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Location of Juniperus virginiana (eastern red cedar) stumps and surficial geologic environments of the intertidal zone of Standish Point, Duxbury Bay. Line A-A 0 shows the location of Figure 3.
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The present marine transgression has forced geological and ecological zones vertically higher and landward since the late Pleistocene. A recent investigation in Duxbury Bay, Massachusetts, identified 18 Juniperus virginiana tree stumps emergent on an intertidal flat immediately seaward of a small marsh and pond situated between two eroding drumlins...
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... 3. Stratigraphy of the Duxbury forest site. A simplified cross section A-A 0 (Figure 2) illustrates the stratigraphic relationship of the major stratigraphic units. Dashed lines indicate uncertain boundaries, and dotted lines indicate unconformities. Stratigraphic information was extracted from shallow coring and previous studies ( cf . Hill and FitzGerald, 1992).
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... 2010, 18 tree stumps were discovered in the intertidal zone immediately seaward of the Miles Standish Homestead, Duxbury, Massachusetts. The preserved bark of the stumps was identified as eastern red cedar, Juniperus virginiana , using botanical keys (Bertness, 1999; Petrides, 1998). The position of all stumps was located in three-dimensional space using a combination of high-resolution global positioning system (GPS) equipment and traditional land surveying methodologies. The stumps were located using a Trimble GeoXH handheld GPS system. Each stump was occupied for 2 minutes, and the positions were averaged using the Trimble Pathfinder software package. The horizontal error reported by the Pathfinder software for each location was less than 0.5 m. The vertical errors were in excess of 2 m, and, thus, traditional survey methods were used to locate each stump with respect to mean lower low water (MLLW). A Sokia Autolevel and metric Philadelphia Rod were used to relate the elevation of each stump, the high tide wrack line, and other shoreline features to a locally established bench- mark. The elevations were then referenced to MLLW using the National Oceanic and Atmospheric Administration (NOAA) Duxbury, Massachusetts, tidal station (NOAA, 2010a). The elevation for each stump was recorded at the junction of the highest root with the trunk. Based on observations of living eastern red cedar trees in coastal areas, this is approximately 0.1 m below the ground surface. The survey method is accurate to 0.005 m, and elevations are reported to 0.01 m. Four samples from tree stumps were selected for submis- sion to the National Ocean Science Marine Accelerator Mass Spectrometry (NOSAMS) facility at Woods Hole Oceano- graphic Institute, Woods Hole, Massachusetts. Samples were selected from the highest root and closest to the trunk. A section of the root was removed using a saw close to the trunk and from the root that showed the least amount of alteration and with intact bark. The remaining portion of trunk of the stump was not used, as it was the most degraded. The root material showed a higher degree of preservation and less impact by shipworm borings, algal holdfasts, and abrasion than samples collected from the trunk. Samples were also examined from wood beneath preserved bark, but those samples also showed indications of a high possibility for contamination. Samples were isolated from undisturbed wood as close to the wood-bark interface as possible. Samples were washed in deionized water to remove sediment, dried at 50 8 C for 24 hours, and subsampled before shipping to NOSAMS for analysis. All dates were calibrated using Calib 6.0.1 with the IntCal09 calibration data set (Stuiver and Reimer, 1993). A single Mya arenaria shell was collected from the sediment surface. The shell was articulated and in growth position, with approximately 66% of the shell imbedded in the blue clay layer that underlies the sandy intertidal sediments. The sample was washed with deionized water and sent to NOSAMS for AMS 14 C dating. In total, 28 of shallow sediment cores were acquired with a 5 cm 3 1 m gouge auger. All cores sites were located using the method described above for locating tree stumps. The cores were arranged throughout the site based on a rough grid (Figure 2). Several cores were located in close proximity to tree stumps to capture the stratigraphic sequence and depositional environments adjacent to the trees. Cores were measured and described in the field visually for stratigraphy and sedimen- tology and characterized using a Munsell color chart. Cores were photographed, and reference samples from each stratigraphic unit were extracted and archived at 4 8 C. The rates and elevations measured in this study were compared the sea-level curve of Donnelly (2006) and to tide gauge data to establish a landscape gradient. To accomplish the comparisons, conversion and representation of the data were required. Elevations of stumps were surveyed with respect to MLLW and converted to mean high water (MHW) using the Boston tide gauge data set (NOAA, 2010b). Surveying the high tide line on two different days and comparing the observed elevations to the elevations predicted by tide models verified the conversion. This allowed for determination of the MLLW to MHW offset of 3.05 m. Donnelly (2006) presents a high-resolution sea-level curve for southeastern Massachusetts that