本研究應用直流電阻法，將野外收集的461個地電測點資料，參考井地層柱資料，進行一維逆推處理，對台灣西南海岸平原從北港溪至二仁溪間作電性地層研究。根據地層的電阻率和厚度分析，可將本區深度200公尺以內的地層歸類成三個電性地層單位，分別稱為Ｔ相、Ｓ相和Ｒ相。Ｔ相除少數表層出現100歐姆米以上的高電阻之外，電阻率介於10至70歐姆米之間，厚度則在1到90公尺之間，主要出現在測區的中部和東部，以陸相、河口與潟湖沈積環境為主。Ｓ相電阻率在8歐姆米以下，厚度範圍從35公尺到超過120公尺，主要出現在測區西部，但多由薄層的Ｔ相所覆蓋，以濱海相沈積環境為主。Ｒ相電阻率範圍介於3到90歐姆米之間，在測區東部為Ｔ相地層所覆蓋，在西部則為Ｓ相覆蓋，在測區南部鹽水溪到二仁溪間的地區，受到地層解析度的影響，Ｓ相深部可能含有Ｒ相，但無法將其區分出來，本相主要以陸相及河口沈積環境為主。根據井定年資料顯示，Ｔ和Ｓ相為全新世地層，Ｒ相為晚更新世地層，Ｒ與Ｔ或Ｓ相的界限即代表晚更新世與全新世地層的界限，此界限深度範圍介於海平面以下10到130公尺之間，大體上呈現由東北方往西南方逐漸加深，在鹽水溪到二仁溪之間則無法得知此界限的深度。 Geoelectric surveys at 461 VES locations were carry out in the area of the coastal plain between Peikangchi and Erhienchi, southwestern Taiwan. The sounding data were interpreted by using 1-D inversion method. The electrostratigraphy in the study area can be obtained. Based on the resistivity and thickness of the layers derived from the sounding data, three electrostratigraphic units are being recognized. From the ground surface to a depth of 200 m, the strata were named the T, S, and R facies. The resistivity of T-facies is ranging from 10 to 50 ohm-m with a thickness of 1 to 90 m. It locates in the center and east of the study area and associated with the terrestrial, estuarine and lagoonal environments. The resistivity of S-facies is less than 8 ohm-m. it has a thickness ranged from 35 to 120 m or more. Most of S-facies are overlaid by the T-facies in the western part. It may associate with a marine environment. The resistivity of R-facies is ranging from 3 to 90 ohm-m. It is overlaid by the T-facies in the eastern part and by the S-facies in the western part of the study area. In the southern part of the study area (between Yanshuichi and Erhjenchi), the S-facies and R-facies may merge together in a great depth. But we can’t prove it by a limited depth penetrating of this survey. The R-facies may deposite in the terrestrial and estuarine environments. Based on the dating results obtained from well samples, the T and R-facies were deposited in Holocene, and the R-facies was deposited in late Pleistocene. The boundry between R and T-facies or R and S-facies may associate with geological boundary between late Pleistocene and Holocene. The depth of the boundary is ranging from 10 to 130 m below the sea level, it has a trend of increase the depth from northeastern to southwestern. However, the boundary between Yanshuichi and Erhjenchi is still uncertainty from our data.
