台灣西南部化石珊瑚礁的發育和衰退過程及其古海洋環境的研究(2/2)
Date Issued
2003
Date
2003
Author(s)
DOI
912611M002022
Abstract
Pleistocene scleractinian reefs in SW Taiwan developed on several local structural highs that
were closely associated with anticlines and faults in a Plio-Pleistocene foreland basin.
Lithological successions of these fossil reefs are characterized by rapid facies changes from
the underlying mudstone foundations upward into fossiliferous mudstones, then into reef
limestone lithofacies. This study investigated how these coral reefs were able to establish
in an environment dominated by fine-grained siliciclastics. Detailed studies of 3 quarry
outcrops and 44 borehole cores reveal 5 types of local pioneering sedimentation at or near
the base of the carbonates: (1) mound-like dolomitic mudstones, (2) dolomitic lithoclasts, (3)
dolomitic conglomerates, (4) chimney-like dolomitic tubes, and (5) plume-like dolomitic
mudstones. Abundant in situ lucinid bivalves were found from one of the mound-like
dolomitic mudstones, with the tops encrusted with coralline algae, then overlaid by
bioclastic limestone. In addition, four types of facies changes from underlying mudstone
upward into the bottom of the reefal limestone were recognized. These successions suggest
that the mudstone substrates at many locations were firm ground or hardground before the
development of coral reefs, and served as the substrate on which sessile organisms were able
to colonize in a muddy environment. According to the co-occurrences of dolomitic
mudstones and fossil lucinids, as well as the tectonic setting of the study area, it is suggested
that cold seep carbonates developed during shallowing of the structural highs in SW Taiwan,
and served as the hardground and carbonate factories for the initial development of coral
reefs in the siliciclastic environment. The occurrences of dolomitic lithoclasts, muddy
conglomerate, and scouring of the upper most mudstones mark an erosional event occurred
on these structural highs. It suggests that these lithologies were formed and deposited as
the result of gas hydrate degassing, which was possibly triggered by the impulsion of
tectonic activities such as earthquakes.
Subjects
Cold seep carbonates
coral reef
foreland basin
lucinids
dolomites
Publisher
臺北市：國立臺灣大學海洋研究所
Type
report
File(s)![Thumbnail Image]()
Loading...
Name
912611M002022.pdf
Size
274.82 KB
Format
Adobe PDF
Checksum
(MD5):cf75ac009d756f1efbd24b838a017567