flua L. on steep escarpments in the Bosque Caducifolio. 
Pinus hartwegu Lindl. and P. rudis Engl. occur above 
2800 m. at the limits of tree growth, and on escarpments 
between 2800-8500 m. They may be accompanied by 
Abies guatemalensis Rehd. and Cupressus lindleyi Kluts. 
Pinus pseudostrobus, P. montezumae, P. hartwegu, P. 
teocote and P. oocarpa produce large quantities of resin, 
and hence are used for turpentine. The Pinares have a 
grass understory that is subject to periodic burning, and 
this provides a constant source of injury that increases 
resin production. 
Thus, if one assesses the possible habitats in which 
resin producers occur today in Chiapas, some seem more 
likely than others to provide opportunities for preserva- 
tion of resin. For this purpose, it is also important to 
consider the topographic and land-sea relations during 
the Oligo-Miocene to determine the environmental con- 
ditions in which the amber was being deposited. It ap- 
pears that the Chiapas amber was deposited near the 
southern edge of a broad seaway that covered much of 
southeastern Mexico and northern Guatemala. The en- 
vironment was primarily marine, but one in which oscilla- 
tions of the strand line produced occasional intertonguing 
of non-marine sediments. Geological evidence indicates 
that the ancestral Sierra Madre mountains were in exist- 
ence to the south at that time, although not as high as 
at present. It also appears that these mountains are the 
source of detrital materials in the amber-bearing 
sediments. 
It might be assumed that pines occurring in the Sierra 
Madre could have contributed the resin in Chiapas, just 
as it has been suggested that the resin was derived from 
pines in a mountainous area near the Baltic Sea. It ap- 
pears, however, that the proximity of the mountains was 
closer in the Baltic than in Chiapas, where they were 
[ 273 | 
