ABSTRACT Tidal amplitude and currents along coastlines will change in conjunction with sea-level ... more ABSTRACT Tidal amplitude and currents along coastlines will change in conjunction with sea-level rise, when certain geomorphic and bathymetric conditions are met. Under conditions of decreasing protection from barrier islands, associated with increased inlet activity or overstepping of islands, tidal amplitude can rapidly increase in estuaries and along mainland coastlines and significantly amplify the effects of a minor sea-level rise. Impacts to coastal systems may be economically and environmentally significant. Additionally, sea-level curves developed from areas where tidal regime change has occurred in the past must be evaluated carefully for the effects of tidal amplitude. The impacts of tidal amplitude changes in response to sea-level rise have been noted in the Minas Basin, Delaware Bay, and, in this study, the Albemarle-Pamlico Estuarine System of North Carolina. Our group is investigating the magnitude of changes in response to variations in geomorphic and bathymetric conditions, and past climate events. Methods include the use of seismic data, sedimentology, microfossil analysis, oxygen isotopes, Mg/Ca, black carbon, and radiocarbon ages to reconstruct paleobathymetry, paleoenvironments and paleoclimate conditions during the late Holocene. Paleobathymetric/paleogeomorphic models are being derived to enable hydrodynamic modeling using Delft3D software. Initial runs for the Pamlico Sound have been performed to reconstruct hydrodynamic conditions during a barrier break-down event associated with the Medieval Climate Anomaly (ca. 1000 cal yr BP). Likewise, models are being used to understand hydrodynamics in the Currituck Sound (a smaller lagoon in northeastern NC) in response to historical inlet activity. Results illustrate the potential for an eight-fold increase in tidal amplitude, with significant variations within the estuarine system, and large increases in tidal currents well into the estuaries, resulting in significant changes to salinity structures and sedimentation patterns.
Barrier islands within sheltered environments are an important natural defense from severe storm ... more Barrier islands within sheltered environments are an important natural defense from severe storm impacts for coastal communities worldwide. Despite their importance, these fetch-limited barrier islands remain understudied and their ability to withstand and recover from storms is not well-understood. Here, we present a case study of Sugarloaf Island in North Carolina that demonstrates the operational use of openly accessible LiDAR and aerial imagery data to quantify synoptic habitat, shoreline, and volumetric change between 2014 and 2020, a period that encompasses four hurricanes and a winter storm event. During this time period, our results show: (1) an 11–13% decrease in marsh and shrub habitat, (2) an average landward shoreline migration of 2.9 m yr−1 and up to 5.2 m yr−1 in extreme areas, and (3) a net volume loss of approximately 9800 m3. The results of this study highlight the importance of storms as a driver of morphologic change on Sugarloaf Island and have implications for b...
Lithofacies analysis is fundamental to unravelling the succession of depositional environments as... more Lithofacies analysis is fundamental to unravelling the succession of depositional environments associated with sea‐level fluctuations. These successions and their timing are often poorly understood. This report defines lithofacies encountered within the north‐eastern North Carolina and south‐eastern Virginia Quaternary section, interprets their depositional environments, presents a model for coastal depositional sequence development in a passive margin setting and uses this understanding to develop the stratigraphy and Quaternary evolutionary history of the region. Data were obtained from numerous drill cores and outcrops. Chronology was based on age estimates acquired using optically stimulated luminescence, amino acid racemization, Uranium series and radiocarbon dating techniques. Geomorphic patterns were identified and interpreted using light detection and ranging imagery. Since lithofacies occurrence, distribution and stratigraphic patterns are different on interfluves than in palaeo‐valleys, this study focused on interfluves to obtain a record of highstand sea‐level cycles with minimal alteration by fluvial processes during subsequent lowstands. Nine primary lithofacies and four diagenetic facies were identified in outcrops and cores. The uppermost depositional sequence on interfluves exhibits an upward succession from shelly marine lithofacies to tidal estuarine lithofacies and is bounded below by a marine ravinement surface and above by the modern land surface. Older depositional sequences in the subsurface are typically bounded above and below by marine ravinement surfaces. Portions of seven depositional sequences were recognized and interpreted to represent deposition from late middle Pleistocene to present. Erosional processes associated with each successive depositional sequence removed portions of older depositional sequences. The stratigraphic record of the most recent sea‐level highstands (Marine Isotope Stage 5a and Marine Isotope Stage 3) is best preserved. Glacio‐isostatic adjustment has influenced depositional patterns so that deposits associated with late Quaternary sea‐level highstands (Marine Isotope Stages 5c, 5a and 3), which did not reach as high as present sea‐level according to equatorial eustatic records, are uplifted and emergent within the study area.
