131 D12. Marine/Coastal Science

Wednesday, 28 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

USING INVASIVE AND NON-INVASIVE METHODS TO DETERMINE THE ORIGIN, EVOLUTION AND CLASSIFICATION OF COASTAL AEOLIAN MORPHOLOGIES

Paper number: 131-3
Program: Technical Sessions
Time: 1:50 PM – 2:00 PM

Authors

Abstract

Aeolian features framed as foredunes around the world, whose classification faces challenges to separate wave-formed from aeolian ridges, are hereby added to the context of anthropic influence. Morphologies previously classified as foredunes are arranged along the Brazilian northeastern coast. The pertinence of its classification as such, or even as truly developed dunes, was examined based on invasive and non-invasive methods. Detailed geomorphological mapping was performed through UAV and LiDAR surveying, as well as satellite imagery and aerial photographs multitemporal study. Ground Penetration Radar sections, trenches and particle size analysis were also done. The study area is composed by well-selected medium sand and strata varying predominantly from horizontal to low dip angle. Despite the obliquity of wind direction to the coastline, the main feature shows parallel positioning, conditioned by the exogenous vegetation placed about 60 meters from the high tide. The main body of this morphology showed practically no migration for over 15 years, however, wind breaks through the vegetation barrier to develop depositional lobes and hairpin-like crests protruding into the mainland. GPR sections reveal high dip angle cross strata sets on the base of only one aeolian sequence, preceding anthropogenic vegetation introduction. Low-angle thin subhorizontal layers anterior and posterior to that event cover this set. Sediments are characteristically aeolian and the internal cross-strata and morphology resembles protodunes. A similarity to foredunes early stages is also noticed, but without correlation between cross strata and morphologic stage. The complete disconnection of this aeolian morphology dynamics in the morphogenesis process also differentiates it from real foredunes. Before vegetation insertion, the area presented a wind dynamics different from the precedent scenario. This morphology, therefore, presents some aspects that are not characteristic to the classification of foredunes, nor common to the dunes naturally formed in the region, demanding a more adequate classification emphasizing its anthropogenic character.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-357234

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