Origin of annual laminations in tufa deposits, southwest Japan

Akihiro Kano, Jun Matsuoka, Tomoko Kojo, Hidenori Fujii

Research output: Contribution to journalArticlepeer-review

119 Citations (Scopus)


Laminated tufas and a tufa-depositing stream in SW Japan (Shirokawa, Ehime Prefecture) were studied monthly over a 3-yr period. A series of samples from the tufa clearly reveals the pattern of annual laminations. The annual layering pattern was primarily controlled by changes in the rate of calcite precipitation, as calculated from water chemistry. The concentration of dissolved CaCO3, which correlates with the precipitation rate, was high in summer-autumn and low in winter-spring, owing to changes in the partial pressure of CO2 in underground air. Regular seasonal changes in underground PCO2 probably resulted from two temperature-dependent processes, the diffusion of soil CO2 and the ventilation of underground air. These changes, in addition to water temperature changes, altered the precipitation rate, which has a clear seasonal pattern, especially in the lower stream. The seasonal precipitation rate was high in summer-autumn and low in winter-spring, which is consistent with the seasonal lamination pattern seen in the tufas. The textures of collected samples show that the laminations consist of densely calcified summer-autumn (June-October) laminae and lightly calcified winter-spring (November-May) laminae. We infer that the increased precipitation rate stimulated thick calcite encrustation on cyanobacterial filaments to produce the dense textures. This interpretation is supported by the lowered organic/inorganic carbon-production ratio in summer-autumn. Seasonal variations in cyanobacterial assemblages are present, but do not reflect the seasonal lamination pattern. Because the relevant processes are temperature dependent, the seasonal lamination pattern at Shirokawa is thought to generally apply to other laminated tufas deposited in temperate climates. However, a reversed pattern can result from local and climatic circumstances. Dense laminae were deposited in winter near the source of the spring at Shirokawa, because calcite precipitation was high owing to low underground PCO2 in winter. Reversed patterns reported from northwestern Europe were probably influenced by seasonal rainfall, which is reflected in hydrological conditions.

Original languageEnglish
Pages (from-to)243-262
Number of pages20
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Issue number2
Publication statusPublished - Feb 15 2003
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Earth-Surface Processes
  • Palaeontology


Dive into the research topics of 'Origin of annual laminations in tufa deposits, southwest Japan'. Together they form a unique fingerprint.

Cite this