HIGH RESOLUTION SEISMIC STRATIGRAPHY IN EASTERN CONTINENTAL SHELF OF RIO GRANDE DO NORTE (NE OF BRAZIL)
Continental Shelf; Shallow seismic stratigraphy; Depositional systems; Boomer system
The mapping of subsurface features can contribute to the understanding the chronostratigraphic boundaries associated with distinct depositional phases, as well as to record the hydrodynamic conditions in the system. High resolution seismic, in this context, is widely used to delimitation of surfaces and structures allowing the understanding of the sedimentary evolution - its seismostratigraphy. The purpose of this study is to establish a relationship between the events and the chronostratigraphic boundaries associated with the sea level changes in the shelf during the Quaternary, in order to define the sedimentary evolution of the inner Continental Shelf adjacent to the city of Natal/RN. Thus, 31 lines (transversal and longitudinal) were distributed in 62 km along the inner shelf, using a boomer system that operates with energy of 300 J and frequency 1-2 kHz. The acquired data were later processed in the software ReflexWin 8.0, in which a flow processing was established that enhanced the seismic sections and the visualization of the reflectors. Through the analysis of the profiles, three main horizons, D01, D02 and D03, from bottom to top, respectively, representing the boundaries between the Seismic Units (U01, U02 and U03) were identified. The D01 horizon is represented by a large, discontinuous, high-amplitude sinuous surface that reaches 40 m depth and is located below Unit U01. The D02 horizon is an irregular, sometimes tabular, sometimes like depression surface that reaches 20 m deep. It is the boundary between Units U01 and U02. The horizon D03 is a parallel/subparallel surface that reaches up to 4 m deep and divides Units U02 and U03. Unit U01 has low continuity and frequency, varied amplitudes, and subparallel to chaotic configurations. The U02 Unit has high continuity, low frequency, moderate amplitude and configurations that range from parallels to sigmoidal clinoforms. The U01 and U02 are interpreted deposits developed in higher energy conditions. The U03 Unit features high continuity, low frequency, high amplitude and parallel configurations. This unit is interpreted as a depositional phase of lower energy. The D02 horizon represents an erosive surface that possibly represents the Pleistocene-Holocene chronostratigraphic boundary.