Abstract:

Datong Volcano eruption is an important geologic phenomenon of the Quaternary in North China and has been attracting scientists' attention; however, its episodic activity has remained unclear. Here, we demonstrate some new findings to reveal the episodic activity of the volcano during the Quaternary. (1) Volcano clastic layers with different ages which deposited near the paleolakeside incline with dip angles of 30°, 21°, 9° and 4°, respectively. (2) There exist four fine volcano clastic layers in the grayish-green lacustrine sediment in the paleolake inshore. (3) There are four sediment layers in the center of the paleolake which display high magnetic susceptibility value, indicating that some volcanic ash may deposit in them. Besides, the grain size of the four lacustrine layers is much coarser than that of others. (4) There exist three sediment layers in the loess section in the land some away from the paleolake, which display high magnetic susceptibilily value and low Rb/Sr one, indicating that some volcanic ash may deposit in them. (5) Magnetic boundary of B/M and Jaramillo Positive Subzone were found in the lacustrine section in the center of the paleolake. Based on these findings, we deduced that (1) Datong volcano experienced four episodic activities during the Quaternary and there occur many times volcano eruptions during each episodic activity; (2) the beginning times of four episodic activities are older than 0.90 Ma BP, ~0.47 Ma BP, ~0.31 Ma BP and 0.09 Ma BP, respectively; (3) another episodic activity with the beginning time ~0.19 Ma BP was also recorded in regional loess sediment; (4) the occurrence of each of the episodic activities of the volcano is synchronous with that of each of the paleolake regressions, implying that there is some relationship between the volcano eruptions and the paleolake regressions.

Key words: Datong volcano, lacustrine sediment, loess sediment, dating by paleomagnetism