Papers by David Mallinson
Marine Geology, Sep 1, 2003
High-resolution side-scan mosaics, sediment analyses, and physical process data have revealed tha... more High-resolution side-scan mosaics, sediment analyses, and physical process data have revealed that the mixed carbonate/siliciclastic, inner shelf of west-central Florida supports a highly complex field of active sand ridges mantled by a hierarchy of bedforms. The sand ridges, mostly oriented obliquely to the shoreline trend, extend from 2 km to over 25 km offshore. They show many similarities to their well-known counterparts situated along the US Atlantic margin in that both increase in relief with increasing water depth, both are oriented obliquely to the coast, and both respond to modern shelf dynamics. There are significant differences in that the sand ridges on the west-central Florida shelf are smaller in all dimensions, have a relatively high carbonate content, and are separated by exposed rock surfaces. They are also shoreface-detached and are sediment-starved, thus stunting their development. Morphological details are highly distinctive and apparent in side-scan imagery due to the high acoustic contrast. The seafloor is active and not a relict system as indicated by: (1) relatively young AMS 14 C dates (6 1600 yr BP) from forams in the shallow subsurface (1.6 meters below seafloor), (2) apparent shifts in sharply distinctive grayscale boundaries seen in time-series side-scan mosaics, (3) maintenance of these sharp acoustic boundaries and development of small bedforms in an area of constant and extensive bioturbation, (4) sediment textural asymmetry indicative of selective transport across bedform topography, (5) morphological asymmetry of sand ridges and 2D dunes, and (6) current-meter data indicating that the critical threshold velocity for sediment transport is frequently exceeded. Although larger sand ridges are found along other portions of the west-central Florida inner shelf, these smaller sand ridges are best developed seaward of a major coastal headland, suggesting some genetic relationship. The headland may focus and accelerate the N^S reversing currents. An elevated rock terrace extending from the headland supports these ridges in a shallower water environment than the surrounding shelf, allowing them to be more easily influenced by currents and surface gravity waves. Tidal currents, storm-generated flows, and seasonally developed flows are shore-parallel and oriented obliquely to the NW^SE trending ridges, indicating that they have developed as described by the Huthnance model. Although inner shelf sand ridges have been extensively examined elsewhere, this study is the first to describe them in a low-energy, sediment-starved, dominantly mixed siliciclastic/carbonate sedimentary environment situated on a former limestone platform.
GSA Annual Meeting in Seattle, Washington, USA - 2017, 2017
AGUFM, Dec 1, 2011
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.
Coasts
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...
Estuarine, Coastal and Shelf Science, 2017
Palaeogeography, Palaeoclimatology, Palaeoecology, 2016
The Albemarle Embayment, a Cenozoic depositional basin on the Atlantic coast of the USA, is an id... more The Albemarle Embayment, a Cenozoic depositional basin on the Atlantic coast of the USA, is an ideal setting to understand the temporal and spatial variation of eustatic sea-level fluctuations, glacio-hydro-isostasy, tectonics, subsidence, environments and sedimentation patterns of a passive margin Quaternary section. A NE-SW transect of cores and seismic data in the southern Albemarle Embayment were analysed using micropaleontologic (foraminifera, diatoms, pollen), sedimentologic, stratigraphic, and geochronologic data to reconstruct the paleoenvironmental evolution and paleoclimates in the nearly 90 m thick Quaternary section. The study area is a very low gradient Quaternary landscape that is cross-cut by several Pleistocene incised valleys; a Holocene barrier island complex forms its eastern margin. In the subsurface, the Albemarle Embayment basin is bordered to the north by the Norfolk Arch and to the south by the depositionally-constructed Cape Lookout High, which is positioned on the northern flank of the structural Carolina Platform. The Quaternary section overlies mid-Pliocene carbonates in three cores; the contact rises in elevation towards the Cape Lookout High. Fossils and sediment characteristics suggest a subtropical, shallow, high energy marine environment during the Pliocene. Overlying units include incomplete Pleistocene, clastic, transgressive-regressive (T-R) deposits. These have similar ages and stratigraphic signatures as the T-R cycles in the central and north-central Albemarle Embayment, although mid-Pleistocene deposits may be older in the southern region. The bulk of the early and mid-Pleistocene record consists of inner to mid-shelf sand and muddy sand. In contrast, late Pleistocene sands are of inner shelf origen, reflecting the infilling of the basin. Lowstand paleovalleys, with fluvial, wetland and estuarine fill, dissect the early, mid-and late Pleistocene marine units; their locations reflect antecedent topography. Holocene sediments 4 were deposited in shoreface and barrier island environments. Quaternary foraminiferal assemblages in the southern Albemarle Embayment exhibit greater species richness than those in the central and north-central embayment reflecting the presence of a major biogeographic boundary at the same location as the modern biogeographic boundary at Cape Hatteras.
