Patterns and sizes of authigenic carbonate formation in the Pliocene foreland in southwestern Taiwan: Implications of an ancient methane seep

Chih Wei Chien, Chi Yue Huang, Hong Chun Lee, Kenn Ming Yang

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Several dolomitic authigenic carbonate concretions (ACCs) are preserved in the Pliocene foreland sequence in southwestern Taiwan. Carbon isotopic signatures and the morphology of these carbonates and associated chemosymbiotic bivalve fossils reveal their methane seep origin. There are three types of ACCs: (1) massive brecciated blocks (MBBs; δ13C = -49.57 ∼ -38.20‰; δ18O = 1.59 ∼ 4.25‰); (2) giant chimneys (GCs; δ13C = -43.14 ∼ -17.73‰; δ18O = -7.64 ∼ 3.36‰); and (3) slender pipe networks (SPNs; δ13C = -43.51 ∼ 5.91‰; δ18O = -6.90 ∼ -3.57‰). Different shapes, sizes, stratigraphic positions, and carbon isotopic compositions are due to different flux/intensities and flow pattern of discharging methane. MBBs were derived from diffusion of methane and formed in deeper positions, whereas GCs mark the locations of feeder faults and main outlets of methane emission. SPNs formed along fractures or bedding planes; they were (1) accessories of MBBs and GCs, or (2) products of minor releases of residual geofluids. We compared ACCs of the Chiahsien Paleoseep to two previously studied cold seep carbonates within the same foredeep in southwestern Taiwan, which represent similar occurrences and stable carbon isotopic compositions. However, the older ACCs in the Chiahsien Paleoseep have undergone longer diagenesis and weathering processes and have more complicated and lower δ18O signatures. These asynchronous cold seep carbonates can indicate hydrocarbon migrations and fault activities within the orogenic belt of Taiwan.

Original languageEnglish
Pages (from-to)971-984
Number of pages14
JournalTerrestrial, Atmospheric and Oceanic Sciences
Volume24
Issue number6
DOIs
Publication statusPublished - 2013 Dec

All Science Journal Classification (ASJC) codes

  • Oceanography
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)

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