Summary. Biogeochemistry provides precious information about system dynamics of multidimensional system (i.e. what the main forces and elements are acting within the system, and how these forces and elements have changed in space and time). System dynamics patterns are applicable to many different fields including amongst others the biosphere, environmental sciences, anthropology and. In all of these fields biogeochemistry has proved to be very useful.

Geochemical analyses performed on the ostracod valves of a core, give information about the fluctuations, during a time span, of temperature, salinity, rainfalls and primary productivity of the setting they inhabited. Examples of the applications of ostracod geochemistry from palaeoclimatology to archaeology are described:

-Geochemical analyses performed on the ostracod valves from a core log sampled in Titicaca lake, on the Bolivian Altiplano, have given results which are congruent with the micropalaeontological analyses, but differ with the results regarding the water level of the lake, based on sedimentological analyses. A revision of the curve of the level of the lake and a palaeoclimatic interpretation of this curve are discussed.

-In the Camargue, delta of the Rhone, France, an ongoing project focalises the hydrological risk during the Middle Ages on the delta, its origin, characteristics, frequency, effects, consequences and political reactions from the local management during that period. Geochemical analyses on the ostracod populations are proposed, in order to recognize which of the recorded environmental changes present a natural origin and which ones are caused by human activity.

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(*) Dr. Maria Eugenia Montenegro is a researcher at the Dipartimento di Scienze Geologiche, Marine e Ambientali of the University of Trieste, under the direction of the Director of the Department, Prof. Nevio Pugliese.

She has gained her considerable expertise in France and Italy. In the last few years she worked in Treiste in CNRS projects for the study and interpretation of samples from the Gulf of Thailand, and in Paris at the Laboratory of Physical Geography at the Université Pierre et Marie Curie, Paris VII on the modifications of the course of some Rhone's canals in the delta area, the origin of this modifications (natural or anthropic) and their consequences on the migrations of human settlements during the Middle Ages in delta of the Rhone river in France.

Dr. Montenegro has also worked at the University Pierre et Marie Curie, Paris VI on Climatic variability on the Bolivian Altiplano during the Holocene. The objective was to identify the ostracod populations of the Altiplano, its variations, and to realize geochemical analyses on their valves, in order to define the palaeoenvironmental sequence, the climatic changes and it consequences on the human settlements migrations in the Bolivian Altiplano during the Holocene.

During the period 1994 -1998 she was in Rome at the École Française d'Archeologie analyzing samples from the historic site of Aquileia, studying the ostracod fossil populations to understand the impact of the environmental changes on the human society and to define the origin of these changes. Simultaneously, in this period she worked at the University of Trieste on the study of ostracod populations in relation to the environmental changes.