ISOLATED olistoliths refer to massive blocks of rock occurring out of place, but with sedimentary contact relationship, within unrelated sediments. They were transported as single masses into the basins in which they ...ISOLATED olistoliths refer to massive blocks of rock occurring out of place, but with sedimentary contact relationship, within unrelated sediments. They were transported as single masses into the basins in which they occurred. In this note we will first report examples found from the Lower Triassic Xikou Formation in southwestern Fujian and discuss its geological significance.展开更多
Structural relationships between the Neoproterozoic rock complexes of a continental massif, island arc and back-arc basin geodynamic affinities are described and considered in this work based on field observations wit...Structural relationships between the Neoproterozoic rock complexes of a continental massif, island arc and back-arc basin geodynamic affinities are described and considered in this work based on field observations within the northeastern segment of the Central Taimyr tectonic zone distinguished in the late Hercynian fold- thrust belt of Taimyr Peninsula. As is established for the first time, rock complexes of the continental massif with the early Late Riphean （Tonian-Cryogenian） volcanogenic-sedimentary cover occur in the study region as the allochthonous syn- and post-sedimentary thrust sheets buried in or thrust over deposits of a back-arc basin, which accumulated in the terminal Late Riphean （Cryogcnian）-initial Vendian （Ediacaran）. These and other results of the large-scale structural observations elucidate important details of the region tectonic development in the Late Precambrian, when two lateral ensembles of the Neoproterozoic structures originated in the region. In the first half of the Neoproterozoic, the regional tectonic ensemble included the oceanic plate abut on the continental massif with a primitive volcano-plutonic belt. The subsequent system of an island arc and marginal back- arc basin originated in the second half of the Neoproterozoic and existed approximately till the mid-Vendian （Ediacaran） phase of the intense formation of thrust sheets in the region.展开更多
The Lower Triassic Xikou Formation in southwestern Fujian, China is a set of complex deep water sediments which includes turbidites, sandy contourites and isolated olistoliths. Five facies and seven subfacies are reco...The Lower Triassic Xikou Formation in southwestern Fujian, China is a set of complex deep water sediments which includes turbidites, sandy contourites and isolated olistoliths. Five facies and seven subfacies are recognized in the deep water turbidites, which are considered to belong to five facies associations of upper, middle and lower fans, respectively. The sandy contourites, which occur within turbidites as isolated thin layers with structures of traction current, are formed by reworking turbidites. They occur in discrete units, not as a part of a vertical sequence of structures, such as Bouma sequence. Paleocurrent directions derived from sandy contourites are perpendicular to or at a large angle of those derived from turbidites. In some areas, within the Formation there exist large oolitic limestone blocks slided from shallow sea. The temporal spatial distribution of three types of sediments mentioned above and the related evidences could indicate that a passive continental margin from shallow sea to bathyal abyssal region, dipping toward southeast, once occurred in study area during the early Triassic. The early Triassic represents a period of sea level uprising. The uprising of sea level and the development of isolated olistoliths probably imply gradual shrinking of an ocean basin at that time.展开更多
文摘ISOLATED olistoliths refer to massive blocks of rock occurring out of place, but with sedimentary contact relationship, within unrelated sediments. They were transported as single masses into the basins in which they occurred. In this note we will first report examples found from the Lower Triassic Xikou Formation in southwestern Fujian and discuss its geological significance.
文摘Structural relationships between the Neoproterozoic rock complexes of a continental massif, island arc and back-arc basin geodynamic affinities are described and considered in this work based on field observations within the northeastern segment of the Central Taimyr tectonic zone distinguished in the late Hercynian fold- thrust belt of Taimyr Peninsula. As is established for the first time, rock complexes of the continental massif with the early Late Riphean （Tonian-Cryogenian） volcanogenic-sedimentary cover occur in the study region as the allochthonous syn- and post-sedimentary thrust sheets buried in or thrust over deposits of a back-arc basin, which accumulated in the terminal Late Riphean （Cryogcnian）-initial Vendian （Ediacaran）. These and other results of the large-scale structural observations elucidate important details of the region tectonic development in the Late Precambrian, when two lateral ensembles of the Neoproterozoic structures originated in the region. In the first half of the Neoproterozoic, the regional tectonic ensemble included the oceanic plate abut on the continental massif with a primitive volcano-plutonic belt. The subsequent system of an island arc and marginal back- arc basin originated in the second half of the Neoproterozoic and existed approximately till the mid-Vendian （Ediacaran） phase of the intense formation of thrust sheets in the region.
文摘The Lower Triassic Xikou Formation in southwestern Fujian, China is a set of complex deep water sediments which includes turbidites, sandy contourites and isolated olistoliths. Five facies and seven subfacies are recognized in the deep water turbidites, which are considered to belong to five facies associations of upper, middle and lower fans, respectively. The sandy contourites, which occur within turbidites as isolated thin layers with structures of traction current, are formed by reworking turbidites. They occur in discrete units, not as a part of a vertical sequence of structures, such as Bouma sequence. Paleocurrent directions derived from sandy contourites are perpendicular to or at a large angle of those derived from turbidites. In some areas, within the Formation there exist large oolitic limestone blocks slided from shallow sea. The temporal spatial distribution of three types of sediments mentioned above and the related evidences could indicate that a passive continental margin from shallow sea to bathyal abyssal region, dipping toward southeast, once occurred in study area during the early Triassic. The early Triassic represents a period of sea level uprising. The uprising of sea level and the development of isolated olistoliths probably imply gradual shrinking of an ocean basin at that time.