ABSTRACT The mid to late Holocene coastal evolution of the Setiu estuary/lagoon (northeast penins... more ABSTRACT The mid to late Holocene coastal evolution of the Setiu estuary/lagoon (northeast peninsular Malaysia) has been studied using a multidisciplinary/multiproxy approach including sedimentologic, geomorphologic, and ground penetrating radar (GPR) data combined with optically stimulated luminescence (OSL), radiocarbon and Pb-210 age estimates to provide the chronologic framework. The Setiu coastal region of Terengganu comprises five geological and geomorphic units representing distinct evolutionary phases of this coastline. Estimated marine limiting point elevations indicate deposition of an aggradational strandplain shoreline associated with a sea-level elevation of ca. -0.1 to +1.7 m between ca. 6.8 ka and 5.7 ka, in agreement with previous sea-level studies from the Malay-Thai peninsula(Tjia and Fujii, 1992; Tjia, 1997; Kamaludin, 2002; Horton et al. (2005). A rapid sea-level rise may have occurred between ca. 5.7 ka and 3.0 ka resulting in shoreline erosion and a hiatus between successive coastal units. Relative sea-level fall occurred between ca. 3.0 and 1.9 ka, resulting in a progradational system. A brief period of relative sea-level rise or still-stand occurred between ca. 1.9 and 1.4 ka, creating an aggradational to transgressive barrier and estuary. Relative sea-level fall at ca. 1.4 ka caused further progradation and abandonment of the estuary and barrier island. This was followed by another reversal in mode creating another barrier and estuary, bracketed between 1.4 ka and 0.3 ka. The final phase began at ca. 300 cal y BP and established the modern transgressive barrier and Setiu estuary/lagoon, and associated mangrove swamps. The new GPR, OSL and radiocarbon data add to our understanding of Holocene coastal evolution of this coastal system and the response to sea-level change and monsoons and corroborate previous research(Teh, 1980, 1993). Data suggest that sequential development of clinoforms and ultimate progradation is dictated by monsoonal variations, with erosional/depositional cycles occurring on annual to decadal scales. The data support an oscillating relative sea-level possibly governed by meteorological phenomena such as ENSO variability, but a possible correlation to sea-level records from widely separate areas also suggests a global sea-level signal. Thus, coastal facies can be useful proxy indicators for meteorological and paleoclimatic change across a wide temporal spectrum (decadal to millennial time-scales). We performed a high-resolution study of the final phase of coastal evolution and sea-level changes in the Setiu wetland (the past ca. 300 years)based on mangrove swamp foraminifera. Foraminferal data from three surface transects across fringing mangrove swamps were used to interpret foraminiferal data from four cores from high to mid mangrove swamp settings.Patterns of foraminiferal distribution were determined bycorrespondence analysis, canonical correspondence analysis and detrended canonical correspondence analysis of dead assemblage data.We used weighted averaging as the transfer function modeland produced a composite reconstruction of sea level for the last ca. 200 years. Sea level rose during the 19th century at1.26 mm yr-1. Around 1900 CE, roughly coincident with rate increases recorded globally, the rate of sea-level rise increased to 3.2 ±0.6 mm yr-1. This rate is considerably greater than that of global estimates (1.8 to 1.9 ± 0.3 mm yr-1)for the 20th century. These results are in agreement with data from the Gulf of Thailand derived from GPS-corrected tide gauge data and provide additional information to a region withgeographically variable rates of sea-level rise. The data from the Setiu wetland provide the first high-resolution, foraminifera-based sea-level reconstruction from the southeastern South China Sea and expand the utility of foraminifera-based sea-levelstudies to tropical settings.
