Sanchahe area

Luodian County

Guizhou Province

was in the northern margin of Guizhou-Guangxi Sea Basin and to the south of the Bangen atoll during Ladinic stage.A series of beautiful turbidites with distinct rhythm was deposited there

containing small amount of ammonites

Pelecypoda and other organic clastics.These sediments are now described as the Jiangdonggou Forma-tion

which have following characteristics:1.The rhythmic bedding is quite distinct and the Bouma cycle can be clearly distinguished with B

C

D

and E intervals being hingly developed.Among other things

the D-E and B-E sequences are more common.2.Various kinds of underside casts

such as flute casts

groove casts and load casts were developed there.The paleocurrent direction can be determined by the flute or groove casts ranging 268-297°.3.Major component of these sediments is feldspar

and then quartz.The argillaceous material occupies 3-35%

while the calcite matrix (cement) is 1.5-30%.Therefore

the sediments belong in feldsparthic sandstone.The round-ness of particles is poor and grain size are usually more than 4φ.4.As for parameters of grain-size

the average diameter (Mz) of particles isof 4.073φ

belonging to silt size;the standard deviation (σ

1

) is of 0.738

indica-ting middle degree of sorting;the mean skewness (SK

I

) is of-0.0002

expressing approximate symmetry;the average value of kurtosis (Kg) is 0.9369

showing approximately normal distribution;the average discriminant score (Y) of envi-ronment (river or turbidity flow) is of 7.6725

representing turbidity current.5.In aspect of graphic feature

straight line and simple brokenline are reproduced on probability diagram of grain size with low slope ranging from 32° to 64°

suggesting mainly a graded suspension transport

but a small amount of saltation transport may have taken place.CM diagram shows parallel C=M spacing.According to sedimentary sequence

underside casts

grain-size and graphic feature

it is Presumed that the Jiangdonggou Formation was the distal facies of turbidity current far from its provenance.