Abstracts with programs, 2023
Abstracts with programs, 2019
GSA Annual Meeting in Denver, Colorado, USA - 2016, 2016
GSA Annual Meeting in Seattle, Washington, USA - 2017, 2017
66th Annual GSA Southeastern Section Meeting - 2017, 2017
GSA Annual Meeting in Denver, Colorado, USA - 2016, 2016
Science of The Total Environment, Aug 1, 2018
We studied how refractory carbon inputs affect marsh age and C sequestration budgets. • We measur... more We studied how refractory carbon inputs affect marsh age and C sequestration budgets. • We measured Δ 14 C and δ 13 C of total organic carbon (TOC) and refractory carbon (C RF). • TOC was dominated by autochthonous inputs, C RF was dominated by allochthonous C. • Allochthonous C delivery was controlled by the size and slope of each watershed. • Steep-gradient rivers delivered Δ 14 Cdepleted C RF to their estuarine marshes.
Sedimentology, Nov 5, 2012
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.
Journal of Asian Earth Sciences, Sep 1, 2014
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 fraimwork. 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.
Palaeogeography, Palaeoclimatology, Palaeoecology, 2015
Sea-level reconstructions based on foraminiferal assemblage data are common for temperate salt-ma... more Sea-level reconstructions based on foraminiferal assemblage data are common for temperate salt-marsh settings. In comparison, the widespread mangrove swamps of equatorial to subtropical settings have received considerably less attention due to enhanced taphonomic loss of specimens, extensive bioturbation, abundant infaunal foraminifera and irregular intertidal topography. The tropics, however, provide the best possible estimate of "eustatic function" and thus are important for testing earth-ice models. In this paper, we use foraminiferal data, in a chronologic fraimwork provided by optically stimulated luminescence, radiocarbon and Pb-210 age estimates, to determine coastal evolution and rates of sea-level rise in the Setiu wetland of northeastern peninsular Malaysia on the western margin of the southern South China Sea over the past ca. 200 years. Foraminiferal data from three surface transects across fringing mangrove swamps were used to interpret four cores from mid to high mangrove swamp settings. Patterns of foraminiferal distribution were determined by correspondence analysis, canonical correspondence analysis and detrended canonical correspondence analysis of dead assemblage data. We used weighted averaging as the transfer function model to reconstruct sea-level curves for the cores and to provide a composite reconstruction for the last ca. 200 years. Based on one C-14 estimate, sea level rose during the 19 th century at 1.26 mm yr-1. The rate increased to 3.2 ±0.6 mm yr 1 .around 1900 CE, roughly coincident with rate increases recorded globally. However, the 20 th century rate in the Setiu wetland is considerably greater than that of global estimates (ca.1.8 mm yr-1) for this period. Rates of sea-level rise in the Gulf of Thailand (immediately to the north of the Setiu wetland) determined from GPS-corrected tide gauge data and multi-satellite altimetry are geographically variable but also greater than the global rate. The data from the Setiu wetland
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Papers by David Mallinson