spans the last 3000 years. To compare these sea-level points to the stumps surveyed in this study, data points from Donnelly (2006) that were within the temporal range of the dated stumps were extracted and plotted to determine a linear regression sea-level rate based on similar timescales. While Donnelly (2006) presents a rate of 0.80 6 0.25 mm/yr, when the data for the time period of interest are extracted, the rate increases slightly to 1.00 6 0.10 mm/yr. The series of tree stumps studied here was located in the intertidal zone at Standish Point, Duxbury Bay (Figure 2). The stumps were located in three-dimensional space using survey methods (Table 1). The elevation of the stumps ranges between 0.75 and 2.03 m above MLLW. All observed stumps were rooted in either eroding peat deposits or an iron-stained gravelly sand layer just beneath a well-sorted medium sand layer. The root systems of the stumps penetrated into the iron-stained layer. Stumps located where peat was absent had roots elevated above the iron-stained layer, suggesting that the layer was removed. The stumps closer to the modern shoreline were rooted in peat layers, while those more seaward were in the exposed iron-stained layer. Coring of the area hosting the stumps and immediately surrounding the stumps revealed that the iron-stained gravelly sand layer was present beneath the peat in all areas associated with tree stumps (Figure 3). Thickness of peat ranged from absent to 0.95 m over the iron-stained layer, and the overlying sand layer was less than 0.20 m thick. The iron-stained gravelly sand layer ranged in thickness between absent and 0.35 m. Thickest accumulations were observed in the landward-most and central portions of the area hosting stumps. On the eastern and western margins of the area hosting the stumps, the iron-stained, gravelly sand layer was absent, and the surface was characterized by either the well-sorted medium sand sheet or blue clay that relates to lacustrine phases of Cape Cod Bay (Hill and FitzGerald, 1992; Uchupi and Mulligan, 2006). In these areas, the iron-stained layer was absent (Figure 4). Samples were collected from all tree stumps located within the intertidal zone. Four stumps were selected for AMS 14 C dating. The two most landward and two most seaward tree stumps were selected in an attempt to capture the landscape gradient across the field of tree stumps. The age of the stumps formed two clusters, with the seaward stumps clustering together and the landward stumps clustering together (Table 2). The age of the stumps ranged between 2219 6 94 and 2867 6 79 cal YBP. In addition to intertidal tree stumps, the location and elevation of modern beach and shoreface features were also measured and compared to the paleofeatures (Table 3). The modern features included living and dead eastern red cedar trees, elevations of the frontal dune ridge, and the most recent high tide line. These modern environmental indicators serve as a reference point for comparison to similar indicators observed in the geologic record and will assist in reconstructing the timing and style of the transgression. While the tree stumps discovered at Standish Point are not applicable to assist in the development of high-resolution sea- level curves, they can provide some constraint to sea level and information about the evolution of the landscape at the land- water interface and the preflooding terrestrial environment (Barrie and Conway, 2002; Lacourse, Mathewes, and Fedje, 2003). The ages of the stumps span nearly 650 years during a time when sea-level rise rates were significantly lower than present. Current measurements for the City of Boston suggest 2.68 mm/yr over the past 100 years, and Donnelly (2006) reported 1.0 mm/yr for the period between 2000 and 3000 years ago from salt marsh studies. The rate compares well to the 1 mm/yr rate reported for the period around 2500 cal YBP in Cape Cod Bay (Oldale and O’Hara, 1980; Redfield and Rubin, 1962). The rate suggested by the tree stumps is 1.4 mm/yr, with an R 2 of 0.97 (Figure 5). None of the stump positions plots below the Donnelly (2006) sea-level curve, and most plot 0.75 to 1.25 m above the Donnelly (2006) sea-level curve. Eastern red cedars have been observed growing in close proximity to salt marshes and on coastal barrier systems. Data from Waquoit Bay National Estuarine Reserve (C. Maio, 2011, unpublished data; C. Wiedman, 2011, unpublished data) suggest that these trees are capable of living within 0.5 m vertically of mean high water when on exposed barrier systems and lower when in close proximity to sheltered salt marsh and back barrier environments. Three modern cedars were surveyed as well. One was dead, but upright. The other two appeared healthy with no signs of dead growth (Table 3). Tree DS21 was located on the upper portion of the frontal dune ridge. The elevation of the sand against the trunk was 4.73 m with respect to MLLW. The sand was removed to determine the elevation of the intersection of the highest root with the trunk. The elevation of the intersection was 4.33 m with respect to MLLW. A total of 0.40 m of sand had accumulated at the base of the trunk since this tree germinated. Examination of eastern red cedars in areas without high mobile sediments suggests that the intersection of the highest root with the trunk occurs at approximately 0.10 m below ground level. When compared with the intertidal tree stumps, this elevation results in a slightly higher rate of 1.4 mm/yr. If this rate is compared to the Donnelly ...
