147-16 The Response of Deep-sea Benthic Foraminifera to Variations in Terrigenous Input on the Continental Slope, Southwest Atlantic.

Session: Climate, Ocean and Environmental Changes Through Earth History: From Marine and Terrestrial Proxies to Model Assessments (Posters)

Poster Booth No.: 183

Presenting Author:

Fabiana de Almeida

Authors:

de Almeida, Fabiana K.¹, Rodrigues, André R.², de Mello, Renata M.³, Leite, Jordan S.S.⁴, Jardim, Kerly A.⁵, Millo, Christian⁶, Quaresma, Valéria S.⁷, Bastos, Alex C.⁸

(1) Laboratory of Marine Geosciences (LaboGeo), Postgraduate Program in Environmental Oceanography, Department of Oceanography and Ecology, Universidade Federal do Espírito Santo, Vitoria, ES, Brazil, (2) Laboratory of Marine Geosciences (LaboGeo), Postgraduate Program in Environmental Oceanography, Department of Oceanography and Ecology, Universidade Federal do Espírito Santo, Vitoria, ES, Brazil, (3) Petrobras S.A, Rio de Janeiro, RJ, Brazil, (4) Laboratory of Marine Geosciences (LaboGeo), Postgraduate Program in Environmental Oceanography, Department of Oceanography and Ecology, Universidade Federal do Espírito Santo, Vitoria, ES, Brazil, (5) Laboratory of Marine Geosciences (LaboGeo), Postgraduate Program in Environmental Oceanography, Department of Oceanography and Ecology, Universidade Federal do Espírito Santo, Vitoria, ES, Brazil, (6) Oceanographic Institute, Universidade de São Paulo, São Paulo, SP, Brazil, (7) 1 Laboratory of Marine Geosciences (LaboGeo), Postgraduate Program in Environmental Oceanography, Department of Oceanography and Ecology, Universidade Federal do Espírito Santo, Vitoria, ES, Brazil, (8) Laboratory of Marine Geosciences (LaboGeo), Postgraduate Program in Environmental Oceanography, Department of Oceanography and Ecology, Universidade Federal do Espírito Santo, Vitoria, ES, Brazil,

Abstract:

This study aims to investigate the response of deep-sea benthic foraminifera to an intense terrigenous input on the continental slope. The vertical variability of benthic foraminiferal assemblages (> 63µm) was analysed in two piston cores from the Espírito Santo Basin slope (ESB, southeastern Brazilian Continental Margin, 1128 to 2093 m water depth), along with vertical profiles of δ¹⁸O values of Cibicidoides wuellerstorfi, sediment type and grain size, carbonate content (%CaCO₃), and XRF. The analysed interval recorded the last 106.6 kyr B.P, including the Marine Isotope Stages (MIS) 5 to 1. Two major periods of environmental changes were identified:  1) From 106.6 to 16.9 kyr B.P. (MIS 5 to 2) there was predominance of mixed sediments (median CaCO₃ = 28%) with minimal terrigenous input and a median sedimentation rate from 8.5 to 6.7 cm/kyr; 2) from 12 to 8.9 kyr B.P. (MIS 1), a remarkable influx of terrigenous material (median CaCO₃ = 7%) took place, with a median sedimentation rate that fluctuated between 69.9 and 64.5 cm/kyr. During this terrigenous influx, Fe/Ca and Ti/Ca ratios increased significantly within a distinct orange-red mud layer. The terrigenous input was also marked by a significant change in benthic foraminiferal density, a decrease in species richness and in the planktic/benthic ratio, accompanied by an increase in the relative abundance of infaunal species from the genera Bolivina (i.e., B. paula and B. lowmani) and Bulimina (i.e., B. aculeata and B. marginata). Our results suggest that these species coped with the change in sedimentary conditions from 12 to 8.9 kyr B.P. Conversely, species from the genera Globocassidulina (i.e., G. crassa, G. rossensis and G. subglobosa), the epifaunal species Discorbis vilardeboanus, Epistominella exigua and Alabaminella weddellensis increased in abundance during the intervals of predominant mixed sedimentation. Our results underscore the importance of combining microfaunal data to sedimentological and geochemical information to better reconstruct the environmental changes trigged by intense terrigenous input on continental slopes.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7189

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