Gamma Log Trend Facies in the Choshui Fan-Delta,Taiwan

This study uses paleomagnetic methods to analyze the tectonic featuresin the northeastern coastal area of Taiwan.A total of 14 sites were chosenat the different locations where slightly metamorphosed and multiply deformedsedimentary strata are characterized by gently dipping folds anddense-spaced faults.The results show that the paleo-inclinations of all thesites are negative.This suggests that the characteristic paleomagnetic directionswere acquired during magnetic time zones of reversed polarity.The paleo-declinations measured are very scattered.However,after thebedding of each studied site is rotated to the regional structural attitude innortheastern Taiwan,there is a consistent trend at approximately N80°E;most of the corrected paleomagnetic directions point toward the directionof N100°E-N120°E.Micro-tectonic analysis also deciphered the direction ofthe major compression in the area studied,which occurred in the sameperiod as that of corrected paleomagnetic direction.This suggests that thepaleomagnetic directions of the samples in the studied area were acquiredbefore the major folding and faulting which caused great deal of horizontalrotation in both clockwise and counterclockwise senses.In addition,thecorrected paleomagnetic directions do not show an expected direction in anormal or reversed polarity epoch.This implies that they may not be theprimary component of NRM acquired during the deposition of the formations.Instead,they might result from regional metamorphism/deformationwith a certain degree of intensity.Thus,the results reveal that thesamples studied have acquired the remanent anisotropy of their magnetizations.

並列關鍵字

Well Logging ； Gamma Log Trend ； Choshui Fan-Delta ； Hydrogeology

國際替代計量

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