The Early Cretaceous lagerstätten of NE China

Barely a month passes without some weird fossil emerging from the widespread excavations in Early Cretaceous lacustrine sediments of north-east China.  It is probably the most productive palaeontological formation in the world, and has shed light on more than just the dinosaurian origin of birds, and rives ideas on the rise of angiosperm plants and early mammals.  As well as abundant fossils, the lagerstätten formed under low-oxygen conditions and preserves exquisite detail of soft tissue.  A review of the material and the environment in which it formed is welcomed by all palaeontologists (Zhou, Z, Barrett, P.M. & Hilton, J. 2003.  An exceptionally preserved Lower Cretaceous ecosystem.  Nature, v. 421, p. 807-814).  Zhou et al. Discuss the formation from two angles.  Scientifically their focus is on the potential for building a complete ecosystem for the area during the Early Cretaceous.  However, they also record the massive problems that result from haphazard collection by organised teams of locals and fossil dealers – incidentally the source of the infamous Archaeoraptor forgery (see “Piltdown” bird, in March 2001 issue of Earth Pages News).  Their review is also a plea for some kind of firm regulation of collection, although experience from many other lagerstätten suggests that is unlikely in the short-term.

Did terrestrial life emerge later than geochemists think?

A lot hangs on the notion that life can make it from abiogenic chemistry very quickly once a world has watery seas.  Evidence from oxygen isotopes in the oldest known terrestrial zircons suggests that liquid water was around on Earth by about 4400 Ma (see Pushing back the “vestige of a beginning” in Earth Pages News of February 2001, and The Hadean was cool June 2002).  It lies behind the search for signs of life on Mars and the fiasco surrounding the premature announcement of bacterial fossils in a meteorite reputedly from the Red Planet.  Right here, controversy has been raging over the once-living status of tiny patterns in 3500 Ma cherts from Western Australia (see Doubt cast on earliest bacterial fossils in Earth Pages News, April 2002), and on the true significance of isotopically light carbon trapped in apatite crystals in the 3800 ma Akilia metasediments of West Greenland.  Both have been claimed as signs of early, well-organised life, but the evidence is circumstantial.

Investigative journalism is very welcome in science, mainly because most scientists are either too polite, or grumble quietly in the coffee room.  Jon Copley, who teaches at Southampton University, has ventured into the field by interviewing some of the main antagonists in the “Is this a sign of life” debate (Copley, J. 2003.  Proof of life.  New Scientist, 22 February 2003, p. 28-31).  His article is most revealing, by getting down to brass tacks.  There is a lazy tendency in science to invoke William of Ockham’s “Razor”, i.e. that the simplest explanation of data is the best.  That is fine for the Old Bailey, in the manner of Roman legal argument of cui bono (who benefits?), but the natural world has a cussed tendency to pay no attention to human linear thought,  It is not a place for “elegance”, no matter how much scientists feel in awe of elegant mathematical proofs.  That it is wielded in favour of the most complex process in the universe to account for geochemical and other data is a bit odd.  Central to Copley’s sharp journalism lies something of which C-isotope specialists do not speak much.  At temperatures around 400ºC and a few hundred times atmospheric pressure can result in carbon monoxide and hydrogen combining to form hydrocarbons.  Fischer-Tropsch synthesis of hydrocarbons that fuelled Nazi Germany and South Africa under apartheid does occur in nature.  The ideal place is around deep-sea hydrothermal vents.  The reactions favour 12C over the heavier 13C and results in d13C just as negative as do living processes.  Isotopically light carbon in rocks that do not contain cast iron confirmation through tiny fossils, cannot be seen as proof that life existed.  Probably the oldest irrefutable fossils are of bacteria in the 1900 Ma Gunflint Chert of Ontario.  If we cannot be sure that C-isotopes help detect living processes on the early Earth, then results from missions, such as Beagle-2, to Mars could be exercises in futility.

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