Geoscience Reference
In-Depth Information
WET
DRY
Classic Maya
Collapse
0
Carbonate
Gypsum
1000
2000
Carbonate
3000
4000
Laminated
mud
5000
6000
Carbonate
Gypsum
7000
0
5
10 15
12 3
S (
)
0/00
18
O (per mil)
Figure 2.10. 18 O measurements and stratigraphy from lake sediments on Yucatan
Peninsula, Mexico showing a severe drought that corresponded to the 'Classic Maya
Collapse' between AD 800 and 900 (note that the figure shows radiocarbon years not
calendar years; after Hodell et al ., 1995).
Although a post-classic resurgence occurred in the northern Yucatan, city-states
in the southern lowlands remained sparsely occupied. The
18 Orecord suggests
that drought played a significant role in causing major cultural discontinuities
in Classic Maya civilisation.
Nitrogen isotopes
Based on analogues created from modern studies of fauna, nitrogen iso-
tope analysis can be used to determine dietary and trophic relationships in fossil
animals. Factors that determine the content of
15 Nincollagen from herbivores
include the level of soil nitrogen cycling which affects the isotopic composition
of plants and the nitrogen metabolism of the animal itself. This variability in
15 Nisdependent on both the animal and the surrounding environment. Fac-
tors affecting the overall level of
15 Ninherbivorous animals include salinity,
open environments, urea concentration, monogastric digestive systems, age and
suckling (Grocke et al ., 1997). Higher values of
15 Nare thought to represent
progressively more arid conditions.
In
15 Nvalues of
macropods to estimate palaeoprecipitation levels. Analyses were conducted on
species where both modern environmental and physiological characteristics
were known. The results showed that changes in
Australia,
attempts
have
been
made
to
use
collagen
15 Nvalues correlate well with
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