الفهرس | Only 14 pages are availabe for public view |
Abstract The present study is devoted fo::: the treatment and interpretation of the available geophysical data, utilizing the Boligller gravity data and the total ~ntens~ty land magnetic data, of the northwestern part of 1:he Sinai peninsula, Egypt. Northward of lat~tade 30° alternating faulted domes, anticlines and synclines known as tbe Syrian arc system form a contrasting topog:::a:;:hy of lew alluvial plains and high hill masses. Norther:o. sediments predominantly deposited in environment. Sinai is covered by a shallow platfo~ T~e Bouguer g=avity nap of ~~e studied area is interpreted in orde= to define the ve~t.ical ar.d lateral variations in the stratigraphy and structure of the sedi~entary section. First, the isolation cf the residual and regional anomalies is done on the Bouguer gravity nap, using Griffin’s method (1949). However, the residual gravity anomalies reflected the anomalies that result from shallow sources, but the regional gravity anomalies revealed the effects that produce from relatively deeper sources. In addition, filtering of the Bouguer gravity anomalies is also operated using regional filters, residual filters and band-pass filters. The regional filters passed long wavelengths of the regional anomalies of deep scl:rces with low frequencies and rejected all wavelengths smaller than the cut-off wavelength (Low-pass-filter). The residual filters passe~--s~o_rt __ wave~=ng:t~ _o_f _ ~[1_., ___ J,ccaJ, anomalies c:r: !>h~ll.91.’ sources with high frequencies and rejected al:. the wavelengths larger than the cut:-off wavelength (high-pass filter). The band-pass filter passed wavelengths within a eeztai:ii range and reJected the wavelengths shorter than the lower cut-off limit and longer than the upper cut-off limit. ’Ynis is done utilizing the filter operators 8-unit, 16-unit an 21.3 unit with the ranges betNeen then (16-B, 21.3-16 and 21.3-8 units). On the other hand, the importance and relationship of gravity anomalies (including the opt in= filtered residual, regional and band-pass gravity anomalies, as well as local a~d regional geologic condi~ions) are ~e:l-shcw~ ty ~~e five different orientation gravity pr·ofi:es. These pr:::files are interpreted ttuough the two-di~ensional complex gravity Modelling to constr~ct the subsurface structural pattern along them. Moreover, the gravity structures are delineated within the sedimentary section, as ·well as the underlying basement complex in the form of fault segments (elements) at different depths using Linsser’s method (1967). However, the systems of faulting dissecting the whole sediment:ary colllifu~, as well as those intervening the depth ranges of 2.0,3.0,4.0 and 5.0 kms are defined with respect to their trends, throws, effects and coincidence. Finally/ the predomi~ant st~4ct~ra: ~re~ds of the faul~ ele:nents, which delineated fron the gravi -:.y detailing are as follows: - NE-SW (ENE) trend (Syrian arc system). ·· ·~-m;=:;E ~·end - ·(Re-a-s-ea sys~emT; E-W (WNW) trend (Mediterranean sea system). NNE-SSW trend (Aqaba system) . Al.so, the land survey of the total intensity magnetic ----and Geophysies is analyzed in ter:ns -cf·· basewei,~ · pa!. ameler. First, this total intensity land magnetic map of the studied area is reduced to the pole to eliminate the distortions occurred in the distribution of ~~e exis~ed magnetic anomalies due the . ., . ~. l.nC..~...l.na .... .l.on of the measured nor:nal magnetic field. Then, the separation of t!:le residual and regional anomalies is done on both the total intensity land magnetic data and the reduced to 1:!:le J:agnetic pole data utilizing Griffin’s method (1949). The two residual maps and the two regional maps are generally si:nilar, but the :naps derived from the reduced to the pole data are shifted northward with more resolution, as ccnpared with the maps derived from the total intensity land magnetic map. On the other hand, filtering of the total intensity magnetic and the reduced to the pole anomalies is also operated utilizing the same filters, which were used before in the treatment of the gravity anonalies. By the same way, this proved to be helpful in isolating ~~e residual anomalies from the regional ones from the anonalies existed within a certain interval of depth. Moreove:::-, the application of these filters and their operators on the st~died gravity and magnetic data reveals that; the 8-unit residual fil~er is the cptim= for delineating the $ID3.ller ele::~ents of shallow depths on the expense of the 16 and 21. 3 units; the 21. 3 regional filter is the best for defining the larger elements of deep dep~hs on the emense of tbe----8 and 16 units A) Si 1 1 the 21.3-8 band-pass filter is tJJ.e adequate for following the inferences of ~n~ermedlate depth range on the expense of the 16-8 and 21.3-16 units. Added, the parameters (depth, -wi::J.t:: and azimuth) of the dyke system intervening the basenent su~face of the investigated area are deternined usi:1g C::urant’:1y and drys (1963) and powell (1956&1967) techni~~es. Accordingly, a basement relief :n.ap wi t:r.. the nar.:..::es-:.ed dykes is dra~wn, showing more or less the configuration of the basement surface in the area and the related igneous activities. Therefore, the basement of such area is characterized by a swell trending NNW-SSE at the central part, changed at the northern part to be nearly NE-SW t!:”er’.d, :.n addition, ”three troughs trending NNE-SSW at the eastern part, NW-SE at the sout..>J.western corner and E-W at the northern part. The inspection of the regional and residual gravity and magnetic anomalies as well as the results of application of the other interpretational methods on the potential field data ::-eveals the subdi visicn cf the i:1vestigateC . ~ area .:.n ..... o normal fault t~xowing westward. The eastern portion with two Jnonnal faults t~cwing out·t~ard.ly rep::=-ese:-1--:.s a harst block implicated by Gifgafa and Maghara an~ic:inal trends, as well as El-Laga::na and El-Hassana syncl.:..r.a: t~ends, all nearly directing ENE-WSW. Alsc;-, o-c.her normal faults -chrowing inwardly represenc:s a graben block manifested by Gilbana and El-KantaTa anticlinal trends as well as El-Abd and lsmalJ.a s:r-nclJ.nal -.:rendS, all nearly implied ty the longitudinal ~ina-El Barda•il Synclinal trend |