Sequence stratigraphy of the Silurian strata and accommodation spaces in central Tarim Basin,Xinjiang

The Silurian strata in central Tarim Basin,Xinjiang may be grouped,on the basis of classical sequence stratigraphic theory,and outcrops,well logs and seismic sections,into five sequences,of which four are assigned to the type 2 sequence except SQ1 as the type 1 sequence.Each of them consists of transgressive and highstand systems tracts.SQ3 is interpreted as a third-order intermediate system tract.Influenced by the Caledonian orogeny,the uplifted central Tarim Basin area was subjected to the erosion during the Late Ordovician,followed by the deposition of the tidal flat-dominated Silurian littoral and shallow marine deposits.The Silurian time was tectonically quiet in this area.The eustatic fluctuations may exercise a major control on the sizes of the accommodation spaces.The migration of the tidal-flat facies has mirrored the variations in accommodation space and tidal energy,and represents the products originated from the combination of autocyclic and allocyclic deposition in response to the global eustatic fluctuations.The dynamic patterns of the accommodation spaces may be the external expressions of tidal cyclicity.