山东即墨地区恐龙化石埋藏时代

The Burial Age of Dinosaur Fossils in Jimo Area in Shandong Province

摘要:

山东省即墨地区新发现原地埋藏的恐龙化石，其埋藏与火山活动密切相关。为了确定化石层的埋藏时代，进行了火山岩单颗粒锆石SHRIMP UPb定年，获得的即墨地区恐龙化石层下伏的安山质集块角砾凝灰岩中最年轻锆石年龄为（121.8±1.8）Ma，上覆的辉石安山岩加权平均年龄为（117.5±2.2）Ma，限定了新基干鸟脚龙化石埋藏时代为117.5～121.8 Ma，属于阿尔必期，与胶莱盆地多地发现的鹦鹉嘴龙生存时代同期或者更早。另外，在火山岩中发现较多捕获锆石，年龄值集中在126.5～139.5 Ma和2 548～2 727 Ma之间，还有1 810 Ma、2 014 Ma、763 Ma、800 Ma、140.5 Ma、141.6 Ma等，反映了胶莱盆地沉积之前的基底与胶北隆起区构造—岩浆事件相吻合，说明即墨地区中生代地层是叠加在与胶北隆起具有相同性质的基底断陷之上的陆相盆地沉积。

Abstract:

The newly discovered dinosaur fossils buried in Jimo area in Shandong province are closely related to volcanic activity. In order to determine the burial age of the fossil layers, SHRIMP UPb dating of he single grain zircon in volcanic rocks has been carried out. The youngest zircon age of the andesitic agglomerate breccia tuff under the dinosaur fossil layer in Jimo area is (121.8±1.8)Ma, and the weighted average age of the overlying pyroxene andesite is (117.5±2.2)Ma. It has limited the burial age of the ornithopod dinosaur to 117.5~121.8Ma. It belongs to Albian period and is the same as or earlier than the survival age of Psittacosaurus found in many places in Jiaolai basin. In addition, many captured zircons have been found in volcanic rocks, and the ages data have been concentrated between 126.5~139.5 Ma and 2548~2727 Ma, as well as 1810 Ma, 2014 Ma, 763 Ma, 800 Ma, 140.5 Ma, 141.6 Ma and other data. It is reflected that the basement before the deposition of Jiaolai basin is consistent with tectonicmagma events in Jiaobei uplift area. It is showed that Mesozoic strata in Jimo area are continental basin deposits superimposed on the basement fault depression with the same properties as Jiaobei uplift.