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SEDIMENTOLOGICAL STUDY OF A SECTION OF THE "UPPER ZIGZAG" FORMATION ALONG BUED RIVER, TUBA, BENGUET

ROLAND0 E. PENA AND MILAGROS V. REYES

 

 

 

 

ABSTRACT

 

Sedimentological study of the sedimentary section below the Middle Miocene Kennon Limestone along Bued River consisted of detailed description of selected local sections and subsequent evaluation of primary sedimentary structures and detailed petrographic analysis of representative rock samples.

Primary sedimentary structures shown mostly by sandstone interbeds in the dominantly conglomerate section are parallel lamination and cross stratification, normal and reverse graded bedding. Slump structures and sandwaves were also noted. Paleocurrent directions derived from reoriented foresets of cross-stratification indicate a southwestern, source of the sediments.

Textures and composition of the wackes and conglomerates of the section studied suggest that the sediments were principally derived from a volcanic terrain with considerable relief. These sediments were probably deposited in a nearby shallow marine basin by very strong fluvial currents whose energy diminished as it reached the basin area. Intermittent changes in current velocity during transport and at site of deposition were most likely responsible for the development of small and large scale cross stratification.

 

 

 

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