So what is now a geopark would have been a tropical climate, host to an abundance of life. Once cut off from the open ocean, the isolated sea would become overcrowded. Deep sea creatures, such as ichthyosaurs, would die of suffocation under these conditions. For the same reason – lack of oxygen – the decomposition of corpses on the seabed would have been very slow. New sediments covering the corpses before their bones were decomposed would have further insulated them from any oxygen, so all remains were well preserved and later fossilized. This of course was a long process and may explain why fossils of different species from different periods jammed together at Guanling.

    All of which gave rise to a new question. In Guanling, the thickness of the Triassic strata is more than 1,000 meters, and the thickness of the fossil deposit is less than 10 meters. This means in the longer geological eras, the Guanling-type marine life spanned only one million years, a walk-on part in geological time. Was their demise a much more sudden occurence than the previous explanation suggests?

    An unexpected answer to this question arrived one day, through a field team's serendipitous selection of a campsite.

    The geological group of Guizhou Provincial Bureau of Geology and Mineral Exploration chose to set up camp in the river valley. At daybreak, strangely-shaped rocks on a section of the cliff came to their attention. Two rocks of the same stratum were rolled up like pancakes. They are what geologists call the slump structure, convoluted bedding caused by strong quakes under the sea and the recession of water. They believe that a sudden destructive occurrence doomed all Guanling marine life.

    Professor Jiang Dayong disagrees with this hypothesis. "It takes a long time for a fossil stratum to form. In my opinion, a series of incidents caused the living things to die of suffocation due to oxygen deficiency over a period of one million years. At present, we have found signs of volcanic ash, but have not found more evidence of volcanic eruption."

    What has been found are traces of earthquake activity hundreds of million years ago in Guanling, by Chen Xiaohong, a research fellow with the Yichang Geology and Mineral Institute of Hubei Province.

    "After all, our research on the Guanling fossils has been underway less than a decade, and many hypotheses need to be proven or otherwise," said Jiang Dayong.