Taphonomy of the foraminifera of the Pirabas Formation (Lower Miocene), State of Pará.

Abstract

This paper deals with taphonomy of the foraminifera from the Pirabas Formation, collected in one outcrop and four drillings executed in the Maracanã, Bragança and Capanema districts, northeastern Pará State. The recognized species belong to the Ammonia beccarii association, of shallow lagoonal environment with calcareous and fine substratum. They show moderate degree of fragmentation, ineffective abrasion, three stages of dissolution and bio-erosion by filamentous algae and microbes. The association defines the transport group II, show evidences of bed load transport and is located in the field I of the alteration degree, due to the preservation of 70% of original association, and may be framed in the field of Tafofacies I. The paleo-environment is lagoonal, eutrophic, with variations in salinity, bathimetry, basal relief and substratum hardness, with small fluctuations of the sea level and communication to open sea, according with Amphistegina, Archaias, Cibicides and the planktonic taxa. The taphonomic data attest high level of energy of environment during the burial event, associated with storm waves.