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  • 1
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    Fluvial suspended sediment transfer and lacustrine sedimentation of recent flood turbidites in proglacial Eklutna Lake, western Chugach Mountains, Alaska
    Wiley ; 2021
    In:  Hydrological Processes Vol. 35, No. 10 ( 2021-10)
    Details
    In: Hydrological Processes, Wiley, Vol. 35, No. 10 ( 2021-10)
    Abstract: Suspended sediment delivery and deposition in proglacial lakes is generally sensitive to a wide range of hydrometeorologic and geomorphic controls. High discharge conditions are of particular importance in many glaciolacustrine records, with individual floods potentially recorded as distinctive turbidites. We used an extensive network of surface sediment cores and hydroclimatic monitoring data to analyse recent flood turbidites and associated sediment transfer controls over instrumental periods at Eklutna Lake, western Chugach Mountains, Alaska. Close to a decade of fluvial data from primary catchment tributaries show a dominating influence of discharge on sediment delivery, with various interconnections with other related hydroclimatic controls. Multivariate fluvial models highlight and help quantify some complexities in sediment transfer, including intra‐annual variations, meteorological controls, and the influence of subcatchment glacierization. Sediments deposited in Eklutna Lake during the last half century are discontinuously varved and contain multiple distinctive turbidites. Over a 30‐year period of stratigraphic calibration, we correlate the four thickest flood turbidites (1989, 1995, 2006, and 2012) to specific regional storms. The studied turbidites correlate with late‐summer and early‐autumn rainstorms with a magnitude of relatively instantaneous sedimentation 3–15 times greater than annual background accumulation. Our network of sediment core data captured the broad extent and sediment variability among the study turbidites and background sediment yield. Within‐lake spatial modelling of deposition quantifies variable rates of downlake thinning and sediment focusing effects, and highlights especially large differences between the thickest flood turbidites and background sedimentation. This we primarily relate to strongly contrasting dispersion processes controlled by inflow current strength and turbidity. Sediment delivery is of interest for this catchment because of reservoir and water supply operations. Furthermore, although smaller floods may not be consistently represented, the lake likely contains a valuable proxy record of regional flooding proximal to major population centers of south‐central Alaska including Anchorage.
    Type of Medium: Online Resource
    ISSN: 0885-6087 , 1099-1085
    URL: Issue
    URL: Article
    DOI: 10.1002/hyp.v35.10
    DOI: 10.1002/hyp.14375
    Language: English
    Publisher: Wiley
    Publication Date: 2021
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  • 2
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    Suspended sediment deposition and sediment yields at Lake Peters, northeast Brooks Range, Alaska: Fluvial‐ and lake‐based approaches
    Wiley ; 2023
    In:  Earth Surface Processes and Landforms
    Details
    In: Earth Surface Processes and Landforms, Wiley
    Abstract: Lake‐based studies can provide seasonal‐ to millennial‐scale records of sediment yield to improve our understanding of catchment‐scale sediment transfer and complement shorter fluvial‐based sediment transport studies. In this study, sediment accumulation rates at 40 coring locations in Lake Peters, Brooks Range, Alaska, over ca. 42 years, calculated using fallout radionuclides and sediment density patterns, were spatially modelled based on distance from the primary inflow and lake water depth. We estimated mean interdecadal specific sediment yield (Mg km −2  year −1 ) using the spatially modelled sediment accumulation rates and compared that result to fluvial‐based sediment delivery for 2015–2016 open‐channel seasons, as well as to yields reported for other Arctic catchments. Using the lake‐based method, mean yield to Lake Peters between ca. 1973 and 2015 was 52 ± 12 Mg km −2  year −1 , which is comparable with fluvial‐based modelling results of 33 (20–60) Mg km −2  year −1 in 2015 and 79 (50–140) Mg km −2  year −1 in 2016 (95% confidence intervals), respectively. Although 2016 was a year of above average sedimentation, the last extreme depositional event probably occurred between ca. 1970 and 1976 when a basal layer of fine sand was deposited in a broadly distributed, relatively thick and coarse bed, which we used for lake‐wide correlation. The dual lacustrine–fluvial method approach permits study of within‐lake and catchment‐scale processes. Within Lake Peters, sedimentation patterns show decreasing fluxes down‐lake, sediment bypassing near the primary inflow, the influence of secondary inflows and littoral redistribution, and a focusing effect in the deep proximal basin. At the watershed scale, sediment yield is largely driven by intense summer rainfall and strong seasonal hydroclimatic variability. This research informs paleo‐environmental reconstruction and environmental system modelling in Arctic lake catchments.
