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RE: mass extinctions and technology



Jeff,

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 3-25 ppb.

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.

Cheers,
Mark

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 been examined.

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