The application of δ13C, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico

We assessed the use of δ13C, TOC and C/N values of bulk sedimentary organic matter (OM) to reconstruct paleoenvironmental and relative sea-level change from mangrove environments in Puerto Rico. The modern distribution of δ13C, TOC and C/N values was described from 63 vegetation and 59 surface sedim...

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Main Authors: Kendrick, Chris, Khan, Nicole Sophia, Horton, Benjamin Peter, Vane, Christopher H., Engelhart, Simon E.
Other Authors: Asian School of the Environment
Format: Article
Language:English
Published: 2019
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Online Access:https://hdl.handle.net/10356/105325
http://hdl.handle.net/10220/49528
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Institution: Nanyang Technological University
Language: English
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spelling sg-ntu-dr.10356-1053252020-09-26T21:27:35Z The application of δ13C, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico Kendrick, Chris Khan, Nicole Sophia Horton, Benjamin Peter Vane, Christopher H. Engelhart, Simon E. Asian School of the Environment Earth Observatory of Singapore Holocene Sea-level Reconstruction Social sciences::Geography We assessed the use of δ13C, TOC and C/N values of bulk sedimentary organic matter (OM) to reconstruct paleoenvironmental and relative sea-level change from mangrove environments in Puerto Rico. The modern distribution of δ13C, TOC and C/N values was described from 63 vegetation and 59 surface sediment samples collected from three sites containing basin and riverine mangrove stands, and was compared to microfossil (foraminiferal and thecamoebian) assemblages. Four vertically-zoned environments were identified: tidal flat (δ13C: −18.6 ± 2.8‰; TOC: 10.2 ± 5.7%; C/N: 12.7 ± 3.1), mangrove (δ13C: −26.4 ± 1.0‰; TOC: 33.9 ± 13.4%; C/N: 24.3 ± 6.2), brackish transition (δ13C: −28.8 ± 0.7‰; TOC: 40.8 ± 11.7%; C/N: 21.7 ± 3.7), and freshwater swamp (δ13C: −28.4 ± 0.4‰; TOC: 42.8 ± 4.8%; C/N: 17.0 ± 1.1). These environments had distinct δ13C, TOC and C/N values, with the exception of the brackish transition and freshwater swamp zones that were difficult to distinguish on a geochemical basis alone. The foraminiferal assemblages were complicated by a group that did not show a relationship to elevation due to the presence of calcareous foraminifera occurring above mean higher high water (MHHW), likely resulting from washover or transport by storms. However, the ratio of foraminifera to thecamoebians (F/T) along with δ13C, TOC and C/N values refines the distinction between brackish and freshwater environments. Using linear discriminant analysis, we applied the δ13C, TOC, C/N and F/T distributions to a 1.7 m core containing a continuous sequence of Rhizophora mangle peat, which began accumulating at ~1650–1930 CE. Together, microfossils, δ13C, TOC, and C/N values, and the core chronology from 137Cs and radiocarbon dating revealed that sediments in the core likely accumulated in response to anthropogenic sediment delivery, making it unsuitable for relative sea-level reconstruction. We caution that in the absence of detailed litho-, bio-, chemo-, or chrono-stratigraphic analyses as presented here, care should be taken in interpreting sea-level histories derived from single dates on mangrove peats. MOE (Min. of Education, S’pore) Published version 2019-08-05T04:52:59Z 2019-12-06T21:49:13Z 2019-08-05T04:52:59Z 2019-12-06T21:49:13Z 2019 Journal Article Khan, N. S., Vane, C. H., Engelhart, S. E., Kendrick, C., & Horton, B. P. (2019). The application of δ13C, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico. Marine Geology, 415, 105963-. doi:10.1016/j.margeo.2019.105963 0025-3227 https://hdl.handle.net/10356/105325 http://hdl.handle.net/10220/49528 10.1016/j.margeo.2019.105963 en Marine Geology © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/BY-NC-ND/4.0/). 22 p. application/pdf
institution Nanyang Technological University
building NTU Library
country Singapore
collection DR-NTU
language English
topic Holocene
Sea-level Reconstruction
Social sciences::Geography
spellingShingle Holocene
Sea-level Reconstruction
Social sciences::Geography
Kendrick, Chris
Khan, Nicole Sophia
Horton, Benjamin Peter
Vane, Christopher H.
Engelhart, Simon E.
The application of δ13C, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico
description We assessed the use of δ13C, TOC and C/N values of bulk sedimentary organic matter (OM) to reconstruct paleoenvironmental and relative sea-level change from mangrove environments in Puerto Rico. The modern distribution of δ13C, TOC and C/N values was described from 63 vegetation and 59 surface sediment samples collected from three sites containing basin and riverine mangrove stands, and was compared to microfossil (foraminiferal and thecamoebian) assemblages. Four vertically-zoned environments were identified: tidal flat (δ13C: −18.6 ± 2.8‰; TOC: 10.2 ± 5.7%; C/N: 12.7 ± 3.1), mangrove (δ13C: −26.4 ± 1.0‰; TOC: 33.9 ± 13.4%; C/N: 24.3 ± 6.2), brackish transition (δ13C: −28.8 ± 0.7‰; TOC: 40.8 ± 11.7%; C/N: 21.7 ± 3.7), and freshwater swamp (δ13C: −28.4 ± 0.4‰; TOC: 42.8 ± 4.8%; C/N: 17.0 ± 1.1). These environments had distinct δ13C, TOC and C/N values, with the exception of the brackish transition and freshwater swamp zones that were difficult to distinguish on a geochemical basis alone. The foraminiferal assemblages were complicated by a group that did not show a relationship to elevation due to the presence of calcareous foraminifera occurring above mean higher high water (MHHW), likely resulting from washover or transport by storms. However, the ratio of foraminifera to thecamoebians (F/T) along with δ13C, TOC and C/N values refines the distinction between brackish and freshwater environments. Using linear discriminant analysis, we applied the δ13C, TOC, C/N and F/T distributions to a 1.7 m core containing a continuous sequence of Rhizophora mangle peat, which began accumulating at ~1650–1930 CE. Together, microfossils, δ13C, TOC, and C/N values, and the core chronology from 137Cs and radiocarbon dating revealed that sediments in the core likely accumulated in response to anthropogenic sediment delivery, making it unsuitable for relative sea-level reconstruction. We caution that in the absence of detailed litho-, bio-, chemo-, or chrono-stratigraphic analyses as presented here, care should be taken in interpreting sea-level histories derived from single dates on mangrove peats.
author2 Asian School of the Environment
author_facet Asian School of the Environment
Kendrick, Chris
Khan, Nicole Sophia
Horton, Benjamin Peter
Vane, Christopher H.
Engelhart, Simon E.
format Article
author Kendrick, Chris
Khan, Nicole Sophia
Horton, Benjamin Peter
Vane, Christopher H.
Engelhart, Simon E.
author_sort Kendrick, Chris
title The application of δ13C, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico
title_short The application of δ13C, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico
title_full The application of δ13C, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico
title_fullStr The application of δ13C, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico
title_full_unstemmed The application of δ13C, TOC and C/N geochemistry of mangrove sediments to reconstruct Holocene paleoenvironments and relative sea levels, Puerto Rico
title_sort application of δ13c, toc and c/n geochemistry of mangrove sediments to reconstruct holocene paleoenvironments and relative sea levels, puerto rico
publishDate 2019
url https://hdl.handle.net/10356/105325
http://hdl.handle.net/10220/49528
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