Abstract

Knowledge of the Devonian sequence of the Amazonas basin has profited greatly from the oil-exploration work conducted by “Petroleo Brasileiro S.A., Petrobras” since 1955. These advances are particularly gratifying because the region is relatively remote and access to outcrop is very much restricted. Unsolved problems remain, particularily:

1) The exact nature of palaeogeographic relations of the Amazon Devonian formations and faunas to those of the neighbouring sedimentary basins (Parnaiba and Parana basins in Brazil, Andean trough in Bolivia). In the Amazon Devonian “boreal” (= Appalachian) elements are dominant; but the associated minority of malvinocaffric elements deserves special interest. New information from neighbouring basins, especially Bolivia, might lead to a clearer understanding of the age-relationship of the Amazon Devonian.

2) The correlation with the New York—Appalachian succession. Correlations suggested vary from Lower to Middle and even to Upper Devonian.

The various uncertainties follow from two main difficulties. Firstly, the peculiarities of the faunas, which lack some important palaeontological groups (e.g. goniatites), and have only poor representations of others (e.g. trilobites and conodonts, which do, nevertheless, hold much promise as stratigraphical tools). Secondly, the present inadequate state of sampling: (in spite of the recent accessions of new data). Exhaustive collections from well-defined and well-located outcropping horizons are still much in need. Until these are available, there can be no fully secure basis for discussion of the remaining problems.