Beitrag
The Gravity Field and Crustal Structure of Iran
Dehghani, G. A.; Makris, J.
Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen Band 168 Heft 2-3 (1984), p. 215 - 229
10 Literaturangaben
veröffentlicht: Jun 28, 1984
Online veröffentlicht: Jul 27, 2018
DOI: 10.1127/njgpa/168/1984/215
ArtNo. ESP155016802006, Preis: 29.00 €
Abstract
By evaluating 10.000 gravity stations in terms of Bouguer, isostatic, geoid deformation and crustal thickness maps of Iran, the following results were obtained: The gravity field of the Zagros Mountains shows minimum gravity values of -220 mGal. The gravity minimum strikes parallel to the Zagros Main Thrust, where the crustal thickness was found to be 55 km. At the morphologic depression of the Kavir and Lut Depressions the gravity field reaches values between -50 and -70 mGal, and the crust thins out to less than 40 km. In the east Iranian ranges gravity values of -130 to -160 mGal occur, and the crustal thickness inrceases again to values of 45 to 48 km. Along the Elburs Mountains in north Iran, the Bouguer gravity varies between -100 and -120 mGal, and the crustal thickness is less than 35 km. It is obvious that these mountains have no root. Most parts of Iran are isostatically balanced, and the computed isostatic anomalies are 0 ± 10 mGal. Execeptions are in the Zagros Main Thrust, where the structure seems to be undercompensated with isostatic anomalies of approximately -20 mGal. In the Elburs Mountains, the structure is overcompensated with values of +20 mGal. The transition zone between the Zagros Mountain Belt and the Makran Block of east Iran is heavily disturbed, and the anomalies locally reach values between +70 and -70 mGal. In east Iran, the province of Khusistan, residual gravity shows strong negative anomalies of approximately -60 mGal, associated with very thick sediments. Isostatically, this area is out of balance, and the locally computed anomalies exceed -60 mGal. The geoid deformations computed from free-air gravity and the GEM 10 B spherical harmonics show a gradual depression from north-west to south-east Iran. The rapid bending of the geoid isolines of a NS trend in central and northern Iran into an EW direction along the Zagros Belt is obviously caused by the tectonic compression, which is also responsible for the recent deformation of the Zagros Mountains.
Schlagworte
Gravity field • isostasy • geoid deformation • crustal structure • crustal thickness • Moho depth • gravity map • Iran