THE CHARACTER OF STREAMS FROM THE CENTRAL RANGE, TAIWAN: AN ANALOGY TO THE HYDROLOGY OF NEW ENGLAND AFTER THE TACONIC OROGENY

The physical and chemical weathering of high-standing islands and other island arc regions have been recognized to be a major contributor of sediments to today's oceans as well as to be a major locus of CO2 consumption via aluminosilicate weathering. Our work in the Central Range, Taiwan where uplift rates are 0.5cm yr-1 suggest, although physical erosion yields are extremely high, absolute rates of chemical weathering are also very high with dissolved Si yields of ~7800 mol ha-1 yr-1. The paleolatitude of portions of the Ordovician age Taconic Highlands (TH) of the northeastern U.S. is similar to that of Taiwan today. By analogy, the chemical and physical weathering yields documented in Taiwan by us and others may have been very similar to those that existed in New England during the mid to late Ordovician, when more than 600,000 km3 of sediment was introduced into the Queenston Delta alone from the TH. At current Taiwan denudation rates the accumulation of this amount of sediments would take less than 10⁷ yr. High aluminosilicate weathering rates of the TH would have produced increased fluxes of nutrients, especially phosphorus, which would have led to increased marine primary production and enhanced organic carbon burial. Both increased organic carbon burial and chemical weathering would have led to extensive drawdown of atmospheric CO2. The importance of island arc weathering in the carbon cycle has been under appreciated until recently. Our recent work suggests that these regions have also been important links to carbon dynamics in the geologic past.