The Biogenic Structures In Carbonate From The Third Member Of The Mantou Formation(Cambrian Series 3), Dengfeng Area, Western Henan

The Third Member of the Mantou Formation(Cambrian Series 3) exposed superbly in western Henan Province with abundant carbonate and biogenic structures. Based on the characteristics of petrology, sedimentology and ichnology from the carbonate.The Detailed analysis of the oolitic limestones, pellet calcarenite, and flat-pebble limestones from the Third Member of the Mantou Formation. Especially to contion oolitic limestone, pellet calcarenite of biogenic structure and biogenic structures from them were detailed analysis in the macroscopic, microscopic characteristics. The following conclusions:(1)A large amounts of vertical burrows developed in the pellet calcarenite from the lower part of the Mantou Formation.There are at least 4 ichnogenus and 8 ichnospecies, namely, Skolithos verticalis, Skolithos linearis, Arenicolites ichnosp.1, Arenicolites ichnosp.2, Diplocraterion ichnosp.1, Diplocraterion ichnosp.2, Diplocrater-ion ichnosp.3, Monocraterion ichnosp. A bundant vertical or near vertical burrows by filter-feeding animals occurred in the oolitic limestones from the lower part of Third Member of the Mantou Formation. The Skolithos is the most abundant,the other is Arenicolites.(2)A suit of carbonate storm deposits with a large amounts of biogenic structures are found in the lower part of the Third Member of the Mantou Formation.The storm deposits in strong stage, weakening stage and quiet stage are respectively composed of flat-pebble limestones with stromatolites around, oolitic limestones with vertical burrowsand stromatolite limestones.There are various forms of stromatolites growed around the flat-pebble limestones. Oolitic limestones with vertical burrows are characterized by spherical, ellipsoidal radial and concentric-radial ooids and microcrystalline and microsparite calcite cements among ooids and are formed in low to medium energy deep platform slope near the normal wave base. The stromatolite limestones are generally thin and characterized by small columnar stromatolites. Amount of clay and a few ooids and bioclasts are filled among columnar stromatolites.(3)Three storm sedimentary successions are recognized in study area. The succession 1 consists of scoured bases, flat-pebble limestone beds and various cross-beddings and reflects the in situ storm deposits formed in strong stage and weakening stage. The succession 2 is dominated by scoured bases, flat-pebble limestone beds and mudstone?marl and represents the proximal storm deposits formed in strong stage and quiet stage. The succession 3 is characterized by scoured bases, various cross-beddings and stromatolite limestone beds and displays the distal storm deposits formed in weakening stage and quiet stage. The above storm deposits are the multiphase incomplete storm records at different storm processes.