A possible causal relationship between extinction of dinosaurs and K/T iridium enrichment in the Nanxiong Basin, South China: evidence from dinosaur eggshells

Geochemical environmental changes and dinosaur extinction during the Cretaceous-Paleogene (K/T) transition in the Nanxiong Basin, South China: Evidence from dinosaur eggshells

“…Obviously, each oospecies has a small variation in eggshell thickness. The average values of eggshell thickness in each oospecies at various levels show almost no change, and represent the normal range of predominating variation (see Figure 6(a) published in Zhao et al [14] ).…”

“…The eggshell thickness of Macroolithus yaotunensis ranges from 0.9 to 2.36 mm, that of Macroolithus rugustus from 0.92 to1.96 mm, that of Elongatoolithus andrewsi from 0.6 to 1.52 mm, and that of Elongatoolithus elongatus from 0.6 to 1. and CGT-CGF sections (see Figure 6(b), (c) published in Zhao et al [14] ). light microscope and the scanning electron microscope shows that many of them have various histopathological patterns such as a bi-or multi-layered cone and disorderly arranged crystallines, and irregular or dendritic spaces in the columnar layer of the eggshell (Figure 4(b), (c), (d)).…”

“…According to Zhao et al [14] , in the CGH Section of the Yuanpu Formation the eggshell thickness of Macroolithus yaotunensis range between 1.70 and 2.52 mm, those of Macroolithus rugustus between 1.66 and 2.38 mm, those of Elongatoolithus andrewsi between 1.36 and 1.58 mm, and Elongatoolithus elongatus between 0.9 and 1.26 mm. Obviously, each oospecies has a small variation in eggshell thickness.…”

“…at the K/T boundary interval, as discussed later), the frequency increases to 50% to 85% ( Table 2). This is one more proof that anomalous concentrations of trace elements including Ir are associated with the formation of pathological eggshells [10,11,14,18] . The enrichment of Ir and other trace elements in the eggshells may have been caused by the assimilation of these elements into the dinosaur body through food (mechanisms discussed in Zhao [18] ; Zhao et al [10,14] ; Yang et al [17] ).…”

“…Previously published data [10][11][12][13][14][15][16] from the CGY-CGD and CGT-CGF sections ( Figure 1) showed that the geochemical environmental changes and the dinosaur extinction in South China may have been a rather long-ARTICLES GEOLOGY duration process rather than an instantaneous event that only lasted a few years or centuries as is often portrayed in the asteroid hypothesis. To obtain a better idea on how the cause and timing of the dinosaur extinction took place, we have investigated trace elements including Ir, stable isotope composition, and eggshell structures in a series of dinosaur eggshells from the third K/T section (the CGN section) in this basin.…”