POST-EVENT FIELD TRIP
Cretaceous and Neogene deposits of the northern Brazilian Amazon: fluvial progradation over a carbonate platform
The field trip area is in the transition zone between the Amazon Craton and the Equatorial Brazilian coastal basins of the North Atlantic Ocean, whose evolution occurred since the Upper Jurassic with the most important events in Cretaceous and Cenozoic. The onshore portion of Northern Brazilian coast is represented by several basins and platforms that were the main sites of carbonate deposition. They are filled with a thick sediment pile reaching 6 kilometers, deposited in onshore and offshore areas, forming large platforms of passive margin strongly influenced by fluvial progradation and sea level changes. Pirabas, Barreiras and Post-Barreiras deposits represent the main units of the stratigraphic framework of the Bragantina Platform. The Pirabas Formation consists of carbonate and siliciclastic deposits related to the onshore portion of a shallow marine platform. The inner platform is composed of tidal flats and lagoonal deposits. Tidal inlets and bioclastic barrier front shoal deposits constitute the inner/middle platform setting. Tidal inlet deposits are characterized by wackestone/packstone with bryozoans, and grainstone with low-angle cross stratification containing foraminifers and red algae. The sedimentary record of the Barreiras Formation consists mostly of highly weathered structureless mudrocks and sandstones and, more rarely, conglomerates formed in a variety of environments, ranging from alluvial fan and fluvial to estuarine. The best exposures of these rocks occur along coastal cliffs, as well as on few road cuts and quarries. The top of the Barreiras Formation is characterized by an unconformity with erosional relief of several meters at outcrop scale. This unconformity is marked by vertical columns of ferruginous concretions related to a lateritic paleosol of regional expression.
Itinerary:
Day 1 – Belém – Salinas: Outcrops of fossiliferous carbonate platforms and fluvial deposits at road cuts and cliffs.
Day 2 – Salinas – Santa Izabel – Castanhal: Alluvial and fluvial deposits, lateritic paleosol bounding Neogene deposits and unconsolidated Quaternary fluvial sediments.
Day 3 – Belém – Outeiro – Mosqueiro: Kilometer-scale cliffs with fluvial deposits of the Barreiras Formation.
Day 4 (optional) – Immersive experience at an Amazon island in Belém (Combu Island) and regional gastronomy.
Date: August, 02, 03 and 04 (after event)
Number of participants: 10 (minimum) – 20 (maximum)
Coast: 450 euros (the coast includes: transport by bus, accommodation and field trip leader).
Leader: Afonso César Rodrigues Nogueira (UFPA)
