黄土高原一个连续的晚新生代剖面及其划分与对比

陕西旬邑地区一个地层厚约 2 30 m的晚新生代剖面 ,全为土状堆积。岩性划分、古地磁测年、古生物研究及其他一些手段的分析测定表明 ,该剖面记录了距今 6 .8Ma到现代的沉积 ,其中第四系厚 141.2 m,全为黄土—古土壤沉积序列 ;新近系厚约 90 m,全为红土沉积 ,底部不整合面之上有 6— 7m红土层被覆盖 ,无法取样 ,其上实测厚度83.4m,将每层红土层及紧接其下的钙质结核层称为一个成土—成壤组合 ,新近系约含 80个明显的成土—成壤组合。 N/Q岩性界线在剖面深度的 141.2 m处 ,但古地磁 M/G界线在相当于剖面深度的 137.6 m处 ,即 L43 顶界之上0 .4m处 ,古地磁极性的转移滞后于岩性的变化。多层生物化石的发现对各段地层时代的确定及古气候环境的分析起了积极的作用

SUBDIVISION AND CORRELATION OF A NEARLY CONTINUOUS LATE CENOZOIC PROFILE IN LOESS PLATEAU

A nearly continuous Late Cenozoic profile has been discovered near the Xiaqiang village, Xunyi County, Shaanxi Province. It is about 232m thick in total, overlying unconformably the Mesozoic inclined strata. It is composed of two Systems and four Series:the Upper Miocene and Pliocene of Neogene and the Lower, Middle, and Upper Pleistocene and Holocene of Quaternary. Both systems in this area are earthy sediments without coarse clastic rocks, which is their most obvious common feature. There are 43 layers of loess interbedded with paleosol in Quaternary System; and more than 80 layers of red clayey fine siltite interbedded with lime nodule in the Neogene System. For the convenience of description and correlation, these layers would be grouped into about 20 bed groups.