A new procedure to assess dissolution based on experiments on Pliocene-Quaternary Foraminifera (ODP Leg 160, Eratosthenes Seamount, eastern Mediterranean)

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doi: 10.1016/j.marmicro.2013.11.004
Author(s): Thi Minh Phuong Nguyen; Speijer, Robert P.
Author Affiliation(s): Primary:
Duy Tan University, Research Center for Science and Technology, Danang, Vietnam
Other:
Katholieke Universiteit Leuven, Belgium
Volume Title: Marine Micropaleontology
Source: Marine Micropaleontology, Vol.106, p.22-39. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0377-8398 CODEN: MAMIDH
Note: In English. Includes appendix. 74 refs.; illus., incl. strat. cols., 2 tables, sketch map
Summary: This study aims to reveal the effects of differential dissolution on the quantitative composition of foraminiferal assemblages. Through this, we develop a procedure to evaluate dissolution in foraminiferal assemblages in order to reduce taphonomic bias in paleoenvironmental reconstructions. To achieve this, we carried out experimental dissolution studies on foraminiferal assemblages from Pliocene-Quaternary sapropel-bearing sequences of Eratosthenes Seamount, Eastern Mediterranean (ODP Leg 160, Site 966). Our experiments refine two general observations on modern foraminifera, which are in fact only applicable for size fraction of 125-630µm: 1) Dissolution increases the relative abundance of fragmentation in planktic assemblages (%Fp) more rapidly than in benthic assemblages (%Fb); 2) with moderate to severe dissolution, planktic foraminiferal numbers decrease faster than benthic foraminiferal numbers. Besides, our experiments show that dissolution susceptibility differs between architectural types. As dissolution progresses, the proportions of uniloculars, uniserials, biserials, then tri-multiserials and miliolines gradually decrease and benthic foraminiferal assemblages become relatively enriched in planispirals and trochospirals. These findings allow re-evaluation of commonly used foraminiferal dissolution indices. Accordingly, %F can be used to assess dissolution in weakly to moderately dissolved planktic assemblages (size fraction >125µm) in non-lithified sediments; P/B ratios are a better indicator of dissolution in moderately to severely dissolved assemblages, but only in the size fraction >125µm and not in the smaller size fraction. Anomalously low foraminiferal numbers (compared to background numbers in a sequence) can also hint at dissolution. A dominance of planispiral, trochospiral and large taxa in benthic assemblages may be used as an additional dissolution indicator. Based on these results, we propose a new procedure to evaluate dissolution in foraminiferal assemblages. Application of this procedure to some published Pliocene-Quaternary records reveals a good agreement between our experiments and expected consequences of dissolution for these records. In order to achieve more robust interpretations based on quantitative foraminiferal data, the dissolution procedure proposed should be tested elsewhere and could develop into a standard micropaleontologic procedure. This is useful in not only open ocean records, but also continental margin studies dealing with major biotic events or studies employing P/B ratios for sea-level reconstructions are expected to benefit from this approach. Abstract Copyright (2014) Elsevier, B.V.
Year of Publication: 2014
Research Program: ODP Ocean Drilling Program
Key Words: 10 Paleontology, Invertebrate; Cenozoic; East Mediterranean; Eratosthenes Seamount; Experimental studies; Faunal studies; Foraminifera; Invertebrata; Japan Sea; Laboratory studies; Leg 128; Leg 160; Levantine Basin; Lithostratigraphy; Mediterranean Sea; Methods; Microfossils; Morphology; Neogene; North Pacific; Northwest Pacific; ODP Site 798; ODP Site 799; ODP Site 966; Ocean Drilling Program; Oki Ridge; Pacific Ocean; Pliocene; Preservation; Protista; Quantitative analysis; Quaternary; Solution; Taphonomy; Tertiary; Tests; West Pacific; Yamato Rise
Coordinates: N370218 N391314 E1344759 E1335200
N334748 N334748 E0324205 E0324205
Record ID: 2014019775
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands