The geodynamic evolution of the Internal Zone of the Betic Cordilleras (south-east Spain): a model based on structural analysis and geothermobarometry   总被引：2，自引：0，他引：2  

H. E. BAKKER  K. DE JONG  H. HELMERS  C. BIERMANN 《Journal of Metamorphic Geology》1989,7(3):359-381

ABSTRACT The Internal Zone of the Betic Cordilleras consists of several superimposed major thrust sheets with different P-T-t evolutions. On the basis of an integrated field, microscopic and laboratory study, the tectono-metamorphic history of the Mulhacen Complex and Almanzora Unit has been reconstructed in detail. The Mulhacen Complex has been affected by at least five phases of penetrative deformation, which have been labelled D_x-1, D_x, D_x+1, D_x+2 and D_x+3. D_x-1, and D_x are related to continent-continent collision, which is indicated by high pressure-low temperature (HP/LT) and subsequent intermediate P/T metamorphic conditions. D_x+1 is related to crustal thinning and heterogeneous extension. During this event the Almanzora Unit was juxtaposed against the Mulhacen Complex. This phase was succeeded by the establishment of low pressure-high temperature (LP/HT) conditions and at least two phases of folding and overthrusting. The Almanzora Unit shows a comparable tectono-metamorphic evolution post D_x+1. However, the P/T conditions prior to D_x+1 indicate a higher crustal position with respect to the Mulhacen Complex during the collisional event.  相似文献   

Milankovitch cyclicity in Purbeck peritidal limestones of the Prebetic (Berriasian, southern Spain)   总被引：1，自引：0，他引：1  

C. JIMENEZ DE  CISNEROS J. A. VERA† 《Sedimentology》1993,40(3):513-537

Peritidal carbonate rocks (Purbeck facies) of the uppermost Portlandian to Berriasian in the type section of the Sierra del Pozo Formation in the Prebetic Zone, southern Spain, are divisible into 141 shallowing upward cycles averaging 2 m in thickness. The subtidal facies in these cycles consist of micritic or marly limestones with dasycladacean algae and lituolids; the intertidal facies are micritic limestones containing birdseyes and miliolids; the supratidal facies comprise laminated algal limestones, the tops of which display desiccation cracks and rhizocretions, or more locally palaeosols, calcretes, or palaeokarst surfaces. A statistical study, using power spectra of the Fast Fourier Transform, demonstrates that the periodicity of these cycles is in the Milankovitch frequency band. Most sedimentary cycles correspond to the obliquity cycles; eccentricity and precession cycles have also been recognized. Using a Fischer plot, third-order tectono-eustatic cycles are recognized, which can be correlated with the eustatic curve of the Exxon chart. The shallowing upward sequences are characterized by a distinctive pattern of geochemical parameters. Carbon and oxygen isotopic (δ¹³C and δ¹⁸O) variations, calcium and magnesium carbonate contents and the abundance of organic matter and trace elements (Mn and Sr) all have predictable patterns of distribution within the sequences. The Sr content of the subtidal facies is relatively high whereas the δ¹³C and δ¹⁸O ratios are quite low; in the intertidal facies the Sr and Mn levels fall concomitantly with a rise in δ¹³C and δ¹⁸O. The highest δ¹³C and δ¹⁸O values occur in the lower part of the supratidal facies, whereas in the upper part of δ values and Sr contents drop sharply. Cyclic variations in evaporation and in meteoric water influence, determined from oxygen isotopic composition, reveal that the cyclicity of the beds containing the most limestones (supratidal) and those with the most marls (subtidal) is related to climatic changes. The coldest periods are those represented by supratidal deposits, when the sea level was at its lowest. During the warmest periods, when the overall sea level was higher, subtidal deposits accumulated in the region. A genetic model is proposed, according to which the asymmetrical sedimentary cycles occur in response to glacio-eustatic changes with a periodicity similar to that of Plio-Pleistocene sea-level variations, but with a much lower range due to the smaller extent of polar ice caps during the Early Cretaceous. The glacio-eustatic changes involved a rapid sea-level rise and a slow sea-level fall.  相似文献   

Distribution and numbers of breeding ivory gulls Pagophila eburnea in Severnaja Zemlja, Russian Arctic     

