Geoscience Reference
In-Depth Information
throughout the Cenozoic. Macroscopic plant remains preserved in packrat middens
have provided a uniquely detailed picture of late Quaternary vegetation changes in
the deserts of northern Mexico and the south-west United States. Out of this work has
come the realisation that the responses of the biota to climatic change can be quite
variable, with some species showing a synchronous response, others a delayed but sud-
den (or step-function) response and others showing a delayed and time-transgressive
(or diachronous) response. Paradoxically, the fossils that provide the best overall
chronologic control of global climatic changes are not found in the deserts but in the
oceans, where the marine foraminifera have provided a detailed record of Cenozoic
changes in global temperature and of the Quaternary glacial-interglacial cycles which
had such a profound effect on desert environments.
