From: Andy Soos, ENN Published March 18, 2013 04:44 PM  The
First Oxygen Poor World Ocean  A research team led by
biogeochemists at the University of California, Riverside has
filled in a billion-year gap in our understanding of conditions
in the early ocean during a critical time in the history of life
on Earth. Over time, the planet cooled and formed a solid crust,
allowing liquid water to exist on the surface. The first life
forms appeared between 3.8 and 3.5 billion years ago.
Photosynthetic life appeared around 2 billion years ago,
enriching the atmosphere with oxygen. Life remained mostly small
and microscopic until about 580 million years ago, when complex
multicellular life arose. It is now well accepted that
appreciable oxygen first accumulated in the atmosphere about 2.4
to 2.3 billion years ago. It is equally well accepted that the
build-up of oxygen in the ocean may have lagged the atmospheric
increase by well over a billion years, but the details of those
conditions have long been elusive because