Contribuição ao estudo da Geologia do território federal do Amapá

Abstract

            The author, Prof. Antônio Teixeira Guerra, studies in this paper, the geological formations found in the Territory of Amapá.

            At first, the author describes the difficulties of transport in the region, chiefly due to the existence of the Amazonian forest and to the lack of communications. His study had to be made, because of those conditions, along the rivers, in its major part.

            The geologic succession, in the Territory is represented through formations that vary from the most ancient age - arquean - to the most recent - holocene.

            There exists, though, an empty space in what concerns to the stratigraphy: from the silurian to the pliocene, or possibly to the beginning of the quaternary. Besides this, there is another point on which information is lacking: from the end of the algonquian to the beginning of the silurian. So, considering the above said statements, the following terrains remain unobserved in the geological succession of the Territory: base of the Paleozoic - carboniferous and permian, the whole mesozoic and possibly the whole tertiary.

            The author studies in detail each of the formations of the stratigraphy observed in the Territory: 1) arquean terrains - comprising a vast area of the Guyana shield; 2) algonquian terrains - represented by localized areas, discovered by the geologist Fritz Ackerman; 3) silurian and devonian terrains - represented by some areas in the south of the Territory; 4) quaternary terrains - composed of recent sediments which form a belt along the older terrains.

            The author emphasizes that many of his ideas are based in geological and geomorphological concepts, and states that those ideas constitute hypotheses to be confirmed by further research in the field.

            By ending his paper, the author distinguishes two geological regions or provinces in the Territory of Amapá: 1) the region of the crystalline shield, chiefly composed by eruptive rocks and by rocks which resulted of transformation of pre-existing ones - metamorphic and sedimentary; 2) sedimentary region, composed of terrains which age ranges from the algonquian to the holocene.