Recognising subtidal foraminiferal assemblages: implications for quantitative sea-level reconstructions using a foraminifera-based transfer function

2009 ◽  
Vol 24 (3) ◽  
pp. 215-223 ◽  
Author(s):  
Sarah A. Woodroffe
Keyword(s):  
Transfer Function ◽  
Sea Level

FORAMINIFERAL TRANSFER FUNCTION FOR HIGH-RESOLUTION SEA-LEVEL RECONSTRUCTION DURING HOLOCENE IN SUNDA SHELF, OFF MALAYSIA WATERS

2020 ◽  
Author(s):  
Fatin Izzati Minhat ◽  
◽  
Nazihah Azmi ◽  
Nazihah Azmi ◽  
Nur Hidayah Roseli ◽  
...  
Keyword(s):  
High Resolution ◽  
Transfer Function ◽  
Sea Level ◽  
Sunda Shelf

A FORAMINIFERAL-BASED TRANSFER FUNCTION: IMPLICATIONS FOR SEA-LEVEL STUDIES

1999 ◽  
Vol 29 (2) ◽  
pp. 117-129 ◽  
Author(s):  
B. P. Horton ◽  
R. J. Edwards ◽  
J. M. Lloyd
Keyword(s):  
Transfer Function ◽  
Sea Level

scholarly journals Minimal stratigraphic evidence for coseismic coastal subsidence during 2000 yr of megathrust earthquakes at the central Cascadia subduction zone

Geosphere ◽  
2020 ◽  
Author(s):  
Alan R. Nelson ◽  
Andrea D. Hawkes ◽  
Yuki Sawai ◽  
Ben P. Horton ◽  
Rob C. Witter ◽  
...  
Keyword(s):  
Transfer Function ◽  
Sea Level ◽  
Function Analysis ◽  
Detection Threshold ◽  
Cascadia Subduction Zone ◽  
Tsunami Deposit ◽  
Diatom Assemblages ◽  
14C Dating ◽  
Megathrust Earthquakes ◽  
Transfer Function Analysis

Lithology and microfossil biostratigraphy beneath the marshes of a central Oregon estuary limit geophysical models of Cascadia megathrust rupture during successive earthquakes by ruling out >0.5 m of coseismic coastal subsidence for the past 2000 yr. Although the stratigraphy in cores and outcrops includes as many as 12 peat-mud contacts, like those commonly inferred to record sub­sidence during megathrust earthquakes, mapping, qualitative diatom analysis, foraminiferal transfer function analysis, and 14C dating of the contacts failed to confirm that any contacts formed through subsidence during great earthquakes. Based on the youngest peat-mud contact’s distinctness, >400 m distribution, ∼0.6 m depth, and overlying probable tsunami deposit, we attribute it to the great 1700 CE Cascadia earthquake and(or) its accompanying tsunami. Minimal changes in diatom assemblages from below the contact to above its probable tsunami deposit suggest that the lower of several foraminiferal transfer function reconstructions of coseismic subsidence across the contact (0.1–0.5 m) is most accurate. The more limited stratigraphic extent and minimal changes in lithology, foraminifera, and(or) diatom assemblages across the other 11 peat-mud contacts are insufficient to distinguish them from contacts formed through small, gradual, or localized changes in tide levels during river floods, storm surges, and gradual sea-level rise. Although no data preclude any contacts from being synchronous with a megathrust earthquake, the evidence is equally consistent with all contacts recording relative sea-level changes below the ∼0.5 m detection threshold for distinguishing coseismic from nonseismic changes.

