Muti-proxies records at mid-Pliocene (MIS M2) of benthic foraminifera <i>Melonis</i> spp.

The M2 glaciation is a prominent event in the benthic oxygen isotope stack around 3.3 million years ago, and has often been thought of as an early but failed initiation of Northern Hemisphere glaciation. However, recent work has cast doubt on this assumption, and suggested that the δ¹⁸O signal reflects predominantly cooling of deep waters, not growth of continental ice. The <i>Melonis </i>spp. δ¹⁸O and Mg/Ca approach was improved by looking into the effects of test size of <i>Melonis</i> on both stable isotope (δ¹⁸O, δ¹³C) and trace metal composations. Applied the improved approach at Atlantic ODP Site 982 and Pacific ODP Site 1241, a dynamic cryosphere during M2 glaciation, and its intriguing relationship with ocean temperature, circulation changes, and pCO₂ was revealed.