CRETACEOUS TERRESTRIAL BIOTA AND LAKE ENVIRONMENT IN NE CHINA

Northeast China is the type locality of nonmarine Cretaceous, offers a unique opportunity to perceive Cretaceous stratigraphy and climate of terrestrial settings. The sediments contain variegated clastic and volcanic rocks, diverse terrestrial fossils, and important coal and oil resources. Four Cretaceous biotas of Jehol, Fuxin, Songhuajiang and Jiayin have been recognized. The Jehol Biota is famous for feathered dinosaurs, early birds and angiosperm; The Fuxin Biota coexists with the Fuxin Coal Mine and dominated by abundant plant and bivalve fossils; The Sonhuajiang biota contains the dominant fossils of ostracods, charophytes, spore and pollen, and foraminifera as well; The Jiayin biota is represented by latest Cretaceous dinosaurs and other fossils. Stratigraphically, the Jehol biota belongs to Valanginian to lower Aptian; Fuxin biota upper Aptian to Albian; Songhuajiang biota Cenomanian to lower Campanian; and Jiayin biota upper Campanian to Maastrichtian.

For scientific purpose, a coring program (SK1) provides significant material for Upper Cretaceous research. Based on detailed biostratigraphy, high-resolution magnetostratigraphy and SIMS U-Pb zircon analyses, the SK1 core is correlated with the international Upper Cretaceous stages, and the K/Pg boundary is likely within the uppermost part of the Mingshui Formation. Terrestrial life show that lake water salinity changed in a freshwater –brackish water –freshwater cycle, along with a Coniacian-Santonian marine incursion. Lake-level fluctuations resulted in the development of periodic anoxic environments in the deepest parts of the basin. One of these times of deposition of organic-rich mud correlates with the mangnetochron of C34N/C33R and Coniacian-Santonian planktic foraminifera. This marine flooding correlates with OAE 3 and it is possible that the global oceanic anoxic event may have influenced organic carbon burial in the Songliao Basin for this brief period.

Four biotas in NE China correspond to the Cretaceous climate change. We tentatively interpret this record to reflect the changes in both global climate and regional basin evolution.