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RE: mass extinctions and technology
The inorganic geochemistry may indeed have something interesting to
say. Professor Robert Brooks (Massey University, New Zealand) wrote to me:
"There is indeed a small Hg anomaly at the K/T boundary, as there is for
many other chalcophile elements. For example Varekamp and Thomas in Geol
Soc Am Prof Pap. 190 (1982) 461-467, reported 75-1000 ppb Hg in K/T
sediments from Denmark and Spain. The corresponding signatures for Ir were
The reason I am interested in specific organic geochemical tracers (PCB's,
DDT, phthalates), is that they are of exclusively industrial
origin. ie. a kitchen sink, found in the right environment might
unambiguously indicate a PHC, but it would be very difficult to implicate
trace metals as evidence of a PHC, simply because you can invoke "natural"
mechanisms for trace metal anomalies. In contrast, PCB's are the
microscopic equivalents of a kitchen sink. They rank amongst human beings
smallest mass produced artifacts. They don't occur in "nature" at
all. Neither does DDE (the stable metabolite of DDT).
I put "nature" in quotes because I believe humans (and therefore all our
constructs) are ultimately products of nature. That we humans distance
ourselves so greatly from nature, and invent words like "anthropogenic",
"synthetic" or "natural", might explain out reticence to accept that nature
could produce 20th century technology on a routine basis.
50% of the worlds flora and fauna could be on the path to extinction within
the next 100 years - National Geographic
At 08:41 AM 30/09/2002 -0400, you wrote:
At 12:56 PM +1000 9/30/02, Mark Harvey wrote:
You have got to start somewhere. To my knowledge, the organic
environmental geochemistry of extinction boundary sediments has never
The inorganic geochemistry also may have something interesting to say. For
example, lead levels in sediments have been elevated since lead mining
started in Roman times. I believe they dropped in medieval times, then
rose in the industrial age.
-- Jeff Hecht