Tectonic controls on the stratigraphic development of the rifted Taipei Basin: A late quaternary marine-influenced inland half graben

We establish the three-dimensional stratigraphic architecture of the Taipei Basin and its spatiotemporal palaeoenvironmental development during the past 50 kyr by analysing 36 borehole cores and 177 age dates. We calculate the rates of basin subsidence from the borehole data at depths where radiocarbon age dates are available. Our results indicate that, during the eustatic sea level falling period (35-20 ka), low rates of sediment supply and/or rapid basin subsidence controlled sedimentation, leading to a change in the depositional environment from gravelly braided rivers, through sandy braided rivers, to meandering rivers with falling eustatic sea level. During the early stage of eustatic sea level rise (∼20-10.2 ka), balanced rates of sediment supply, eustasy and basin subsidence maintained the meandering river environment. Rapid sea level rise led to the initial appearance of estuarine facies at ∼10.2 ka and widened the distribution of the estuarine environment after 8.5 ka; however, the coeval phases of rapid basin subsidence ∼10.6-10.2 ka and 9-8.5 ka promoted the first appearance and widening of the estuary, respectively. After 7 ka, when the eustatic sea level and rate of basin subsidence remained relatively stable, sufficient sediment supply gradually infilled the estuary. The established stratigraphy improves our understanding of the factors controlling stratigraphic development in marine-influenced inland half grabens, specifically in the Taipei Basin with high rates of sediment supply. Accommodation space in the Taipei Basin was governed by eustatic fluctuations with modulations by basin subsidence and sediment supply since the last glacial period.