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... recessional and medial moraines (Hill and FitzGerald, 1992). The marine landscape of Cape Cod Bay hosted a large proglacial lake, Glacial Lake Cape Cod, during the immediate deglacial phases that transitioned into a marine environment during ice retreat and subsequent transgression (Knebel et al ., 1996). The deepest portion of Cape Cod Bay exceeds 58 m and exhibits evidence of scour, suggesting rapid drainage of the lacustrine system through the Race Point Channel, adjacent to the northern tip of Cape Cod. Present-day depths in Duxbury Bay rarely exceed 4 m, and 10 m in deeper subtidal channels (Hill and FitzGerald, 1992; National Ocean Service, 2010). Coastal processes occurring during the past 6000 years resulted in the development of a series of sandy barriers and spits, which have evolved to link the eroding drumlins and protect the bay from wave attack (FitzGerald, Buynevich, and Rosen, 2001; Hill and FitzGerald, 1992). All of the spits and barriers of the complex bay show strong evidence of transgression and varying phases of barrier stability (Hill and FitzGerald, 1992). The stratigraphy of the area immediately adjacent to the present high tide line consists of granitic bedrock overlain by various thicknesses of till and a sequence of glacial lacustrine clays, capped by modern sandy marine and marginal marine salt marsh deposits. During the regression, terrestrial facies, including paleosols and freshwater marshes, were deposited over the clays. As sea level began to rise, the older units were eroded and reworked, and a transgressive sand sheet was deposited (Hill and FitzGerald, 1992). After a series of two large coastal storms impacted the area in March 2010, 18 tree stumps were discovered in the intertidal zone immediately seaward of the Miles Standish Homestead, Duxbury, Massachusetts. The preserved bark of the stumps was identified as eastern red cedar, Juniperus virginiana , using botanical keys (Bertness, 1999; Petrides, 1998). The position of all stumps was located in three-dimensional space using a combination of high-resolution global positioning system (GPS) equipment and traditional land surveying methodologies. The stumps were located using a Trimble GeoXH handheld GPS system. Each stump was occupied for 2 minutes, and the positions were averaged using the Trimble Pathfinder software package. The horizontal error reported by the Pathfinder software for each location was less than 0.5 m. The vertical errors were in excess of 2 m, and, thus, traditional survey methods were used to locate each stump with respect to mean lower low water (MLLW). A Sokia Autolevel and metric Philadelphia Rod were used to relate the elevation of each stump, the high tide wrack line, and other shoreline features to a locally established bench- mark. The elevations were then referenced to MLLW using the National Oceanic and Atmospheric Administration (NOAA) Duxbury, Massachusetts, tidal station (NOAA, 2010a). The elevation for each stump was recorded at the junction of the highest root with the trunk. Based on observations of living eastern red cedar trees in coastal areas, this is approximately 0.1 m below the ground surface. The survey method is accurate to 0.005 m, and elevations are reported to 0.01 m. Four samples from tree stumps were selected for submis- sion to the National Ocean Science Marine Accelerator Mass Spectrometry (NOSAMS) facility at Woods Hole Oceano- graphic Institute, Woods Hole, Massachusetts. Samples were selected from the highest root and closest to the trunk. A section of the root was removed using a saw close to the trunk and from the root that showed the least amount of alteration and with intact bark. The remaining portion of trunk of the stump was not used, as it was the most degraded. The root material showed a higher degree of preservation and less impact by shipworm borings, algal holdfasts, and abrasion than samples collected from the trunk. Samples were also examined from wood beneath preserved bark, but those samples also showed indications of a high possibility for contamination. Samples were isolated from undisturbed wood as close to the wood-bark interface as possible. Samples were washed in deionized water to remove sediment, dried at 50 8 C for 24 hours, and subsampled before shipping to NOSAMS for analysis. All dates were calibrated using Calib 6.0.1 with the IntCal09 calibration data set (Stuiver and Reimer, 1993). A single Mya arenaria shell was collected from the sediment surface. The shell was articulated and in growth position, with approximately 66% of the shell imbedded in the blue clay layer that underlies the sandy intertidal sediments. The sample was washed with deionized water and sent to NOSAMS for AMS 14 C dating. In total, 28 of shallow sediment cores were acquired with a 5 cm 3 1 m gouge auger. All cores sites were located using the method described above for locating tree stumps. The cores were arranged throughout the site