Spatiotemporal Δ17O variability in the rock record

2020 ◽  
Author(s):  
Matthew Warke ◽  
Ross Pettigrew ◽  
David Millward ◽  
Robert Raine ◽  
Stuart Clarke ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Coastal Wetland ◽  
Sulfide Oxidation ◽  
Depositional Environments ◽  
Atmospheric Composition ◽  
Spatiotemporal Variability ◽  
Rift Basins ◽  
Margin Setting ◽  
Coastal Sabkha

<p>The  Δ<sup>17</sup>O value of sedimentary sulfate can provide a direct, stable, geological archive of atmospheric-biospheric evolution. Negative Δ<sup>17</sup>O values in gypsum/anhydrite are inherited from the negative Δ<sup>17</sup>O value of atmospheric O<sub>2</sub> which is transferred to sulfate during sulfide weathering. The magnitude of the O<sub>2</sub> Δ<sup>17</sup>O value reflects pCO<sub>2</sub>, pO<sub>2</sub> and gross primary productivity, hence modelling of the geological Δ<sup>17</sup>O record has led to estimates of changing atmospheric composition and primary productivity over Earth history. However, sulfate Δ<sup>17</sup>O values represent a conservative estimate of atmospheric Δ<sup>17</sup>O values as the magnitude of negative Δ<sup>17</sup>O in sulfate can be diluted (or erased) through sulfur cycling. As sulfate is transported away from the site of sulfide oxidation the likelihood of this happening increases.</p><p>Although this effect is acknowledged, the extent to which Δ<sup>17</sup>O values may vary within and between palaeoenvironments, and how evaporite sedimentology may affect stratigraphic interpretations of Δ<sup>17</sup>O values, remains unclear. We present the preliminary results of two case-studies probing the spatiotemporal variability of Δ<sup>17</sup>O values.</p><p>Case-study 1: temporally correlative Tournaisian (Lower Mississippian) evaporites within Carboniferous rift basins of Britain and Ireland were deposited in a range of settings: coastal wetland (Ballagan Fm.); supratidal sabkha on margin of a restricted basin (Ballycultra Fm.); and coastal sabkha on open ocean margin (Middleton Dale Anhydrite Fm.) All three settings plot on a positive slope in d<sup>34</sup>S vs Δ<sup>17</sup>O space with values ranging between δ<sup>34</sup>S ≈ +15 ‰, Δ<sup>17</sup>O ≈ -0.08 ‰ and δ<sup>34</sup>S ≈ +24 ‰, Δ<sup>17</sup>O ≈ -0.2 ‰. We discuss whether this trend (and intraformational trends) represents a spatial variability in sulfate Δ<sup>17</sup>O as controlled by fluctuating fluvial and marine dominance in evaporite depositional environments, or whether this might represent a temporal change in δ<sup>34</sup>S and Δ<sup>17</sup>O.   </p><p>Case study 2: non-marine evaporites of the early Permian Cedar Mesa Sandstone (CMS) Formation in Utah were deposited in continental saline pans in an erg-margin setting that fluctuated through arid and humid cycles. These evaporites record negative Δ<sup>17</sup>O values as low as -270 per meg, however δ<sup>34</sup>S values lie along the marine curve. We interpret the signal preserved in the CMS as recycling of the underlying marine evaporites of the late Carboniferous Paradox Formation which have been uplifted on the basin margin. Hence, we discuss how in non-marine settings the recycling of evaporites can decouple the age of the succession from the age of the atmospheric Δ<sup>17</sup>O signal.</p>

Spatiotemporal variability of vegetation due to drought dynamics (2012–2017): a case study of the Upper Paraíba River basin, Brazil

2020 ◽  
Vol 102 (3) ◽  
pp. 939-964
Author(s):  
Glauciene Justino Ferreira da Silva ◽  
Nádja Melo de Oliveira ◽  
Celso Augusto Guimarães Santos ◽  
Richarde Marques da Silva
Keyword(s):  
River Basin ◽  
Spatiotemporal Variability

scholarly journals Short‐term variability in euphotic zone biogeochemistry and primary productivity at Station ALOHA: A case study of summer 2012

2015 ◽  
Vol 29 (8) ◽  
pp. 1145-1164 ◽  
Author(s):  
Samuel T. Wilson ◽  
Benedetto Barone ◽  
Francois Ascani ◽  
Robert R. Bidigare ◽  
Matthew J. Church ◽  
...  
Keyword(s):  
Primary Productivity ◽  
Euphotic Zone ◽  
Short Term ◽  
Station Aloha ◽  
Short Term Variability

Sedimentology and Evolution of the Fluvial-Deltaic System: A Modern Depositional Model Analog from the Red Sea Coastal Region, Saudi Arabia

2021 ◽  
Author(s):  
Osman Abdullatif ◽  
Mutasim Osman ◽  
Mazin Bashri ◽  
Ammar Abdlmutalib ◽  
Mohamed Yassin
Keyword(s):  
Red Sea ◽  
Coastal Plain ◽  
Depositional Environments ◽  
Hydrocarbon Reservoirs ◽  
Sediment Supply ◽  
Arabian Shield ◽  
Space And Time ◽  
Groundwater Aquifers ◽  
Coastal Sabkha ◽  
Lithofacies Association

