| Summary: | 碩士 === 國立中央大學 === 地球物理研究所 === 87 === The electrostratigraphy in the coastal plain between Peikang-chi and Pachang-chi was studies by using Direct current resistivity method. Incorporating of the sounding data with the geological well information were used to discuss the changes of depositional environment and the aquifer distribution. In addition, combined the dc data obtained in the Chiayi with those in the Tainan area to investigate the changes of the paleo-coastline was also included in this study. Based on the final results, several conclusions can be drawn:
1. Based on the subsurface electrical characteristics, the higher resistivity zone ( >40Ω-m ) in the northeastern side may cause by the sediments from Peikang-chi, and the lower resistivity zone ( <20Ω-m ) in the western side reflect a marine and shore facies.
2. The sediments in the whole area are mainly consisted of the alternation of sand and mud. Thus, the change of the resistivity in the study area is more affected by the salinity of the water contented in the stratum.
3. The local lower resistivity zones at a depth less than 30 meters were caused by lagoon environment around the Wenchang and Maachourhow areas. Most of the region in the coastal plain were in the shore depositional environment and affected greatly by the paleo-transgression and regression.
4. The potentials of aquifers in the northern part of the survey area are better than that in the south. The aquifers in the western part contain more saline water and show lower resistivity than other areas.
5. The changes of resistivity distribution at different depth in the Chiayi and Tainan areas indicate that the landward Tainan transgression once reached to around Suanntou, Luhtsao, Shinyng, Shiahyng and western part of Guantyan areas. However, the Dahhwu transgression can not recognized by this study.
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