based on a rough grid (Figure 2). Several cores were located in close proximity to tree stumps to capture the stratigraphic sequence and depositional environments adjacent to the trees. Cores were measured and described in the field visually for stratigraphy and sedimen- tology and characterized using a Munsell color chart. Cores were photographed, and reference samples from each stratigraphic unit were extracted and archived at 4 8 C. The rates and elevations measured in this study were compared the sea-level curve of Donnelly (2006) and to tide gauge data to establish a landscape gradient. To accomplish the comparisons, conversion and representation of the data were required. Elevations of stumps were surveyed with respect to MLLW and converted to mean high water (MHW) using the Boston tide gauge data set (NOAA, 2010b). Surveying the high tide line on two different days and comparing the observed elevations to the elevations predicted by tide models verified the conversion. This allowed for determination of the MLLW to MHW offset of 3.05 m. Donnelly (2006) presents a high-resolution sea-level curve for southeastern Massachusetts that spans the last 3000 years. To compare these sea-level points to the stumps surveyed in this study, data points from Donnelly (2006) that were within the temporal range of the dated stumps were extracted and plotted to determine a linear regression sea-level rate based on similar timescales. While Donnelly (2006) presents a rate of 0.80 6 0.25 mm/yr, when the data for the time period of interest are extracted, the rate increases slightly to 1.00 6 0.10 mm/yr. The series of tree stumps studied here was located in the intertidal zone at Standish Point, Duxbury Bay (Figure 2). The stumps were located in three-dimensional space using survey methods (Table 1). The elevation of the stumps ranges between 0.75 and 2.03 m above MLLW. All observed stumps were rooted in either eroding peat deposits or an iron-stained gravelly sand layer just beneath a well-sorted medium sand layer. The root systems of the stumps penetrated into the iron-stained layer. Stumps located where peat was absent had roots elevated above the iron-stained layer, suggesting that the layer was removed. The stumps closer to the modern shoreline were rooted in peat layers, while those more seaward were in the exposed iron-stained layer. Coring of the area hosting the stumps and immediately surrounding the stumps revealed that the iron-stained gravelly sand layer was present beneath the peat in all areas associated with tree stumps (Figure 3). Thickness of peat ranged from absent to 0.95 m over the iron-stained layer, and the overlying sand layer was less than 0.20 m thick. The iron-stained gravelly sand layer ranged in thickness between absent and 0.35 m. Thickest accumulations were observed in the landward-most and central portions of the area hosting stumps. On the eastern and western margins of the area hosting the stumps, the iron-stained, gravelly sand layer was absent, and the surface was characterized by either the well-sorted medium sand sheet or blue clay that relates to lacustrine phases of Cape Cod Bay (Hill and FitzGerald, 1992; Uchupi and Mulligan, 2006). In these areas, the iron-stained layer was absent (Figure 4). Samples were collected from all tree stumps located within the intertidal zone. Four stumps were selected for AMS 14 C dating. The two most landward and two most seaward tree stumps were selected in an attempt to capture the landscape gradient across the field of tree stumps. The age of the stumps formed two clusters, with the seaward stumps clustering together and the landward stumps clustering together (Table 2). The age of the stumps ranged between 2219 6 94 and 2867 6 79 cal YBP. In addition to intertidal tree stumps, the location and elevation of modern beach and shoreface features were also measured and compared to the paleofeatures (Table 3). The modern features included living and dead eastern red cedar trees, elevations of the frontal dune ridge, and the most recent high tide line. These modern environmental indicators serve as a reference point for comparison to similar indicators observed in the geologic record and will assist in reconstructing the timing and style of the transgression. While the tree stumps discovered at Standish Point are not applicable to assist in the development of high-resolution sea- level curves, they can provide some constraint to sea level and information about the evolution of the landscape at the land- water interface and the preflooding terrestrial environment (Barrie and Conway, 2002; Lacourse, Mathewes, and Fedje, 2003). The ages of the stumps span nearly 650 years during a time when sea-level rise rates were significantly lower than present. Current measurements for the City of Boston suggest 2.68 mm/yr over the past 100 years, and Donnelly (2006) reported 1.0 mm/yr for the period between 2000 and 3000 years ago from salt marsh studies. The rate compares well to the 1 ...