Assessing sea-level data from Connecticut, USA, using a foraminiferal transfer function for tide level

2004 ◽  
Vol 51 (3-4) ◽  
pp. 239-255 ◽  
Author(s):  
R.J Edwards ◽  
O van de Plassche ◽  
W.R Gehrels ◽  
A.J Wright
Keyword(s):  
Transfer Function ◽  
Sea Level ◽  
Level Data ◽  
Tide Level

Assessing the performance of a foraminifera-based transfer function to estimate sea-level changes in northern Portugal

2011 ◽  
Vol 75 (1) ◽  
pp. 278-287 ◽  
Author(s):  
Eduardo Leorri ◽  
Francisco Fatela ◽  
Alejandro Cearreta ◽  
João Moreno ◽  
Carlos Antunes ◽  
...  
Keyword(s):  
Transfer Function ◽  
Sea Level ◽  
Cross Validation ◽  
Compositional Data ◽  
Depositional Environments ◽  
Sea Level Changes ◽  
Concentration Data ◽  
Data Set ◽  
Northern Portugal ◽  
The Impact

AbstractWe assessed the performance of a transfer function model for sea-level studies using salt-marsh foraminifera from two estuaries of northern Portugal. An independent data set of 12 samples and 13 sub-fossil samples from a core were used to evaluate if reconstructions and errors derived from current models are adequate. Initial transfer function models provided very strong results as indicated by cross-validation (component 2; r2 = 0.80–0.82; RMSEP ranged from 10.7 to 12.3 cm) and improved its performance by ca. 10% when sample size reached ca. 50. Results derived using an independent test data set indicate that cross-validation is a very effective approach and produces conservative errors when compared to observed errors. We additionally explored the possible effect of transforming the concentration data into percent in the error estimations by comparing the results obtained based on the use of both concentration and compositional data. Results indicate that this type of transformation does not affect the performance of the transfer function. Results derived from a reconstruction of sub-fossil samples from a core indicate that high-resolution sea-level reconstructions are possible, but show that depositional environments have to be selected carefully in order to minimize the impact of possible taphonomical loss.

Enough is Enough, or More is More? Testing the Influence of Foraminiferal Count Size on Reconstructions of Paleo-Marsh Elevation

2020 ◽  
Vol 50 (3) ◽  
pp. 266-278
Author(s):  
Andrew C. Kemp ◽  
Alexander J. Wright ◽  
Niamh Cahill
Keyword(s):  
Salt Marsh ◽  
Transfer Function ◽  
Sea Level ◽  
Transfer Functions ◽  
Regional Scale ◽  
Weighted Averaging ◽  
Additional Time ◽  
Modest Improvement ◽  
Large Numbers ◽  
Decadal Scale

ABSTRACT Salt-marsh foraminifera are sea-level proxies used to quantitatively reconstruct Holocene paleo-marsh elevations (PME) and subsequently relative sea level (RSL). The reliability of these reconstructions is partly dependent upon counting enough foraminifera to accurately characterize assemblages, while counting fewer tests allows more samples to be processed. We test the influence of count size on PME reconstructions by repeatedly subsampling foraminiferal assemblages preserved in a core of salt-marsh peat (from Newfoundland, Canada) with unusually large counts (up to 1595). Application of a single, weighted-averaging transfer function developed from a regional-scale modern training set to these ecologically-plausible simulated assemblages generated PME reconstructions at count sizes of 10–700. Reconstructed PMEs stabilize at counts sizes greater than ∼50 and counts exceeding ∼250 tests show little return for the additional time invested. The absence of some rare taxa in low counts is unlikely to markedly influence results from weighted-averaging transfer functions. Subsampling of modern foraminifera indicates that cross-validated transfer function performance shows only modest improvement when more than ∼40 foraminifera are counted. Studies seeking to understand multi-meter and millennial scale RSL trends should count more than ∼50 tests. The precision sought by studies aiming to resolve decimeter- and decadal-scale RSL variability is best achieved with counts greater than ∼75. In most studies seeking to reconstruct PME, effort is more productively allocated by counting relatively fewer foraminifera in more core samples than in counting large numbers of individuals. Target count sizes of 100–300 in existing studies are likely conservative and robust. Given the low diversity of salt-marsh foraminiferal assemblages, our results are likely applicable throughout and beyond northeastern North America.

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