Kayitou Fm
Type Locality and Naming
Type section at Kayitou, west of Dasuopo, Rongfeng County (old Xuanwei County), Yunnan Province. Named by Wang C C, Huo S C, 1945, Geology of Houso Coal Field, Pingyi, Yunnan, Bull. Geol. Surv. China, (36): 27.
Synonym: Kayitou Shale Fm, Kayitou Yellowish Green Shale and Sandstone Beds.
Lithology and Thickness
"Lower part is olive/grey/black mudstone, siltstone, fine to coarse sandstone. Followed by gradually increasing maroon rocks, to purely maroon mudrocks. This formation is defined by the last appearance of coal seam at the base and last appearance of olive/grey rock at the top. Therefore, there is no coal in this formation. Poorly-sorted breccia and palaeosol with calcareous nodules occur in the upper part of the formation. It is 10.1 m thick at the Guanbachong section, 24.5 m thick at the Chahe section, 9.4 m at the Lubei section, and 6.4 m thick at the Longmendong section " (Zhang et al., 2016).
Relationships and Distribution
Lower contact
Overlies the highest coal in the Xuanwei Fm of late Permian.
Upper contact
Overlain by the Dongchuan Fm of early Induan. "Specifically, the topmost part of the Kayitou Formation at the Guanbachong section is marked by a 1.6-m-thick coarse volcanogenic sandstone with calcareous sandy nodules, abundant charcoal fossils, and malachite spots on the bedding plane. It is marked by a poorly-sorted lacustrine breccia with conchostracans, charcoal fossils, and malachite spots at the Longmendong section. The boundary between the Kayitou Fm and the Dongchuan Fm at the Chahe and Lubei sections is transitional, syngeneric calcareous sandstone nodules begin to occur in the upper part of the Kayitou Formation, and numerous calcareous nodules occur in the basal part of the Dongchuan Fm. The overlying Early Triassic Dongchuan Formation is characterized by uniformly maroon fine to medium sandstone, siltstone, and mudstone with trough cross-bedding, parallel bedding, and scour structures. " (Zhang et al., 2016)
Regional extent
East Yunnan.
GeoJSON
Fossils
"Our analyses show that the transitional Kayitou Formation actually recorded the process of terrestrial mass extinction as evidenced by the mass disappearance of the Gigantopteris megaflora in the lower part, the dramatic reduction in abundance of palynomorphs in the middle, and the last occurrences of plant remains and abundant charcoal fossils in the uppermost part. It is associatedwith a distinct negative shift of δ13Corg, beginning in the middle part of the formation, which is correlative with that in the top of Bed 26 at the marine Meishan section. … The Kayitou Formation contains many elements of the Permian Gigantopteris flora in the lower part (e.g., Gigantopteris, Lobatannularia, Stigmaria, Taeniopteris etc.) and occasionally with some marine fossils such as the brachiopod Lingula spp., the ammonoid ophiceratids and monotonous, but highly abundant bivalves such as Pteria ussurica variabilis, Eumorphotis multiformis, and the ostracod Langdaia subolonga etc., abundant conchostracans Euestheria and Palaeolimnadia, and the “Triassic-type” plant fossil Annalepis in some sections of coastal setting " (Zhang et al., 2015)
Age
Depositional setting
"The Kayitou Formation is characterized by a distinct shift of lithofacies of fresh lake-swamp or river flat environment from olive/grey/black mudstone, siltstone, fine to coarse sandstone in the lower part to gradually increasing maroon rocks, to purely maroon mudrocks with poorly-sorted breccia, calcic palaeosols and calcareous nodules in the lowest part of the Dongchuan Fm, which indicates a dramatic collapse of soil system associated with rapid deforestation and climaticwarming and drying. In the coastal area, the Kayitou Formation contains marine beds with the typical Permian–Triassic mixed faunas and floras which are correlative with the latest Changhsingian marine mixed fauna 1 at Meishan. The Kayitou Formation also recorded a distinct transgression that began in the latest Changhsingian." (Zhang et al., 2016)
Additional Information