Abstract Siliciclastic sediments represent important lithological unit of the Red Sea coastal plain. Their subsurface equivalents are important targets of groundwater aquifer and hydrocarbon reservoirs in the region. The lithofacies of the modern fluvial deltaic system has several distinct geomorphic units and sub-environments such as alluvial, fluvial, delta plain, aeolian, intertidal, coastal sabkha and eustuarine sediments. This study intends to characterize the lithofacies and the depositional environments and to produce an integrated facies model for this modern fluvial-deltaic system. The study might provide a valuable modern analog to several important subsurface Neogene formations that act as important hydrocarbon reservoirs and groundwater aquifers. The study integrates information and data obtained from landsats, maps and detailed field observation and measurements of facies analysis of the fluvial and deltaic along traveses from the Arabian Shield to the Red Sea coast. The lithofacies sediment analysis revealed four main lithofacies associations namely lithofacies A,B,C ad D. Lithoacies Associations A, which represents the oldest unit is dominated by coarse gravel with minor sands facies. While the lithofacies B is dominated byfine gravel and sand lithofacies, occasionally pebbly, vary from horizontal, planar to massive sands with minor laminated to massive silts and mud facies. The lithofacies in A and B show lateral proximal to distal variation as well as characteristic vertical stacking patterns. The Facies Association A and B indicates a change in fluvial depositional styles from gravelly alluvial fans to gravelly sandy fluvial systems. The lithofacies association C represents the recent fluvial system which consists of minor gravel lag deposits associated maily with various sand lithofacies of planner, horizontal and massive sand associated with massive and limainted sand and mud lithofacies. The lithofacies Association D is dominated with Barchan sand dunes local interfigger with muddy iinterdunes and sand sheets. Lithofacies D occupies rather more distal geomporphic position of the fluvial deltaic system that is adjace to coastal sabkha. The lithofacies associations described here document the evolution and development of the coastal plain sediments through space and time under various autocyclic and allocyclic controls. This included the tectonics and structural development associated with the Red Sea rifting and opening since the Oligocene – Miocene time. Others controls include the evolution of the Arabian shield (provenance) and the coastal plain through space and time as controlled by tectonics, sediment supply, climate and locally by autocyclic environmental This study might be beneficial for understanding the controls and stratigraphic evolution of the Red Sea region and will be of great value for reservoir and aquifer characterization, development and management. This modern analog model can also help in providing geological baseline information that would be beneficial for understanding similar ancient fluvial deltaic sediments. The study might provide guides and leads to understand the subsurface facies, stratigraphic architecture and heterogeneity of any potential groundwater aquifers and hydrocarbon reservoirs.

Seismic characterization and origin of clinoforms in lacustrine depositional environments: a case study from the Cretaceous of the South Atlantic

2020 ◽  
pp. SP509-2019-148
Author(s):  
Andrew J. Barnett ◽  
Lucy Fu ◽  
Tolu Rapasi ◽  
Cinzia Scotellaro ◽  
Jaydip Guha ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Lower Energy ◽  
Gamma Ray ◽  
Depositional Environments ◽  
Longshore Sediment Transport ◽  
Seismic Characterization ◽  
Bona Fide ◽  
Flooding Events ◽  
Gamma Ray Log

AbstractThe lacustrine Itapema Formation in the Santos Basin locally comprises 102 m thick clinoforms identified seismically and corroborated by several well penetrations. Individual clinoforms, as proven by well penetrations, are composed of 102 m thick successions of basinward-dipping molluscan grainstones and rudstones. Manual dip picking of borehole images shows upward-increasing dips consistent with seismic geometries and a predominance of longshore sediment transport. Clinoforms are bound at their top and base by strata with significantly lower dips recognizable on both seismic and borehole images. Elevated gamma-ray log responses together with sidewall core samples indicate that these intervals correspond to more argillaceous facies which are interpreted as lake flooding events. While the existence of bona fide clinoforms is demonstrated by a range of subsurface data, their precise origin remains enigmatic. The majority of the bivalve genera that make up the grain-supported carbonates appear to be infaunal or semi-infaunal. As such the clinoforms represent large bars produced through the re-working of bivalves from lower-energy depositional environments by shore-parallel currents.

scholarly journals Correction to: Spatiotemporal variability of vegetation due to drought dynamics (2012–2017): a case study of the Upper Paraíba River basin, Brazil

2020 ◽  
Vol 102 (3) ◽  
pp. 965-965
Author(s):  
Glauciene Justino Ferreira da Silva ◽  
Nádja Melo de Oliveira ◽  
Celso Augusto Guimarães Santos ◽  
Richarde Marques da Silva
Keyword(s):  
River Basin ◽  
Spatiotemporal Variability

scholarly journals Is the Sri Lankan ecotourism industry threatened by climate change? A case study of Rekawa coastal wetland using contingent visitation approach

2019 ◽  
Vol 25 (3) ◽  
pp. 226-243
Author(s):  
Nesha Dushani Salpage ◽  
Margrethe Aanesen ◽  
Oscar Amarasinghe
Keyword(s):  
Climate Change ◽  
At Risk ◽  
Coastal Wetland ◽  
Climatic Factors ◽  
Demographic Characteristics ◽  
Sri Lankan ◽  
Environmental Index ◽  
Adaptation Measures ◽  
The Difference

AbstractThis study investigates intended visitation behavior of tourists toward Rekawa wetland under anticipated climate change (CC) scenarios. An interview-based contingent visitation survey was conducted with 365 foreign and domestic tourists to estimate the effects of CC on future visitation. Based on two IPCC scenarios using two direct and three indirect climatic factors, we composed a CC environmental index. The results show a decline in number of trips equal to 43 per cent and 53 per cent under scenarios 1 and 2 respectively, but the difference is not significant. Foreign and domestic tourists differ significantly with regard to socio-demographic characteristics and beliefs about CC effects at Rekawa. Controlling for such differences, we demonstrate that foreign tourists are less likely than domestic tourists to reduce future visitation to Rekawa due to CC impacts. Still, the future of ecotourism at Rekawa wetland is at risk if adaptation measures are not taken to meet CC impacts.

Sign in / Sign up

Export Citation Format

Share Document