ABSTRACT Tidal amplitude and currents along coastlines will change in conjunction with sea-level ... more ABSTRACT Tidal amplitude and currents along coastlines will change in conjunction with sea-level rise, when certain geomorphic and bathymetric conditions are met. Under conditions of decreasing protection from barrier islands, associated with increased inlet activity or overstepping of islands, tidal amplitude can rapidly increase in estuaries and along mainland coastlines and significantly amplify the effects of a minor sea-level rise. Impacts to coastal systems may be economically and environmentally significant. Additionally, sea-level curves developed from areas where tidal regime change has occurred in the past must be evaluated carefully for the effects of tidal amplitude. The impacts of tidal amplitude changes in response to sea-level rise have been noted in the Minas Basin, Delaware Bay, and, in this study, the Albemarle-Pamlico Estuarine System of North Carolina. Our group is investigating the magnitude of changes in response to variations in geomorphic and bathymetric conditions, and past climate events. Methods include the use of seismic data, sedimentology, microfossil analysis, oxygen isotopes, Mg/Ca, black carbon, and radiocarbon ages to reconstruct paleobathymetry, paleoenvironments and paleoclimate conditions during the late Holocene. Paleobathymetric/paleogeomorphic models are being derived to enable hydrodynamic modeling using Delft3D software. Initial runs for the Pamlico Sound have been performed to reconstruct hydrodynamic conditions during a barrier break-down event associated with the Medieval Climate Anomaly (ca. 1000 cal yr BP). Likewise, models are being used to understand hydrodynamics in the Currituck Sound (a smaller lagoon in northeastern NC) in response to historical inlet activity. Results illustrate the potential for an eight-fold increase in tidal amplitude, with significant variations within the estuarine system, and large increases in tidal currents well into the estuaries, resulting in significant changes to salinity structures and sedimentation patterns.
Barrier islands within sheltered environments are an important natural defense from severe storm ... more Barrier islands within sheltered environments are an important natural defense from severe storm impacts for coastal communities worldwide. Despite their importance, these fetch-limited barrier islands remain understudied and their ability to withstand and recover from storms is not well-understood. Here, we present a case study of Sugarloaf Island in North Carolina that demonstrates the operational use of openly accessible LiDAR and aerial imagery data to quantify synoptic habitat, shoreline, and volumetric change between 2014 and 2020, a period that encompasses four hurricanes and a winter storm event. During this time period, our results show: (1) an 11–13% decrease in marsh and shrub habitat, (2) an average landward shoreline migration of 2.9 m yr−1 and up to 5.2 m yr−1 in extreme areas, and (3) a net volume loss of approximately 9800 m3. The results of this study highlight the importance of storms as a driver of morphologic change on Sugarloaf Island and have implications for b...
Lithofacies analysis is fundamental to unravelling the succession of depositional environments as... more Lithofacies analysis is fundamental to unravelling the succession of depositional environments associated with sea‐level fluctuations. These successions and their timing are often poorly understood. This report defines lithofacies encountered within the north‐eastern North Carolina and south‐eastern Virginia Quaternary section, interprets their depositional environments, presents a model for coastal depositional sequence development in a passive margin setting and uses this understanding to develop the stratigraphy and Quaternary evolutionary history of the region. Data were obtained from numerous drill cores and outcrops. Chronology was based on age estimates acquired using optically stimulated luminescence, amino acid racemization, Uranium series and radiocarbon dating techniques. Geomorphic patterns were identified and interpreted using light detection and ranging imagery. Since lithofacies occurrence, distribution and stratigraphic patterns are different on interfluves than in palaeo‐valleys, this study focused on interfluves to obtain a record of highstand sea‐level cycles with minimal alteration by fluvial processes during subsequent lowstands. Nine primary lithofacies and four diagenetic facies were identified in outcrops and cores. The uppermost depositional sequence on interfluves exhibits an upward succession from shelly marine lithofacies to tidal estuarine lithofacies and is bounded below by a marine ravinement surface and above by the modern land surface. Older depositional sequences in the subsurface are typically bounded above and below by marine ravinement surfaces. Portions of seven depositional sequences were recognized and interpreted to represent deposition from late middle Pleistocene to present. Erosional processes associated with each successive depositional sequence removed portions of older depositional sequences. The stratigraphic record of the most recent sea‐level highstands (Marine Isotope Stage 5a and Marine Isotope Stage 3) is best preserved. Glacio‐isostatic adjustment has influenced depositional patterns so that deposits associated with late Quaternary sea‐level highstands (Marine Isotope Stages 5c, 5a and 3), which did not reach as high as present sea‐level according to equatorial eustatic records, are uplifted and emergent within the study area.
