THE STRATIGRAPHIC DIVISION AND CORRELATION OF THE SURFICIAL QUATERNARY DEPOSITS IN THE HUIROU AREA, BEIJING

For the first time the surficial Quaternary deposits in the Huirou axea. Beijing, are divided from older to younger into the following five stratigraphic units; Middle Pleistocene, Upper Pleistocene, Lower Holocene, Middle Holocene and Upper Holocene. （1） The Middle Pleistocene: it consists mainly of slope-wash and diluvial deposits, 8 m thick; its lower part is marked by alternating beds of light red breccias and mild clays, while its upper part red and yellowish red angular fragment-bearing mild clays. （2） The Upper Pleistocene: its lower part consists of diluvial gravels with mild clays, 11.8 m thick, with thermoluminescent ages of 71±3.6 Ka and 66± 3.2 Ka;its middle and uppei parts are made up of alluvial mild clays and fine sands with several peat beds, 8.9 m thick, yielding mollusk fossils, with a thermolu minescent age of 27±1.4 Ka and C¹⁴ ages of 19.3-15.4Ka. The Holocene may be divided into three paits. （3）The Lower Holocene: it is composed of alluvial fine sands with gravels, 4-6 m thick, and locally represented by sandy clays and clays, 2 m thick, in which the peat interbeds were measured to have C¹⁴ ages of 9.291±0.161 Ka and 6.750±0.128 Ka. （4） Middle Holocene: it is marked by mild clays in the upper, black peat beds in the middle and fine sands and gravels in the lower, 5.1m thick, with C¹⁴ ages of 4.730-2.976 Ka. （5）The Upper Holocone consists of alluvial fine sands and gravels, varying in thickness from place to place, having a C¹⁴ age of 8.64±0.131 Ka.