Late Cretaceous palynology and paleoclimate change: Evidence from the SK1 (South) core, Songliao Basin, NE China

Abstract

Cretaceous climate was warmer than today. The Songliao Basin contains one of the most important Late Cretaceous non-marine deposits in China for the research of the paleoenvironment and paleoclimate. This research is based on core samples from the SK1(S) borehole. The strata sampled are the upper part of the Quantou Formation to member 2 of the Nenjiang Formation, where spores, pollen, dinoflagellates, and other microfossils are abundantly preserved. Based on analysis of the spores and pollen fossils from the core samples, the following six fossil assemblage zones have been recognized in ascending order: The . The six fossil zones range from the late Cenomanian to early Campanian. The Late Cretaceous dinoflagellate cysts in the Songliao Basin are of high abundance and low diversity. Specific phytoplankton types reflect salinity changes of the Songliao Lake. Paleoecology of the dinoflagellates suggests that sediments of members 2 and 3 of the Yaojia Formation (K 2 y 2+3 ) were deposited in a freshwater environment, whereas members 2 and 3 of the Qingshankou Formation (K 2 q 2+3 ) and members 1 and 2 of the Nenjiang Formation (K 2 n 1+2 ) were deposited in freshwater to brackish water environments. Combined with the paleoecology of dinoflagellates and the palynomorph biozones, valuable information of the paleoclimate was provided. The quantitative analyses of spores and pollen fossils, such as vegetation type, climate type, and humidity type, diversity and dominance, indicate a relatively sub-humid, mid-subtropical paleoclimate, with slight climatic fluctuation and/or temporal change.Late Cretaceous, Songliao Basin, spores and pollen, dinoflagellate, paleoclimate Citation:Zhao J, Wan X Q, Xi D P, et al. 2014. Late Cretaceous palynology and paleoclimate change: Evidence from the SK1 (South) core,

Late Turonian Microfossils and Paleoclimate in the Songliao Basin, NE China

“…The global paleoclimate was suggested to hot during this period [2]. Based on the core of SK1(s) from the Songliao Basin, a detailed study of spore and pollen suggested a relatively warm and wet climate during Late Turonian [5], which is consistent with our results. Dur-…”

“…Open Journal of Geology still not well understood. The Well-preserved Cretaceous lacustrine deposits in this basin provide a unique opportunity to study terrestrial paleoenvironments and paleoclimate during the Late Cretaceous [4] [5]. Here, the microfossils from the Late Turonian Qingshankou Formation of the Songliao Basin were used to study the paleoenvironments and paleoclimate of East Asia.…”

Compound-specific carbon isotope study on the hydrocarbon biomarkers in lacustrine source rocks from Songliao Basin

“…4), which may be related to massive freshwater input in a short time (unpublished hydrogen isotopic data) (Zhao et al, 2014). Relative to the C 28 and C 29 4a-methyl steranes, the C 30 4a-methyl sterane is clearly enriched in 13 C, which may reflect the variation in water salinity.…”

“…Thus, the massive black shale sedimentation during the Cretaceous period is also associated with the high productivity of the ocean rather than the anoxic event itself. Previous evidence from algae fossils and biomarkers have shown that there was high lacustrine productivity during the depositional period of K 2 n 1 and K 2 n 2 (Yang et al, 1981;Feng et al, 2009;Zhang and Bao, 2009;Xi et al, 2012;Wang et al, 2013;Zhao et al, 2014), but they show obviously different OM abundances. The OM content is high under the anoxic condition in K 2 n 1 , but the OM abundance declines rapidly during K 2 n 2 with its oxic environment, which suggests that even under the condition of high productivity, it still difficult to form a high OM deposit if there is not a good preservation environment for the OM.…”

Paleoenvironmental reconstruction of the Late Santonian Songliao Paleo-lake

“…An increasing number of studies suggest that the formation of a hydrocarbon source rock in K 2 n 1+2 of the SLB relates to the marine transgression (Hou et al, 2000;Xi et al, 2011a;Huang et al, 2013;Hu et al, 2015). While paleontologic data indicates (Gu and Yu, 1999;Sha, 2007;Wan et al, 2013;Ye et al, 2002;Zhao et al, 2014) changes in lake water salinity during the Late Coniacian to early Campanian (Table 1), the exact reason for the formation of the massive hydrocarbon source rock in K 2 n 1 + 2 is still unknown (Li and Pang, 2004). The specific environmental changes that took place within the paleo-lake resulting from seawater incursions during the marine transgression in K 2 n 1 + 2 remain unclear.…”