陸成層における堆積シーケンスの認定

研究の現状と今後の課題

抄録

Not a few papers concerning terrestrial sequence stratigraphy have been published during the last decade, as applications using sequence stratigraphic concept have increased. This paper reviews current developments in terrestrial sequence stratigraphy in terms of sedimentation control factors and recognition methods of depositional sequences in terrestrial strata. Terrestrial sedimentary environments are divided into three territories; coastal plains, transfer zones and inland basins. Relative sea-level changes are the most important control factors in coastal plains, whereas climate and tectonic movement are critical in inland basins. In coastal plains, a depositional sequence can be recognized by such strata indicative of marine incursion as tidal, bay, estuarine or shallow marine sediments, which constitute a maximum flooding surface. Frequency and size of fluvial channels are important signals for recognition of a depositional sequence in fluvial strata, because they may have been formed in response to changes of accommodation space corresponding to relative sea-level or base level changes. In inland basins, it is necessary to recognize cycles in relation with base level, climate and sediment supply changes. In any case, we need to improve terrestrial sequence models by carrying out further case studies on a large variety of geological settings.