Magnetostratigraphy of marine sediment core MD01-2414 from Okhotsk Sea and its paleoenvironmental implications

This study used a paleomagnetic method to analyze the marine sediment core, called MD01-2414, taken from the Okhotsk Sea during the IMAGES VII cruise in 2001. The results indicate that the Brunhes/Matuyama boundary appeared at the depth of 27.76 m, with the age of 0.78 Ma. The lower and upper bounds of the Jaramillo event are located at 36.96 and 34.74 m depth, respectively. Cobb mountain event is found at a depth between 40.67 m and 41.06 m. Close to the bottom of the core, normal polarity is observed; it is proposed to be the termination of the Olduvai normal event. This event implies that this core signifies an age interval of about 1.8 Ma. Excursions could be identified from the paleomagnetic directional record, such as Kamikatsula, Santa Rosa; the relative paleo-intensity secular variation pattern also helped to delimit magnetic excursions in the Brunhes normal epoch, e.g. Iceland Basin event, Big Lost event, etc. Thus, the age model of this core can be well established. Based on the age model, the variations of magnetic susceptibility and ARM/χ of this core indicated that highly abundant but relatively coarse grain of magnetic minerals appeared in the even stages of oxygen isotope chronology, while low abundance with finer grain appeared in the interglacial periods. This suggests that there are different sources and transportation pathways of the sediments deposited in the area studied during glacial and interglacial periods. During the glacial time, terrigenous sediments containing abundant magnetic minerals eroded by the ice river from the Kamchatka peninsula were brought into the central Okhotsk Sea by the West Kamchatkan current (WKC), while the central and western parts of the Okhotsk Sea were completely covered by sea ice. During the interglacial time, the WKC and the East Sakhalin current (ESC) brought lots of terrigenous sediments from the north and west (the Siberia continent), which contain less abundant magnetic minerals and dilute the signal of magnetic susceptibility.