T135 Paleoenvironmental Reconstructions from Biogenic Carbonates II

Monday, 5 November 2018
1:30 PM - 5:30 PM
Room 140

BIODIVERSITY AND DISTRIBUTION OF BENTHIC FORAMINIFERA IN HARRINGTON SOUND, BERMUDA: THE EFFECTS OF PHYSICAL AND GEOCHEMICAL FACTORS ON DOMINANT TAXA

Paper number: T135-13
Program: Technical Sessions
Time: 4:35 PM – 4:50 PM

Authors

Abstract

Harrington Sound, Bermuda, is a nearly enclosed lagoon acting as a subtropical/tropical, carbonate-rich basin in which carbonate sediments, reef patches, and carbonate-producing organisms accumulate. Here, one of the most important calcareous groups is the Foraminifera. Analyses of common benthic orders, including miliolids (Quinqueloculina and Triloculina spp.) and rotaliids (Homotrema rubrum, Elphidium spp., and Ammonia beccarii), are essential in understanding past and present environmental conditions affecting the island. These taxa have been studied previously; however, factors explaining their selective abundances in the sound are not well detailed. The goal of this study is to understand foraminiferal assemblage trends of these taxa by assessing parameters including depth, test-size, temperature, salinity, dissolved oxygen, pH, and variable interactions.

Benthic sediment samples were collected at depths ranging from 3 m to 24 m using an Ekman dredge, while water-quality data were collected using an In-Situ SMAR Troll MP probe. Due to the limited test-size of these taxa, samples < 1 mm and > 0.063 mm were examined. Dead-test and fragment counts were performed after randomizing sample selections with a sediment splitter. Using RStudio and ArcMap, basic, advanced statistical, and geospatial analyses were conducted on each taxon (segregated by test and fragment size) to examine depth-profile and spatial relationships between count data, physical, and geochemical factors.

Preliminary results from multiple quantile regression show that each taxon, under identical depth and spatial constraints, can be accounted for by different functional combinations of variables. In testing multivariate response and factorial influence, initial relative effect estimations and subset algorithms from nonparametric MANOVA effectively quantify abundance tendencies. Additionally, initial spatial maps allude to unexplored factors e.g. water influx from caves and outer reefs, visualizing the potential of hydrochemical influence in certain localities. The results of this study can serve as a baseline model for Neogene carbonate lagoons that accumulated Foraminifera under different climate conditions.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-318164

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