Paleomagnetic Investigation Of Salawusu Stratum

Scholars have studied the salawusu stratum which is regarded as Late-Pleistocene river-lake standard stratum in north of china by traditional Geological method, and have acquired some basic opinions. But there are some defferent opinions in age range , sediment environment , sediment mechanism, At the same time, studying degree is not enough either. It is important to study salawusu stratum using paleomagnetism method , to give some magnetic proof in age range, stratum correlation,paleoenvironment and paleoclimate, to test former research result.This paper has done systemic paleomagnetism investigation, at Dishaogouwan section Its magnetic character is : susceptibility value is relatively high and its curve fluctuates little, magnetic mineral is mainly magnetites. The susceptibility AMS ellipse is oblate. Anisotropy is not obvious in sterenet projection. NaturalRemanent Magnetization is congregate, locates the northern hemisphere, and is basically consistent with present geomagnetic field . The average Dec i 9.4,Inc is 42, Q value's low-high-low change i correspond with oxygen isotopy curve's cold-warm-isiscold change . 13 is positive and its average value is 82?. Most of minimum AMS components are projected on the circle's center. Maximun AMS components distribute everywhere. After AFdemagnetizing, most of samples show one paleomagnetic component; analyzing these magnetic characters using paleomagnetism theory , The conclusion is: salawusu sediments were formed in warm-humidity environment, its sediment environment is relatively stable. The directional distribution of NRM is basically the same as the present geomagnetic field. The timecorresponding to the four parts along the section are as follows: The top lake-swamp sediments: Holocene;the uppart fine sand: Later Late Pleistocene; The middlepart sandy clay: Middle-Early Late Pleistocene; The lowpart clayer silt:Later-Middle-Pleistocene. the fossils and stone artifacts found in salawusu site should be formed during the last but one glacier, its age range is about 0.13-0.19 Ma, and belongs to later Middle-Pleistocene.