Takeshi Nakagawa, a professor at the University of Newcastle, was first involved in sediment sampling at this lake in 1993, he told reporters in a news conference. The first scientific paper from that core sample published in 1998. But the 1993 core was not a continuous sample, with gaps between different layers--so just like other calibration techniques, it was unclear exactly how the years matched up, making it an incomplete record. After obtaining funding from the UK's Natural Environmental Research Council, Nakagawa took another core in 2006. It's fully continuous, with overlapping layers, dating to 52,800 years ago.