從惠來遺址出土遺物和古土壤形態探討台中盆地史前環境

A Reconsideration to the Paleo-Environment of the Taichung Basin Based on the Artifacts and Morphologies of Paleosols at the Hui-Lai Site

本研究在台中市西屯區惠來遺址南側惠民段145號地的調查顯示，主要有牛罵頭與番仔園文化層，出土遺物以陶器、石器等為主。其次出土的生態遺物以低海拔次生林植物為主，顯示當時地表環境受到人類活動的影響，此外還發現碳化稉稻代表番仔園時期有耕作活動。另外在碳十四定年分析與土壤層的觀察上，THL-1剖面的碳十四年代距今1070~920年前，土壤質地為偏砂質地，具豐富的有機物。而THL-2可觀察到兩個文化層，其中番仔園文化層中的碳十四年代顯示，距今約1300-1170年前，與THL-1同期或是略早形成。由於牛罵頭文化層和番仔園文化層，兩層土色均偏黃到暗棕色，顯示在兩文化層形成時期，地表面應相對穩定，使得土壤得以化育。基於此應可合理推論台中盆地在千年前，至少在本研究區涵蓋的範圍內，應非湖泊或海灣的環境，當時牛罵頭文化的史前人群，即生活在辮狀河系發達的氾濫平原上。

In the 1970s, exploration and trial excavations in Pakua and the Tatu Tablelands under the archaeological investigations in the Choshui and Tatu River Valleys of West-Central Taiwan led to the significant geological finding that the Taichung Basin was once a lake. According to the decoration pattern of potsherds and carbon-14 datings, the prehistoric culture in Central Taiwan can be classified into four stages, i.e., the Ta-peng-ken, Niumatou, Yinpu and Fantziyuan cultural layers. In this study, the Niumatou and Fantziyuan culture assemblages were unearthed from 145, Hui-lai site. Two test pits of paleosol samples (THL-1 and THL-2) were collected for further analysis. The THL-1 morphologies, characterized by their dark color, abundant organisms, and ＞30% clay contents, indicate that the sedimentary environment was a wetland between channels. The C14 age of the THL-1 has been determined as about 1070 BP. The 2A-2Bw sequence of THL-2 (C14 age 1300-1170 BP) belonging to the Fantziyuan culture assemblages showed a yellowish color and few clay morphologies, whereas the 3A-3Bw sequence of THL-2 belonging to the Niumatou culture assemblages revealed morphologies of brown-yellowish color, higher clay contents (＞30%) and weak sub-angular block structure. This suggests that prehistoic people in the Niumatou and Fantziyuan cultural periods lived on a stable landform surface that resulted in soil development. Based on the correlations between the pedologic morphologies of THL-1 and THL-2, people of the Fantziyuan culture assemblages selected sites close to a wetland between channels in the braided plain of the Taichung Basin. Therefore the hypothesis that the Taichung Basin was a lake during late Holocene could be unreasonable.