Detrital zircon U-Pb ages of Late Cenozoic sediments from the Yangtze delta:Implication for the evolution of the Yangtze River

Detrital zircon grains of Late Cenozoic sediments dated back to ca.3.6 Ma from core DY03 in the Yangtze delta were dated by LA-ICP-MS,in order to investigate the sedimentary provenance and to find some clue for the evolution of the Yangtze River.Most of the detrital zircon U-Pb ages are distributed at 100 300 Ma,350 550 Ma,600 1000 Ma,1400 2000 Ma and 2200 2800 Ma,which correspond well with the main tectonic and magmatic events in the Yangtze drainage.The detrital zircon age patterns show distinct difference between the 3 samples below 189.8 m and other 6 above 189.8 m.43% 55% zircons in the 3 samples below 189.8 m fall within Cretaceous,while ages from 150 to 2800 Ma are distributed with no obvious peaks,which indicate the sedimentary provenance may be limited to the lower Yangtze drainage.The 6 samples above 189.8 m show similar age patterns,and the ages are relatively evenly distributed,indicating the sedimentary provenance broadened distinctly.All 6 samples deposited later than ca.3.2 Ma show age information from the upper Yangtze drainage (including the Emeishan large igneous province),indicating that the Three Gorges may have already been cut through by then.