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... recent high tide line. These modern environmental indicators serve as a reference point for comparison to similar indicators observed in the geologic record and will assist in reconstructing the timing and style of the transgression. While the tree stumps discovered at Standish Point are not applicable to assist in the development of high-resolution sea- level curves, they can provide some constraint to sea level and information about the evolution of the landscape at the land- water interface and the preflooding terrestrial environment (Barrie and Conway, 2002; Lacourse, Mathewes, and Fedje, 2003). The ages of the stumps span nearly 650 years during a time when sea-level rise rates were significantly lower than present. Current measurements for the City of Boston suggest 2.68 mm/yr over the past 100 years, and Donnelly (2006) reported 1.0 mm/yr for the period between 2000 and 3000 years ago from salt marsh studies. The rate compares well to the 1 mm/yr rate reported for the period around 2500 cal YBP in Cape Cod Bay (Oldale and O’Hara, 1980; Redfield and Rubin, 1962). The rate suggested by the tree stumps is 1.4 mm/yr, with an R 2 of 0.97 (Figure 5). None of the stump positions plots below the Donnelly (2006) sea-level curve, and most plot 0.75 to 1.25 m above the Donnelly (2006) sea-level curve. Eastern red cedars have been observed growing in close proximity to salt marshes and on coastal barrier systems. Data from Waquoit Bay National Estuarine Reserve (C. Maio, 2011, unpublished data; C. Wiedman, 2011, unpublished data) suggest that these trees are capable of living within 0.5 m vertically of mean high water when on exposed barrier systems and lower when in close proximity to sheltered salt marsh and back barrier environments. Three modern cedars were surveyed as well. One was dead, but upright. The other two appeared healthy with no signs of dead growth (Table 3). Tree DS21 was located on the upper portion of the frontal dune ridge. The elevation of the sand against the trunk was 4.73 m with respect to MLLW. The sand was removed to determine the elevation of the intersection of the highest root with the trunk. The elevation of the intersection was 4.33 m with respect to MLLW. A total of 0.40 m of sand had accumulated at the base of the trunk since this tree germinated. Examination of eastern red cedars in areas without high mobile sediments suggests that the intersection of the highest root with the trunk occurs at approximately 0.10 m below ground level. When compared with the intertidal tree stumps, this elevation results in a slightly higher rate of 1.4 mm/yr. If this rate is compared to the Donnelly (2006) sea-level curve, it shows a clear change, deceleration, in the rate of sea-level rise at 1000 cal YBP. The slowing of sea-level rise and increasing landscape gradient suggest that the sea-level curve does not represent the actual rate of landscape migration. A series of elevations would be required between 2200 cal YBP and the present to better constrain the landscape migration rate and the relationship to the sea-level rise rate. The distance between tree DS21 and stump DS18 is 179 m. If an assumption is made that the surface on which DS21 is presently growing is a time-transgressive surface and is directly correlative to the surface on which DS18 was growing when alive, then a gradient can be calculated that represents the slope of the landscape during the transgression. The vertical distance between DS21 and DS18 is 3.49 m. The landscape gradient was calculated as 0.020. However, the preserved stumps of the sunken forest occur in a linear zone that is 141 m in length, measured perpendicularly from the present high tide line. The distance from DS21 to the shore- parallel position of the most landward stump, DS06, is 38 m. There are no data points between DS21 and DS06. The landscape gradient for the sunken forest is 0.006 m, while the landscape gradient between the modern trees and the landward-most stump is 0.077 m (Figure 6). The change in gradient suggests either a change in the rate of sea-level rise, which is also seen in sea-level curves for the area and the northeastern United States coastal system (Barnhardt, Belknap, and Kelley, 1997; Church and White, 2006; Donnelly, 2006; Gehrels, 1999; Gehrels, Belknap, and Kelley, 1996; Gehrels et al ., 2005; Oldale and O’Hara, 1980; Redfield and Rubin, 1962) or influence of the preexisting topography. Elevation surveys with DS21 and the low-lying Allen Pond, as well as the drumlin-trough-drumlin morphology, do not support a strong preexisting topography. The lack of the iron-stained layer and preserved peat below the modern estuarine/beach sands east and west of the area with tree stumps suggests the transgression removed the original terrestrial landscape. In these locations, the ravine- ment unconformity is either just below or at the present surface. The paleo-environmental conditions were reconstructed by interpreting the surficial geology (Figure 2), the core stratigraphy (Figure 3), and the iron-stained layer thickness (Figure 4). The reconstruction suggests that the eroding drumlins extended further seaward from their present location, and the low area between drumlins was low enough to develop a paleosol, the iron-stained layer, and peat deposits, which survived transgressive reworking. Large areas of the paleolandscape were removed from the geologic record by erosion and reworking of sediment during the transgression. The locations of these areas are highlighted by the lack of the iron-stained layer and/or peat, the presence of blue clay at the surface, and/or a thin drape of modern sands over blue clay or till. The stumps discovered at Standish Point, Duxbury, record a component of the evolution of the Duxbury Bay system. The presence of the 18 stumps and the associated preserved landscape features strongly suggest