The species diversity of fusulinaceans and high-frequency sea-level changes in the Carboniferous-Permian boundary section at Xikou, Zhen’an County, Shaanxi Province, China

Abstract

The study on the interrelation between sea-level changes and biodiversity with its evolution has great significance for understanding the impact of global changes on organic evolution and exploring the inherent laws of life-environment coevolution in geological history. In this paper, the stratigraphic distribution of fusulinacean fauna in the Carboniferous-Permian boundary section at Xikou, Zhen'an County, Shaanxi Province, is analyzed quantitatively, and the relationship between the species diversity of fusulinaceans and relative sea-level changes is discussed. As a whole, the species numbers of fusulinacean fauna experience a rapid increase and an obvious decline in Xikou, Zhen'an County, from the Late Carboniferous to the Early Permian. There is a significant increase in species diversity around the Carboniferous-Permian boundary, which is one of the biggest bio-events of the fusulinacean fauna, and represents the radiation of Pseudoschwagerininae subfamily in the studied area. Integrated fusulinacean species diversity into sequence stratigraphic framework, detailed study suggests that the species diversity of the fusulinaceans is closely related to its relative stratigraphic location, and is essentially controlled by the sea-level changes, especially by the high-frequency sea-level changes. Generally, the species diversity of fusulinaceans is low, and the number of first and last appearance datum is small in the lower unit of high-frequency depositional cycle formed during the quick rise of the sea level; whereas the species diversity of fusulinaceans is high, and the number of first and last appearance datum is large in the upper unit of high-frequency cycle formed during the slow fall of the sea level. Within the third-order depositional sequence, the species diversity of the fusulinaceans at the first flooding surfaces and the maximum flooding surfaces is low, and it increases upward. The fusulinacean species diversity is low within the transgressive systems track, and it is high within the highstand systems track. The second-order rise and fall in sea level coincide with the bloom and decline of high order taxa of fusulinaceans.Fossil is a direct record of origin, development, decline, and extinction of living things. Utilizing fossil record to study biodiversity and its evolution in geological history is one of the basic goals of paleontology [1] . Since the last decades, the study on biodiversity and mass extinction has become an international "hot-spot" issue in paleontology field through establishing the global databases of marine invertebrate, drawing the curve of the biodiversity, and discovering the mass extinctions [2][3][4][5][6][7][8][9] . The Fusulinacea are a diverse group of Paleozoic foraminifera that evolved rapidly during the Carboniferous and Permian periods. The study of the diversity and its changes of fusulinaceans has great significance for understanding the evolution process and pattern of marine invertebrate in the late Paleozoic [4,10] . Recently, some researchers have established...

Root‐related rhodochrosite and concretionary siderite formation in oxygen‐deficient conditions induced by a ground‐water table rise

“…The distinctive dominance of odd over even C‐numbered n ‐alkanes indicates a higher plant origin (e.g. Peters et al ., ), while the prevailing n ‐C 29 suggests trees as the main source of organic matter (Zhang et al ., ) in the concretion‐bearing silt. The terrestrial Orava‐Nowy Targ basin experienced a warm and humid climate during the Mid Miocene Climatic Optimum (Oszast & Stuchlik, ; Böhme et al ., , ) which was favourable for the development of vegetation and for continental weathering supplying Mn and Fe.…”

“…Manganese and iron (oxy-)hydroxide precipitation often occurs around living roots in shallow oxic conditions (e.g. Sundby et al, 1998;Fimmen et al, 2008) and is particularly common in soils affected by seasonal aquic conditions leading to reduction, Zhang et al (2006). AI, Alkane Index, according to Zhang et al (2006).…”