Learn all about CLAMP over at
http://tabitha.open.ac.uk/spicer/CLAMP/Clampset1.html , a web site put
together by Jack Wolfe and Bob Spicer. CLAMP is a scientific technique
used to approximate the paleoclimate of a specific fossil plant
locality through a sophisticated analysis of leaf physiognomy (size,
shape, venation, for example). Here's a quote from the "Background"
section of the web page:

"What is CLAMP?

Climate Leaf Analysis Multivariate Programe (CLAMP) (Wolfe, 1990,
1993; Kovack and Spicer, 1995; Wolfe and Spicer, 1999; Spicer, 1999)
is a multivariate statistical technique that decodes the climatic
signal inherent in the physiognomy of leaves of woody dicotyledonous
plants. It was developed as an evolutionarily robust, accurate, and
precise tool for direct atmospheric palaeoclimate determinations over
land, and as such complements marine-based climate proxies such as
oxygen isotopes. CLAMP calibrates the numerical relations between leaf
physiognomy of the woody dicotyledons and meteorological parameters in
modern terrestrial environments. Using this calibration, past climatic
data are potentially determinable from leaf fossil assemblages
provided that the calibration is robust over time and that the
sampling of the fossil assemblage represents well the characteristics
of the living source vegetation. CLAMP has been applied effectively to
fossil floras up to 100 million years old (Herman and Spicer, 1996),
but is an even more powerful and reliable tool for late Tertiary
(Wolfe, 1995; Spicer, 1999) and Quaternary assemblages."

Paleobotanical Field Trip To The Sailor Flat Hydraulic Gold Mine,
California
http://esmeralda.topcities.com/sf/sailorflat.html