Terrigenous flux and biogenic silica deposition at the Antarctic continental rise during the late Miocene to early Pliocene: implications for ice sheet stability and sea ice coverage

Drift sediments recovered from the East Antarctic continental rise at Ocean Drilling Program (ODP) Site 1165 are used to infer variations in East Antarctic Ice Sheet (EAIS) stability and sea ice coverage during the late Miocene and early Pliocene. A significant increase in the deposition of biogenic opal from ∼5.8 to 5.2 Ma points to an early Pliocene reduction in sea ice and a subsequent increase in biological productivity. Time intervals at ∼7.2 to 6.6 Ma and ∼5.2 to 4.8 Ma are characterized by pronounced maxima in the long-term trend of terrigenous matter accumulation (MARter) indicating high continental erosion rates potentially caused by ice sheet growth. A Southern Ocean wide impact of these events is suggested by similar evidence found at ODP Site 1095 (Antarctic Peninsula). Superimposed on the MARter maxima we observe enhanced orbital variability in iron accumulation at Site 1165 pointing to a dynamic behavior of the EAIS with waxing and waning ice masses. From the concurrence of these high amplitude ice sheet fluctuations with maximum variance in Earth's obliquity, we propose that the insolation gradient between high and low latitudes affected the delivery of moisture to Antarctica and thus controlled ice volume variations.