Research press release


Nature Communications

Evolution: Iron-ing out the creases in global kill mechanisms



今回、Matthew Clarksonたちは、高精度の化学的手法(鉄スペシエーション法)を用いて、数百万年前の新テチス海(現在のオマーン)の堆積物である岩石に保存された古代の海洋の化学組成を解析した。古代の浅瀬から深海までの6か所の試料採取場所の化学データから明らかになったのは、これまで予測されていたように有毒な硫黄を多く含む状態が広範に存在するのではなく、鉄を豊富に含むが酸素の少ない海洋の中に酸素を豊富に含むポケットが点在する状態だった。


Iron-rich, oxygen-starved oceans delayed the recovery of life following the Earth’s greatest mass extinction 252 million years ago, according to a study published in Nature Communications this week. The findings shed light on the ancient ocean chemistry responsible for the longest recovery period following a mass extinction in Earth's history.

Toxic, sulfur-rich oceans have long been considered the global kill mechanism responsible for the loss of 90% of the planet’s biodiversity at the end of the Permian period (252 million years ago), and the protracted 5 million-year recovery that followed. However, the global nature of this extreme oceanic state is based on limited geochemical tools and is rather poorly constrained.

Matthew Clarkson and colleagues use highly precise chemical techniques (known as iron-speciation techniques) to analyse ancient ocean chemistry preserved in rocks laid down as sediments in the Neo-Tethyan Ocean (modern day Oman) millions of years ago. Chemical data from six sampling sites, spanning the ancient shallows to the deeper ocean, reveal iron-rich, oxygen-poor conditions, punctuated by oxygen-rich pockets, rather than the widespread toxic sulphur-rich conditions previously predicted.

Although the precise cause of this extended recovery period remains unclear, the authors believe enhanced chemical weathering on land (due to high temperatures) led to increases in the flux of iron to the oceans, which would have sustained the iron-rich, low-oxygen state, and suppressed biotic recovery.

doi: 10.1038/ncomms12236

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