关键词: 堆积层;盘县大洞

Abstract: The records of local history and oral account of local people show that the sediments inside Dadong cave have been greatly disturbed by local people for various reasons in the past 100 years. The g rand main hall o f the cave measures 250m from its back w all to the entrance and covers a n area o f roughly 9900m2 . The deposit is estimated to be 19. 5m thick near the entrance. The middle and low er part of the sequence are generally preserved. Therefore, comparing with the g rand scale and the preserved portion of the deposit, the man-made disturbance of Dadong is limited.
The sediments inside the cave consist of two parts in source. One comes from the cave itself, which includes blocks and fragments of limestone, travertine. The other includes clay, sand, gravel, fragments of limestone which were brought from the hill slope outside cave by g round water and loess-like clay which may be brought into cave by wind. In addition, animal and human fossils, stone artefacts, evidences of using fire ( ash, charcoal, burnt bones) and etc. are in relation with human activities mainly. According to composite analysis, the sediments above-mentioned have no direct relation to river. In other words, they have been deposited within the cave after the cave separated itself from the under- ground river.
Preliminary observation o n the exposure at the front area of main hall, the upper part o f sediments can be divided into 8 layers from to p to base as follow s:
Layer 1 The first travertine, 5— 10cm, slightly brow n. 130ka based on U-series dating.
Layer 2 Brow n sandy clay , powdered clay with breccia , 2. 5— 4m. Abundant animal fossils and cultural relics are present.
Layer 3 The second travertine, 5— 12cm, greyish brow n. Stone artefacts, charcoal and animal fossils a re present. 200ka based on U-series da ting.
Layer 4 Greyish brow n sandy clay , clay with breccia, 1— 2. 5m. Abundant stone artefacts and animal fossils, as w ell as charcoal are present.
Layer 5 The third travertine, 10— 25cm, g reyish brow n. 260ka based o n U-series dating.
Layer 6 Brow n sandy clay with breccia, 0. 5— 1m. Abundant stone artefacts and animal fossils, as well as charcoal and burnt bones are present.
Layer 7 The fourth travertine, slightly brow n, 5— 10cm.
Layer 8 Brow n sand with bedded clay , as w ell as breccia, fragments o f fossil and some blocks of limestone, 1. 8m.

Key words: Depositional sequence, Panxian Dadong