贵阳地区下三叠统安顺组遗迹化石及古环境意义

贵阳地区下三叠统安顺组中的遗迹化石是研究P-T生物大灭绝后古环境、古生态的良好材料，在研究区发现、描述了8个遗迹属，9个遗迹种。安顺组中遗迹化石的垂向分布表明:安顺组一段以结构单一、个体较小的遗迹化石Planolites montanus，Palaeophycus curvatus和Phycodes palmatus为主；二、三段中遗迹化石属种增多、生物扰动增强，除了一段的3个遗迹种外还发现有6个遗迹种:Beaconichnus darwinum，Chondrites recurvus， Thalassinoides paradoxicus，Thalassinoides horizontalis，Arenicolites isp.，Rhizocorallium commune，在三段出现的复杂遗迹化石Rhizocorallium commune和Thalassinoides paradoxicus代表了本地区海洋环境在早三叠世晚期的重大改善。岩性特征和生物化石特征表明安顺组一段上部为台缘浅滩环境，二段为碳酸盐岩台地边缘斜坡环境，三段为靠近台地边缘的潮间-潮下环境，在一至三段沉积期，海水含氧条件有所改善，研究区处于浅海“宜居带”上。安顺组四段沉积于半局限台地内的潮间-潮上环境，处于“宜居带”之外，在此区域遗迹化石不发育，生物活动相对较弱。早三叠世奥伦尼克期遗迹化石发育特征表明生物复苏活动在碳酸盐岩台地边缘带相对活跃。

Trace Fossils and Their Paleoenvironmental Significance of the Early Triassic Anshun Formation in Huaxi Area,Guiyang

The trace fossils in Guiyang area was a good proxy for ecosystem recovery after the end-Permian biotic crisis. A total of 8 ichnogenera and 9 ichnospecies were identified in the Anshun Formation(including four members,A1,A2,A3,A4), their vertical distribution and evolution indicate that:trace fossils were dominated by small, simple, horizontal burrows of Planolites montanus, Palaeophycus curvatus and Phycodes palmatus in A1; Trace fossils become more abundant and diverse, and bioturbation index increased in A2 and A3. In addition to the 3 ichnospecies ichnogenera noted in A1, 6 other ichnospecies were abundant in these two members:Beaconichnus darwinum, Chondrites recurvus, Thalassinoides paradoxicus, Thalassinoides horizontalis, Arenicolites isp., Rhizocorallium commune. Complex fauna with Rhizocorallium and Thalassinoides in A3 represented a significant improvement in the marine environment in the late Early Triassic. No trace fossils were found in A4. The sedimentary environment from A1 to A3 occur in platform margin shoal to platform slope to tidal to supratidal zone, respectively. During A1 to A3, the oxygen conditions of marine environment had ameliorated. This condition could provide an optimal zone for benthic colonization. The characteristics of the trace fossils from upper A1 to A3 indicated that the study area came into the habitable zone environment. A4 was deposited in the semi restricted platform, and in the region above the habitable zone that the biological activity is relatively weak. The study of trace fossils suggested marine benthic recovery system was relatively active in the carbonate platform margin.