黔南中三叠统江洞沟组浊积岩特征

贵州中三叠世拉丁尼克期古地理分异明显其西北侧属浅海台地,东南侧为开阔海盆(图1)。盆地相沉积称江洞沟组,是一套砂泥岩组合类复理石沉积,厚逾数千米,在贞丰联合厚达3000余米,尚未见顶。

TURBIDITES FORM THE MIDDLE TRIASSIC JIANGDONGGOU FORMATION IN SANCHAHE AREA,SOUTHERN GUIZHOU

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