that the existing topography extended seaward much further than today. The eroding drumlins to the east and west created a small topographic depression that allowed for the development of a lowland coastal forest that was preserved during the transgression by creation of a salt marsh in the low areas as sea level rose. The morphology of the paleosystem and relationship of features and depositional environments are strongly represented by the present system as a retreating sandy beach links to two drumlins and is migrating landward into a low area that hosts eastern red cedar trees, freshwater marsh areas, and a small pond. The presence of the stumps allows for the development of a rate of landscape transgression. While similar to a sea-level rise curve, the landscape transgression curve relates the conversion of one depositional environment to another. In this case, eastern red cedar–dominated coastal forest to exposed beach face and/or salt marsh. The vertical rate of landscape transgression is estimated as 1.4 mm/yr, i.e . slightly higher than the 1.0 mm/yr local sea-level rise extracted from Donnelly (2006) for the same time period. The preservation of the iron- stained layer and tree stumps further suggests a low-energy environment with a passive style of flooding, unlike the exposed areas of Duxbury Beach, as reported by FitzGerald, Buynevich, and Rosen (2001). Further, it suggests that a barrier system may have been in place by ~ 2900 cal YBP, as suggested by Hill and FitzGerald (1992). The Duxbury sunken forest represents a window into the evolution of the region’s coastline. The preserved paleogeo- graphic and paleo-environmental information highlights the style of flooding during the transgression, as well as the change in landscape gradients in response to flooding of Duxbury Bay and higher-energy wave attack due to deeper water throughout the bay. The information contained within sites such as the Duxbury sunken forest can provide detailed contexts for the precolonial coastal system and constrain models of evolution and impacts of natural processes for both hindcasting and forecasting. The insight from the site has the potential to elucidate the precolonial Native American uses of the landscape through reconstruction of the geogra- phy and locating preserved submerged cultural heritage sites. We would like to thank the University of Massachusetts– Boston for providing financial support for the project through a Joseph P. Healey Research Grant (Gontz), the homeowners on Standish Point for allowing access to the site, and University of Massachusetts–Boston undergraduate students Ekatherina Wagenknecht and David Gosselin for providing assistance during survey work. The National Ocean Sciences Accelerator Mass Spectrometry Facility (NOSAMS) conduct- ed the 14 C AMS dating, and we would like to thank them for their rapid analysis of the samples. We would like to thank Dr. Chris Weidman of the Massachusetts Department of Conservation and Recreation and the Waquoit Bay National Estuarine Reserve for his comments and providing access to unpublished ...
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... Initial bathymetry influences the overall sediment availability, while tidal range affects the bed-level change by determining the amount of sediment that can be redistributed (van Maanen et al., 2013a). The average bathymetry in Massachusetts Bay is about 6 m (Signell and Butman, 1992), which is larger than 2 m in Plymouth Bay (Gontz et al., 2013). This shows that different amounts of sediment can be redistributed in the basins, which is one of the possible reasons accounting for the differences in morphology. ...
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... But ubiquitous erosion and decomposition processes during the Quaternary reduce the chances of discovering trees in their original locations. The rare localities that do offer such records are connected to potentially fast depositing environments, such as river flood-plains, alluvial fans, tephra deposits, bogs or dunes ( Pilcher et al. 1995;Pregitzer et al. 2000;Noshiro et al. 2002;Edvardsson et al. 2016;Murton et al. 2017), as well as to former land surfaces in shallow waters that were rapidly submerged following both marine and lacustrine water level increases (Langridge et al. 2012;Gontz et al. 2013). ...
For the first time, evidence of a submerged pine forest from the early Holocene can be documented in a central European lake. Subaquatic tree stumps were discovered in Lake Giesenschlagsee at a depth of between 2 and 5 m using scuba divers, side‐scan sonar and a remotely operated vehicle. Several erect stumps, anchored to the ground by roots, represent an in situ record of this former forest. Botanical determination revealed the stumps to be Scots pine (Pinus sylvestris) with an individual tree age of about 80 years. The trees could not be dated by means of dendrochronology, as they are older than the regional reference chronology for pine. Radiocarbon ages from the wood range from 10 880±210 to 10 370±130 cal. a BP, which is equivalent to the mid‐Preboreal to early Boreal biozones. The trees are rooted in sedge peat, which can be dated to this period as well, using pollen stratigraphical analysis. Tilting of the peat bed by 4 m indicates subsidence of the ground due to local dead ice melting, causing the trees to become submerged and preserved for millennia. Together with recently detected Lateglacial in situ tree occurrences in nearby lakes, the submerged pine forest at Giesenschlagsee represents a new and highly promising type of geo‐bio‐archive for the wider region. Comparable in situ pine remnants occur at some terrestrial (buried setting) and marine (submerged setting) sites in northern central Europe and beyond, but they partly differ in age. In general, the in situ pine finds document shifts of the zonal boreal forest ecosystem during the late Quaternary.
