Suitability of inter-tidal benthic foraminifera as proxy

0 downloads 0 Views 889KB Size Report
precise reconstructions (RMSEPjack = 0.12 in WA-PLS and 0.10 m in PLS). The ... from contemporary surface sediment and a 2.25 m long sediment core,.
Suitability of inter-tidal benthic foraminifera as proxy indicators of sea-level in Al-Kharrar Lagoon, Saudi Arabia Talha A. Al-Dubai

1, 2

1

, Ramadan H. Abu-Zied and Ali S. Basaham

1

1

Marine Geology Department, Faculty of Marine Science, KAU, Jeddah, SA 2 Marine Geology Department, Faculty of Marine Science and Environments, Hodeidah University, Hodeidah, Yemen. E-mail: [email protected]

Abstract

Introduction

A transfer function for past sea-level reconstructed from a dataset consisting of 75

Al-Kharrar Lagoon is located 10 km northwest Rabigh City on the Red Sea. It oc-

contemporary foraminiferal samples and 111 species using Averaging-Partial-Least

curs in warm, arid region and it is a shallow (mean ~5 m depth) small basin that

Squares (WA-PLS) and Partial-Least Squares (PLS) regressions. The performance of

connected with the Red Sea water via a very narrow inlet (c. 120 m wide and 14

the transfer function illustrates a strong relationship between observed and foraminif-

m deep) (Al-Dubai et al., 2017). Its ecology is strongly influenced by local mete-

0.80 in WA-PLS and 0.88 in PLS) with relatively

orological conditions (Abu-Zied and Bantan, 2013). Thus, it is a sensitive basin for

precise reconstructions (RMSEPjack = 0.12 in WA-PLS and 0.10 m in PLS). The

both climatic and environmental changes. Reconstruction of past sea-level chang-

transfer function models produced good statistical parameters in terms small errors

es of the Red Sea coastal lagoons during late Holocene based mainly on an inter-

(RMSEP) and highest squared correlation values r² jack) in both models WA-PLS and

tidal benthic foraminifera is rare. Therefore, in this study, we present results

PLS, indicating that reliable reconstructions of palaeo-tidal elevations using training

from contemporary surface sediment and a 2.25 m long sediment core,

datasets are possible in the lagoon.

KHAR2, taken from the intertidal zone of the Al-Kharrar Lagoon.

era-predicted elevation (r²

jack =

Materials and Method The development of a foraminiferal-based transfer function Modern benthic foraminifera “training set” (111 species and 75 sediment samples), environmental parameters such as (Temperature, salinity and depth).

Q. What is the transfer functions? 

Regression models



Weighted Average Partial Least Squares (WA-PLS).



Partial Least Squares (PLS).



The assessment of transfer functions models was based on:

Root-mean square error of prediction (RMSEP) and squared correlation (r2).

Results and Discussion Sample elevations predicted by the WA-PLS (a) and PLS (c) regression models, compared with observed elevations. Model

Training data set

Training data set

method No. of sample No. of species Component

WA-PLS 75 111 1

2

3

PLS 75 111 1

2

3

RMSE (m) r² Max Bias (m) r² (jack)

0.13 0.78 0.15 0.58

0.09 0.90 0.07 0.74

0.06 0.95 0.08 0.80

0.12 0.82 0.13 0.72

0.08 0.92 0.10 0.83

0.06 0.95 0.07 0.88

Max Bias (jack, m) RMSEP (m)

0.30 0.18

0.21 0.14

0.14 0.12

0.20 0.15

0.14 0.11

0.13 0.10

The significant used values RMSEP (jack), r² (jack) and components that are highlighted in bold characters.

A comparison between our results about the precision of models (WA-PLS and PLS) in the present study with other areas in the world. Site

N

Model

RMSEP jack (m)

Mean tidal range (m)

Reference

Central Red Sea, Al-Kharrar Lagoon Central Red Sea coast, Al-Kharrar Lagoon

75 75 29 43 43 46

WA-PLS PLS WA-PLS WA-PLS PLS WA-PLS

0.12 0.10 0.16 0.10 0.09 0.04

0.24 0.24 0.25 0.60 0.60 0.27

The present study The present study Abu-Zied and Bantan (2013) Callard et al. (2011) Callard et al. (2011) Kemp et al. (2009)

91

WA-PLS

0.20

1.81

Hawkes et al. (2010)

22 91 30 46 43

PLS WA-PLS WA-PLS WA-PLS PLS

0.14 0.18 0.19 0.27 0.22

2.00 1.36 2.50 2.5 2.59

Leorri et al. (2010) Edwards et al. (2004) Leorri et al. (2008a) Leorri et al. (2008b) Leorri et al. (2010)

85

WA-PLS

0.29

3.45

Massey et al. (2006)

W Red Sea coast, Shuaiba Lagoon SW Pacific Tasmania SW Pacific Tasmania N Carolina, USA (average of 3 locations) NE Pacific Oregon (average of 5 locations) S Portugal Connecticut, USA (average of 4 locations)

N Spain (average of 4 locations) Southern Bay of Biscay Brittany, France E Atlantic S England (average of 2 locations)

Conclusions

Acknowledgements

References

Inter-tidal benthic foraminifera from the

The authors are thankful to Mr. Fikry

Abu-Zied, R. H. and Bantan, R. A. (2013) Hypersaline benthic foraminifera:

Al-Kharrar Lagoon sediments are suita-

Shaher, Mr. Aaid alqadri, Mr. Ahmed

Their environmental controls and usefulness in sea level reconstruction at the

bility tool to reconstructing of former sea

Taqi, and Mr. Satria Antoni for their

Shuaiba Lagoon, eastern Red Sea, Saudi Arabia. Marine Micropaleontology 103: 51–

-level changes using the transfer function

assistance in the fieldwork.

67.

Talha Ahmed Al-Dubai Research Fellow-Marine Geology — KAU 00966-508537472 [email protected]