Jehol fossils from the Jiaolai Basin of Shandong, North China: review and new perspectives

Starting in the early 1950s, paleontologists began to discover a wide range of Cretaceous terrestrial fossils in the Laiyang, Qingshan, and Wangshi groups of the Jiaolai Basin which resides in the eastern part of the Shandong Peninsula of northern China. Significant specimens from these deposits include various dinosaur eggs, footprints, and fossils including hadrosauroids, tyrannosaurids, and ankylosaurids. These expanded understanding of evolution, biodiversity, and paleoecology in East Asia. While many examples of the Jehol Biota from this area are not well constrained in terms of their stratigraphy and geochronology, previous studies have generally suggested that fossils from this region represent the second or third phase of Jehol Biota development. This paper reviews fossils, stratigraphic correlations, tectonic history, and age estimates for the less well-studied outcrops of the Shandong Peninsula that host Jehol Biota. We report three new 40Ar/39Ar ages for the Qingshang Group and discuss how these somewhat imprecise ages still constrain chronostratigraphic interpretation for the fossil-rich units.

Surface Chlorophyll-A Fronts in the Yellow and Bohai Seas Based on Satellite Data

Chlorophyll fronts are important to monitor and map the oceanic front, especially in the season when sea surface temperature (SST) fronts weaken. In this study, surface chlorophyll-a (chl-a) fronts in the Yellow and Bohai seas were characterized for the first time using satellite data. Five distinct chl-a fronts (i.e., the Bohai Strait, Shandong Peninsula, Jiangsu, Liaodong Peninsula, and Korean Peninsula fronts) were observed in summer along the 40 m isobaths and faded in other seasons. Notably, these fronts coincided with SST fronts. Strong chl-a fronts emerged during summer due to chl-a blooms in eutrophic coastal waters paired with surface chl-a fading in strongly stratified offshore waters and coastal physical fronts. Although SST fronts were strong during winter, light limitation and strong vertical mixing in offshore waters led to low chl-a in both coastal and offshore waters, suppressing chl-a front formation. Both chl-a and SST fronts coincided with steep seabed slopes (slope ratio > 1), suggesting that seabed slope may be an indicator of oceanic front location.