LATE PERMIAN TO EARLY TRIASSIC MAGNETOSTRATIGRAPHY

被引:68
作者
HAAG, M
HELLER, F
机构
[1] Institut für Geophysik, ETH-Hönggerberg
关键词
D O I
10.1016/0012-821X(91)90042-G
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
A Late Permian to Early Triassic magnetostratigraphic reference section is presented. The Lower Triassic part is based on results from marine limestone sections in South China published earlier [1,2]. Reliable new Permian data are added here which have been collected in the Nammal gorge (Salt Range, Northwest Pakistan) where marine sediments have been deposited quasi-continuously with occasional minor hiatuses during the late Palaeozoic to early Mesozoic. About 50% of the Permian samples from the Nammal section contain, hidden beneath a strong recent or Tertiary overprint, a characteristic remanent magnetization (ChRM) which is very likely of Permian age. This component, which was imprinted on the southern hemisphere, has normal as well as reversed polarity with a normal mean direction (Decl. = 289.3-degrees, Incl. = -50.3-degrees, alpha-95 = 4.3-degrees, N = 113) which is in close agreement with the palaeofield direction expected for a site belonging to the Indian plate as part of Gondwanaland during the Permian. In the lower Upper Permian several normal polarity zones are recognized. This contradicts the current assumption that rocks of this age belong to the long, reversely polarized Kiaman hyperzone. The Kiaman interval must end and the Illawarra hyperzone of mixed polarity must begin in or prior to the lowermost Upper Permian. The Permian/Triassic boundary at Nammal as well as in the Chinese sections is situated very close to a transition from a reversed to a normal polarity zone. The Upper Permian at Nammal together with the Lower Triassic South China sections is estimated to cover about 20 Ma. Nearly 30 polarity changes are observed which result in an average reversal frequency very similar to that observed during the early Tertiary. The reversal rate after the end of the long-lasting reversed Kiaman hyperchron apparently increases in a manner similar to that after the end of the Cretaceous Long Normal Superchron. Only a few polarity zones are found in the lower Upper Permian, while progressively more frequent reversals follow in the Lower Triassic.
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页码:42 / 54
页数:13
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共 36 条
  • [1] PERMIAN-TRIASSIC OF THE TETHYS - CARBON ISOTOPE STUDIES
    BAUD, A
    MAGARITZ, M
    HOLSER, WT
    [J]. GEOLOGISCHE RUNDSCHAU, 1989, 78 (02): : 649 - 677
  • [2] BOSSART P, 1989, ECLOGAE GEOL HELV, V82, P585
  • [3] DISPERSION ON A SPHERE
    FISHER, R
    [J]. PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES A-MATHEMATICAL AND PHYSICAL SCIENCES, 1953, 217 (1130): : 295 - 305
  • [4] GEE ER, 1947, NAT ACAD SCI INDIA B, V14, P95
  • [5] MAGNETOMETERS USING RF-DRIVEN SQUIDS AND THEIR APPLICATIONS IN ROCK MAGNETISM AND PALEOMAGNETISM
    GOREE, WS
    FULLER, M
    [J]. REVIEWS OF GEOPHYSICS, 1976, 14 (04) : 591 - 608
  • [6] HAAG M, 1989, THESIS ETH ZURICH
  • [7] HAQ BU, 1987, GEOLOGICAL TIME TABL
  • [8] MAGNETOSTRATIGRAPHY OF THE PERMO-TRIASSIC BOUNDARY SECTION AT SHANGSI (GUANGYUAN, SICHUAN PROVINCE, CHINA)
    HELLER, F
    LOWRIE, W
    LI, HM
    WANG, JD
    [J]. EARTH AND PLANETARY SCIENCE LETTERS, 1988, 88 (3-4) : 348 - 356
  • [9] HELLER F, 1978, J GEOPHYS-Z GEOPHYS, V44, P525
  • [10] HELSLEY CE, 1974, GEOL SOC AM BULL, V85, P457, DOI 10.1130/0016-7606(1974)85<457:POTLTM>2.0.CO