Lucky lake a time-travel treasure trove

Lucky lake a time-travel treasure trove

An intriguing lake from the past has been discovered at a key study site, adding to the treasure trove of information already found there. This long-lost lake is expected to yield important clues as to how New Zealand landscapes have responded to climate change in the past.

The East Coast's Waipaoa hill catchments contain evidence of the effects of past storms via the sediment stored in their valley systems. Sediment records reveal relationships between erosion rates, vegetation cover and climate. They are crucial for understanding how land uses today might respond to climate change scenarios predicted for New Zealand.

While on a routine sediment coring expedition in Waipaoa, Landcare Research scientist Dr Mike Marden made a chance discovery of an infilled lake. The lake was formed some time in the past 10,000 years, and lasted long enough for an11-metre-thick pile of sediment to be preserved. It was probably formed when a major landslide blocked the river. The landslide-dammed lake is then thought to have drained when the river finally broke through.

"It's a lucky find * and an exciting one," Mike says. Our aim is to understand what's happening in the entire Waipaoa sedimentary system, from mountains to sea. Now for the first time, we can use this lake record to make direct correlations between what was happening in the landscape with records of sediment accumulation on the ocean floor in Poverty Bay at the time the lake formed. We can ask oceanographers if they can detect changes in sediment accumulation patterns in the Bay dating from the same time-frame

As well as alternating layers of sediment, the lake bed deposits contain volcanic ash and organic material including wood and pollen. The organic material can be carbon-dated, to give researchers an indication of when the lake was formed. Using the pollen to deduce what vegetation was growing will also provide an indication of what the climate was like at the time the lake sediments were deposited.

"This research will help establish relationships between climate, vegetation and landscape response at the time the lake existed," Mike says. "These relationships can then be used to predict what might happen given a similar combination of factors in the future."

ENDS

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