浙江义乌上白垩统金华组滨湖相红层中的遗迹化石

ICHNOFOSSILS FROM THE LACUSTRINE RED BEDS OF THE UPPER CRETACEOUS JINHUA FORMATION IN YIWU,ZHEJIANG,EAST CHINA

浙江金衢盆地上白垩统金华组湖相红层总厚度超过2000m,义乌观音塘剖面金华组薄—中层红色粉砂岩和泥岩出露厚度约20 m,层面上保存的波痕、泥裂等沉积构造指示当时该地区是湖底经常暴露的滨湖地带。实体化石稀少,仅见少量植物化石碎片,但粉砂、黏土沉积时因含水可塑性,记录了大量脊椎动物和无脊椎动物的活动遗迹。本文首次报道其中无脊椎动物形成的遗迹化石,包括Arenicolitesisp.(沙蠾迹未定种)、Skolithos magnus(大石针迹)、Skolithos isp.(石针迹未定种)、Scoyenia isp.(斯科茵迹未定种)、Thalassinoides isp.(海生迹未定种)、Cochlichnus anguineus(蛇形螺丝迹)、Palaeophycus isp.(古藻迹未定种)、Planolites beverleyensis(贝利弗漫游迹)、Helminthopsis isp.(拟蠕形迹未定种)和Circulichnis isp.(圆环迹未定种)。遗迹化石多样性指示滨湖区动物活动频繁,形成复杂生态系统。

The lacustrine red beds of the Upper Cretaceous Jinhua Formation with a maximum thickness of more than 2000 m were deposited in the Jin-Qu Basin of Zhejiang Province,East China.A part of the Jinhua Formation measured about 20 m in thickness is outcropped at the Guanyintang section,Yiwu is composed of thin-medium bedded red siltstones and mudstones.Sedimentary structures are rich in rippers and mud cracks due to the instant exposure of the lake floor herein during the deposition of these strata.Body fossils are extremely low in abundance except sparse plant fragments from the Guanyintang section.However,abundant ichnofossils made by vertebrate and invertebrate animals are preserved in the red beds due to aqueous plasticity of the silty and muddy sediments.Ichnofossils made by invertebrates are firstly documented in the present paper including Arenicolites isp.,Skolithos magnus,Skolithos isp.,Scoyenia isp.,Thalassinoides isp.,Cochlichnus anguineus,Palaeophycus isp.,Planolites beverleyensis,Helminthopsis isp.,and Circulichnis isp.Their biodiversity suggests that the animals were active,and a complex ecosystem was potentially existed in the lake-shoal belt.