ABSTRACT The mid to late Holocene coastal evolution of the Setiu estuary/lagoon (northeast penins... more ABSTRACT The mid to late Holocene coastal evolution of the Setiu estuary/lagoon (northeast peninsular Malaysia) has been studied using a multidisciplinary/multiproxy approach including sedimentologic, geomorphologic, and ground penetrating radar (GPR) data combined with optically stimulated luminescence (OSL), radiocarbon and Pb-210 age estimates to provide the chronologic framework. The Setiu coastal region of Terengganu comprises five geological and geomorphic units representing distinct evolutionary phases of this coastline. Estimated marine limiting point elevations indicate deposition of an aggradational strandplain shoreline associated with a sea-level elevation of ca. -0.1 to +1.7 m between ca. 6.8 ka and 5.7 ka, in agreement with previous sea-level studies from the Malay-Thai peninsula(Tjia and Fujii, 1992; Tjia, 1997; Kamaludin, 2002; Horton et al. (2005). A rapid sea-level rise may have occurred between ca. 5.7 ka and 3.0 ka resulting in shoreline erosion and a hiatus between successive coastal units. Relative sea-level fall occurred between ca. 3.0 and 1.9 ka, resulting in a progradational system. A brief period of relative sea-level rise or still-stand occurred between ca. 1.9 and 1.4 ka, creating an aggradational to transgressive barrier and estuary. Relative sea-level fall at ca. 1.4 ka caused further progradation and abandonment of the estuary and barrier island. This was followed by another reversal in mode creating another barrier and estuary, bracketed between 1.4 ka and 0.3 ka. The final phase began at ca. 300 cal y BP and established the modern transgressive barrier and Setiu estuary/lagoon, and associated mangrove swamps. The new GPR, OSL and radiocarbon data add to our understanding of Holocene coastal evolution of this coastal system and the response to sea-level change and monsoons and corroborate previous research(Teh, 1980, 1993). Data suggest that sequential development of clinoforms and ultimate progradation is dictated by monsoonal variations, with erosional/depositional cycles occurring on annual to decadal scales. The data support an oscillating relative sea-level possibly governed by meteorological phenomena such as ENSO variability, but a possible correlation to sea-level records from widely separate areas also suggests a global sea-level signal. Thus, coastal facies can be useful proxy indicators for meteorological and paleoclimatic change across a wide temporal spectrum (decadal to millennial time-scales). We performed a high-resolution study of the final phase of coastal evolution and sea-level changes in the Setiu wetland (the past ca. 300 years)based on mangrove swamp foraminifera. Foraminferal data from three surface transects across fringing mangrove swamps were used to interpret foraminiferal data from four cores from high to mid mangrove swamp settings.Patterns of foraminiferal distribution were determined bycorrespondence analysis, canonical correspondence analysis and detrended canonical correspondence analysis of dead assemblage data.We used weighted averaging as the transfer function modeland produced a composite reconstruction of sea level for the last ca. 200 years. Sea level rose during the 19th century at1.26 mm yr-1. Around 1900 CE, roughly coincident with rate increases recorded globally, the rate of sea-level rise increased to 3.2 ±0.6 mm yr-1. This rate is considerably greater than that of global estimates (1.8 to 1.9 ± 0.3 mm yr-1)for the 20th century. These results are in agreement with data from the Gulf of Thailand derived from GPS-corrected tide gauge data and provide additional information to a region withgeographically variable rates of sea-level rise. The data from the Setiu wetland provide the first high-resolution, foraminifera-based sea-level reconstruction from the southeastern South China Sea and expand the utility of foraminifera-based sea-levelstudies to tropical settings.
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