ANDREJ E. VOLKOV  JACOBUS DE KORTE 《Polar research》1996,15(1):11-21

The ivory gull Pagophila eburnea has a semi-circumpolar distribution with breeding sites in the High Arctic. Data about ivory gulls in the Severnaja Zemlja Archipelago (Siberia) were collected from 1991 to 1995. The numbers of breeding ivory gulls and their egg-laying period arc correlated with the sea ice situation and weather during the first part of the summer. We estimate that the total potential breeding population of Severnaja Zemlja is about 2000 pairs, which makes up approximately 20% of the Russian and 14% of the world ivory gull breeding population. The percentage of the total breeding population which actually breeds varies annually. The most important breeding area of the ivory gull in Severnaja Zemlja is the Sedov Archipelago (A. Sedova) where a large colony (from 410 to about 1100 pairs in different years) was found on flat ground on Domašmj Island. Colonies from 10 to 100 breeding pairs, mostly on steep cliff faces, occur on O. Oktjabr'skoj Revoljucii and O. Boľševik. The ivory gull is included in the Red Data Book of Russia. Parts of Severnaja Zemlja. with important breeding sites, have become a nature reserve.  相似文献   

ANALYSIS OF THE COMMON MIDPOINT GATHER BY DECOMPOSITION INTO ELEMENTARY WAVEFRONTS1     

PIERRE THORE  ERIC DE BAZELAIRE 《Geophysical Prospecting》1991,39(4):453-471

The imaginary wavefront of a common midpoint gather of seismic data is analysed in terms of elementary wavefronts. The wavefronts emitted by the sources are split into a sequence of elementary circular wavefronts. Each such wavefront is independently transmitted through the subsurface and received by a group of receivers associated with the sources. The theory is first demonstrated in the case of a one-layer medium and is then extended to the case of a multilayer medium. We show that pairs of imaginary stationary points F and F' occur in the first medium through which all the rays, corresponding to the group of sources and receivers associated with the elementary wavefront pass. The location of the points is determined by 2n equations with 2n unknowns; (2n - 1) of these equations correspond to n layers of the medium, and an additional equation is given by the geometry of the CMP gather. Applying Fermat's principle between the points F and F', we obtain an algorithm for CMP ray tracing. The wavefront sampling problem is considered but not theoretically solved. Results obtained in the general case (a multilayer medium with lateral velocity variation) are presented and compared with those obtained by other modelling techniques.  相似文献   

ON THE BASAL BEDS OF THE SEDIMENTARY SERIES IN SOUTHWESTERN SHANSI     

E.LICENT  P.TEILHARD DE CHARDIN 《地质学报》1927,6(1):61-64

During the summer of 1926, when visiting some of the mountain rang-es of the Southwestern Shansi, we noticed, in two localities, some interestingfacts concerning the basal beds of the Sinian or the Cambrian, and their rela-tions with the underlying ctystalline rocks.  相似文献   

ON SOME NEOLITHIC (AND POSSIBLY PALAEOLITHIC) FINDS IN MONGOLIA,SINKIANG AND WEST CHINA     

德日進  楊鍾健 《地质学报》1933,(0)

In the course of the past two years,when they were in the field with theThird American (1930) and the Haardt-Citroen (1931) Central Asiatic Expedi-tions,the authors of the present note had opportunities for making a series ofarchaeological observations over an extensive area.It seems interesting to report  相似文献   

GEOLOGICAL STUDY OF THE DEPOSITS OF THE SANGKANHO BASIN.     

G.B.BARBOUR  E.LICENT  P.TEILHARD DE CHARDIN 《地质学报》1926,5(3)

This paper offers a preliminary statement of the results of investigations carried out in the South Sangkanho basin, in the mountains some 80 miles to the NW of Peking. Important fossiliferous deposits found in this area throw light on the conditions ruling in N. China during the transition from Pliocene  相似文献   

NOTE SUR LA STRUCTURE DES MONTAGNES A L''OUEST DE LINN MING KWAN (CHIHLI MERIDIONAL).     

PAR P.TEIHARD DE CHARDIN 《地质学报》1924,3(3):393-397

En Fevrier 1924, j'ai eu l'occasion, (guide par le P. Charvet, professeur a l'Institut des Hautes Etudes Industrielles de Tientsin), de traverser la region montagneuse comprise entre Linn Ming Kwan et le Zeu Chan, petit massif situe a une trentaine de kilometres ouest de Linn Ming  相似文献   

ON THE GEOLOGY OF THE NORTHERN, WESTERN AND SOUTHERN BORDERS OF THE ORDOS, CHINA   总被引：16，自引：0，他引：16  

TEILHARD DE CHARDIN  F. LICENT. 《地质学报》1924,3(1):37-44

During the last summer (1923), the authors of this paper were sent by the National Museum of Paris and by the French Ministere de l'Instruction publique for a geological mission in Inner Mongolia. Leaving from Pao T'eou, the geologists crossed the Oula Shan, took a view of the Scheiten Oula  相似文献   

Radiocarbon analyses along the EDML ice core in Antarctica     

R. S. W. VAN DE WAL  H. A. J. MEIJER  M. DE ROOIJ  C. VAN DER VEEN 《Tellus. Series B, Chemical and physical meteorology》2007,59(1):157-165

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