... Since 1920, there has been a threefold increase in the rate of SLR, when compared with the previous millennium from 1 mm/yr to 3 mm/yr, resulting in widespread landward migration of coastal Table 3 Radiocarbon dates obtained from aging carbonate shell samples using continuous flow atomic mass spectrometry (CFAMS). All ages were calibrated using Calib version 7.0.1 with the Marine13 calibration data set (Reimer et al., 2013) applying a marine reservoir correction (ΔR) of ΔR = −95 ±45 14 C years (Stuiver and Braziunas, 1993;Little, 1999 landscapes (Donnelly, 2005;Kemp et al., 2009;Maio et al., 2012;Gontz et al., 2013). Within Unit B, between 5.9 m (WAQ1) and 6.2 m (WAQ2 and WAQ3), there is an unprecedented increase in grain size. ...
The impact of storm events on the sediment dynamics of the shallow groundwater fed estuaries of Cape Cod, Massachusetts, USA is little understood. To address this, the objectives of this study are to assess sediment dynamics during storm passage and determine whether shallow back-barrier lagoons like Waquoit Bay have the preservation potential for a sedimentary archive of hurricanes. When setting out in this study, it was unclear whether paleotempestological methods could be applied successfully to cores collected from the landward reaches of shallow estuaries of southern New England. Water level and bottom current data using Arm-and-Float tide gauges and SeaHorse Tilt Current Meters was collected during Tropical Storm Irene (2011) were coupled with storm surge modeling projections to better elucidate storm-induced sediment transport mechanisms. Three sediment cores were collected at the head of Waquoit Bay, located 2.8 km from the barrier beach. Grain size analysis of sediment cores was conducted with a laser particle size analyzer at 1 cm increments in order to identify coarse grain anomalies, which can act as a storm event proxy. Bayesian statistics were applied to develop age models of two of the cores based on three Pb pollution chronomarkers and 21 continuous flow 14C AMS ages. The results yield variable sediment accumulation rates between 2 mm/yr to 10 mm/yr, with significantly higher rates occurring in the upper 1 m of sediments. Grain size results are highly variable, and contain numerous large amplitude, short duration fluctuations suggesting that during storm passage coarse sand is deposited in the coring site. The sensitivity of the site to both tropical and extratropical storm events, uncertainties in the age model, and the multiple sediment sources and transport pathways limits the utility of using the Waquoit sediments to determine long-term hurricane frequencies. Results nonetheless provide insights into how extreme storm events impact coastal lagoons.
... The progression of units from the present coast towards the southeast exhibits a pattern that is indicative of a regressive coastal plain (Gontz et al., 2014). Moving further away from the coast to the southeast, the sequence transitions from one that is beach ridge deposition over a transgressive unconformity (Gontz et al., 2013) with a lower beach ridge system beneath the unconformity to a less-clear dune sequence over coffee rock with indications of a beach ridge system below the coffee rock ( Figure 4). The patterns observed in UNIT3 and to some degree in UNIT5 exhibit similarities to other beach systems worldwide that have been correlated to periods of storm erosion and beach recovery (Dougherty, 2013). ...
The world’s large sand islands and mainland sand masses dominate the coastal system of southeastern Queensland with dunes exceeding 240 m in height. Previous work using sediment cores and TL/OSL dating has estimated the age of the dunes at 730,000 years. The system, which is the world’s largest downdrift sand system, has Fraser Island and the Coolala Sand Mass as the two northern-most members. Combined, these form the Fraser Island UNESCO World Heritage Site and the Great Sandy National Park.
Between 2012 and 2015, a series of high-resolution, reconnaissance-level ground penetrating radar lines were acquired on Fraser Island and on the northern end of the Coolala Sand Mass. In total, over 50 km of radar lines were acquired. The lines provide insight into sea-level fluctuations that drive large-scale coastal evolution and reveal the presence of past shoreline complexes that are proposed to be associate with the mid Holocene highstand and the previous interglacial.
