiz-Aleman  Rene E. Chavez  Jaime Urrutia-Fucugauchi  Eduardo Graniel-Castro  Alfredo Camara-Zi  Juan Vasquez  John F. Halpenny 《Geophysical Journal International》1996,127(3):F11-F14

The buried Chicxulub impact structure is marked by a dramatic ring of sinkholes (called cenotes if containing water), and adjacent less prominent partial rings, which have been shown to coincide with maxima in horizontal gravity gradients and a topographic depression. These observations, along with the discreteness and spacing of the features, suggest a formation mechanism involving faulting in the outer slump zone of the crater, which would thus have a diameter of approximately 180 km.
An opposing view, based primarily on the interpretation of gravity data, is that (he crater is much larger than the cenote ring implies. Given the association of the known cenote ring with faults, we here examine northern Yucatan for similar rings in gravity, surface features and elevation, which we might expect to be associated with outer concentric faults in the case of a larger, possibly multiring, structure.
No such outer rings have been found, although definite patterns are seen in the distribution of karst features outside the crater rim. We explain these patterns as resulting mainly from deformation related to the block fault zone that parallels tbe shelf edge of eastern Yucatan.  相似文献   

Petrogenesis of lavas from the AMAR Valley and Narrowgate region of the FAMOUS Valley, 36°–37°N on the Mid-Atlantic Ridge     

A. P. le Roex  Frederick A. Frey  Stephen H. Richardson 《Contributions to Mineralogy and Petrology》1996,124(2):167-184

Basaltic lavas from the AMAR Valley and the Narrowgate region of the FAMOUS Valley on the Mid-Atlantic Ridge (36° to 37°?N) range in texture from aphyric to highly plagioclase phyric (>25% large plagioclase phenocrysts). Based on ⁸⁷Sr/⁸⁶Sr and ¹⁴³Nd/¹⁴⁴Nd ratios, most of these lavas can be subdivided into two distinct, isotopically homogeneous, groups: Group I has lower ⁸⁷Sr/⁸⁶Sr (0.70288±1) and higher ¹⁴³Nd/¹⁴⁴Nd (0.51312±1) ratios; Group II has higher ⁸⁷Sr/⁸⁶Sr (0.70296±1) and lower ¹⁴³Nd/¹⁴⁴Nd (0.51309±2) ratios. Most Group II lavas are aphyric, whereas Group I lavas are primarily plagioclase phyric. Lavas from both groups show a wide range in incompatible element abundance ratios (e.g., Zr/Nb =6–29; (La/Sm)_n=0.6–1.7). Aphyric lavas have relatively constant Sc (40±1.5?ppm) abundances and CaO/Al₂O₃ ratios (0.80±0.02). Group I lavas are confined primarily to the AMAR rift valley floor whereas Group II lavas are found along the east and west marginal highs. We interpret the isotopic differences between the two groups as reflecting a temporal change in the upwelling mantle beneath this region of the Mid-Atlantic Ridge which is south of the Azore Islands. For each group, a petrogenetic model consistent with the geochemical data is multi-stage decompression melting of an initially enriched, homogeneous, mantle source region. If the early derived, incompatible-element enriched, melt increments are not always pooled with subsequent increments, the erupted magma batches may have the major element characteristics of melts derived by 10 to 20% melting, but with incompatible element abundance ratios reflecting the change from an enriched to depleted source during the incremental melting process. In this process an initially homogeneous source can generate primary magmas with the required range in incompatible element abundance ratios shown by each group. The nearly constant CaO/Al₂O₃ ratios and Sc contents of the aphyric lavas with decreasing Mg?? reflects subsequent polybaric fractionation of clinopyroxene, plagioclase and olivine over the pressure interval 8–6?kbar (24–18?km), followed by rapid transport to the surface and eruption. There is no geochemical evidence for a crustal magma chamber beneath this section of the Mid-Atlantic Ridge.  相似文献   

Organic Carbon Dominated Trichloroethene Sorption in a Clay-Rich Glacial Deposit   总被引：1，自引：0，他引：1  

Richelle M. Allen-King  Larry D. McKay  Mark R. Trudell 《Ground water》1997,35(1):124-130

  相似文献   

Estimation of α_L, Velocity, K_d and Confidence Limits from Tracer Injection Test Data     

James Broermann  R.L. Bassett  Edwin P. Weeks  Mark Borgstrom 《Ground water》1997,35(6):1066-1076

  相似文献   

A Survey of the Causes of Surfactant-Induced Changes in Hydraulic Conductivity   总被引：1，自引：0，他引：1  

Mark A. Tumeo 《Ground Water Monitoring & Remediation》1997,17(4):138-144

  相似文献   

Compressional wave velocity and attenuation at ultrasonic and sonic frequencies in near-surface sedimentary rocks     

Angus I. Best  Mark S. Sams 《Geophysical Prospecting》1997,45(2):327-344

  相似文献