Sedimentary Facies of the Gaoping Submarine Canyon
TSUNG-YI LIN (886-2-83693413; aeolin@ntnu.edu.tw)
Department of Geography, National Taiwan Normal University, 162, Ho-ping E. Rd.,, Sec. 1, Taipei
10610, TAIWAN
Abstract
Three cores, each approximately 3.5 to 4.6 meters long, taken along the Gaoping Submarine Canyon
were examined by variations in grain size, sedimentary structures and the organic contents to recognize
their sedimentary facies and to interpret their possible processes of deposition. Three cores of the
Gaoping Submarine Canyon were taken from the head, the mid-section, and the end of the canyon
respectively. Each core was sliced longitudinally to two halves and was x-ray radiographed,
photographed, and visually described. Three main units of sedimentary sequences are recognized in
these cores: (1) a fining-upward unit with sharp erosional base contact that varied from coarse silt or, in
some cases, very fine sand to clay, (2) a fine parallel-laminated silt/clay alternation layer, and (3) a grey
muddy deposit with scattered, brown organic matters. The core taken from the head of canyon is
mainly characterized by the fining-upward units and the silt/clay alternation layers in between. The
cores taken from the mid-section and the end of the canyon have similar characteristics in that they
consist of mainly the silt/clay alternation layers. These layers appear as black silt laminae alternate with
grey clay laminae. The silt-grade sediments consist mainly of the black slate fragments. The
fining-upward units in the core from the head of canyon may be produced by hyperpycnal turbidity
currents triggered during typhoon-related flash floods. The alternation of silt and clay laminae may be
explained by the alternation of burst events in the basal boundary layer, as well as normal hemipelagic
background sedimentation. One extra core taken from the nearby ocean basin that has a similar water
depth with the one taken from the end of the canyon is characterized by the grey clay deposit in the
entire core, which may be a distinctive sequence representing the hemipelagic mud deposition.
Key words: sedimentary facies, Gaoping Submarine Canyon, hyperpycnal turbidity currents, hemipelagic mud