The generalized sequence is interpreted as a variable thickness of aeolian sand over beach deposits with a transgressive unconformity at the base of the beach deposits, which is interpreted as the Mid Holocene-to-present system. The Mid Holocene system overlies an older system that has variable preservation and is composed of beach deposits with a transgressive unconformity at the base. In places, portions of the sequence are lightly consolidated with organic material and locally known as “coffee rock”, which is a barrier to coring.
The coastal sequences hold the potential to host an archive of storm, sea level and sediment supply records over at least two interglacial periods. Interpretation and correlation with regional and global climate records will provide insight into the mechanics and dynamics of the climate and environment process-response system.
... The progression of units from the present coast towards the southeast exhibits a pattern that is indicative of a regressive coastal plain (Gontz et al., 2014). Moving further away from the coast to the southeast, the sequence transitions from one that is beach ridge deposition over a transgressive unconformity (Gontz et al., 2013) with a lower beach ridge system beneath the unconformity to a less-clear dune sequence over coffee rock with indications of a beach ridge system below the coffee rock ( Figure 4). The patterns observed in UNIT3 and to some degree in UNIT5 exhibit similarities to other beach systems worldwide that have been correlated to periods of storm erosion and beach recovery (Dougherty, 2013). ...
Gontz, A.M; McCallum, A.B., Moss, P.T., and Shulmeister, J., 2016. Ground penetrating radar observations of present and former coastal environments, Great Sandy National Park, Queensland, Australia. In: Vila-Concejo, A.; Bruce, E.; Kennedy, D.M., and McCarroll, R.J. (eds.), Proceedings of the 14th International Coastal Symposium (Sydney, Australia). Journal of Coastal Research, Special Issue, No. 75, pp. 730734. Coconut Creek (Florida), ISSN 0749-0208. The world's large sand islands and mainland sand masses dominate the coastal system of southeastern Queensland with dunes exceeding 240 m in height. Previous work using sediment cores and TL/OSL dating has estimated the age of the dunes at 730,000 years. This system, the world's largest downdrift sand system, has Fraser Island and the Coolala Sand Mass as the two northern-most members. Combined, these form the Fraser Island UNESCO World Heritage Site and the Great Sandy National Park. Between 2012 and 2015, a series of high-resolution, reconnaissance-level GPR lines were acquired on Fraser Island and on the northern end of the Coolala Sand Mass; totalling over 75 km. The lines provide insight into sea-level fluctuations that drive large-scale coastal evolution and reveal the presence of past shoreline complexes that are proposed to be associated with the mid Holocene highstand and the previous interglacial. The generalized sequence is interpreted as a variable thickness of aeolian sand over beach deposits with a transgressive unconformity at the base of the beach deposits, which is interpreted as the Mid Holocene-to-present system. The Mid Holocene system overlies an older system that has variable preservation and is composed of beach deposits with a transgressive unconformity at the base. In places, portions of the sequence are lightly consolidated with organic material, locally known as coffee rock. The coastal sequences hold the potential to host an archive of storm, sea level and sediment supply records over at least two interglacial periods.
... Along the coast of Plymouth, Massachusetts, Gontz et al. (2013) documented the presence of 18 preserved J. virginiana stumps along the mudflats and fringing saltmarsh of Duxbury Bay. In that study, AMS radiocarbon dating revealed that the trees had been submerged between 2219 ± 94 and 2867 ± 79 calibrated years before present (cal BP), with the topographically highest sample returning the youngest date. ...
... Based on radiocarbon age and subfossil elevation, an approximate rate of landscape transgression for the site was calculated at 1.4 mm/yr with an R 2 value of 0.97. (Gontz et al., 2013). ...
The unique combination of landscapes and processes that are present and operate on Fraser Island (K'gari) create a dynamic setting that is capable of recording past environmental events, climate variations and former landscapes. Likewise, its geographic position makes Fraser Island sensitive to those events and processes. Based on optically stimulated luminescence dating, the records archived within the world's largest sand island span a period that has the potential to exceed 750 ka and contain specific records that are of extremely high resolution over the past 40,000 years. This is due to the geographic position of Fraser Island, which lies in the coastal subtropical region of Queensland Australia. Fraser Island is exposed to the open ocean currents of the Coral Sea on the east coast and the waters of Hervey Bay on its western margin and is positioned to receive moisture from the Indo-Australian monsoon, southeast trade winds and experiences occasional tropical and ex-tropical cyclones. We review literature that presents the current level of understanding of sea level change, ecological variation and environmental change on Fraser Island. The previous works illustrate the importance of Fraser Island and may link processes, environments and climates on Fraser Island with global records.