    Type of Medium: Online Resource
    ISSN: 0197-9337 , 1096-9837
    URL: Article
    DOI: 10.1002/esp.5642
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 1479188-2
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  • 3
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    Late Pleistocene mountain glaciation in Alaska: key chronologies
    Wiley ; 2008
    In:  Journal of Quaternary Science Vol. 23, No. 6-7 ( 2008-09), p. 659-670
    Details
    In: Journal of Quaternary Science, Wiley, Vol. 23, No. 6-7 ( 2008-09), p. 659-670
    Abstract: Moraine sequences of mountain glaciers can be used to infer spatial and temporal patterns of climate change across the globe. Alaska is an accessible high‐latitude location in the Northern Hemisphere and contains a rich record of alpine glaciation. Here, we highlight the key chronologies from three mountain ranges in Alaska that reveal the timing and spatial extent of Late Pleistocene glaciation, and pay particular attention to age of the penultimate glaciation. The most extensive glacier advance of the last glaciation occurred prior to the last global glacial maximum. Cosmogenic exposure ages from moraine boulders in three sites spanning 800 km indicate that this penultimate advance most likely culminated during marine isotope stage (MIS) 4 or early MIS 3. During MIS 2, more limited glacier expansion generated multiple moraines that span from prior to the global Last Glacial Maximum (LGM) through the Lateglacial period. Glaciers retreated from their terminal positions ca. 27–25 ka in arctic Alaska and ca. 22–19 ka in southern Alaska. Moraines in at least two ranges date to 12–11 ka, indicating a glacial advance during the Younger Dryas period. Reconstructed equilibrium‐line altitudes of both penultimate and MIS 2 glaciers were lowered only 300–600 m – much less than elsewhere in the Americas. Alaska is documented to have been more arid during MIS 2, perhaps due in large part to the exposure of the Bering–Chukchi platform during eustatic sea‐level lowering. The restricted ice extent is also consistent with the output of climate models that simulate a lack of significant summer cooling. Copyright © 2008 John Wiley & Sons, Ltd.
    Type of Medium: Online Resource
    ISSN: 0267-8179 , 1099-1417
    URL: Issue
    URL: Article
    DOI: 10.1002/jqs.v23:6/7
    DOI: 10.1002/jqs.1196
    Language: English
    Publisher: Wiley
    Publication Date: 2008
    detail.hit.zdb_id: 2031875-3
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  • 4
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    Equilibrium‐line altitudes during the Last Glacial Maximum across the Brooks Range, Alaska
    Wiley ; 2005
    In:  Journal of Quaternary Science Vol. 20, No. 7-8 ( 2005-10), p. 821-838
    Details
    In: Journal of Quaternary Science, Wiley, Vol. 20, No. 7-8 ( 2005-10), p. 821-838
    Abstract: Equilibrium‐line altitudes (ELAs) were estimated for 383 reconstructed glaciers across the Brooks Range, northern Alaska, to investigate their regional pattern during the Last Glacial Maximum (LGM). Glacier outlines were delimited based on published field mapping and the original interpretations of aerial photographs. Glacier margins were digitised from 1:63 360‐scale maps into a geographic information system (GIS) with a digital elevation model on a 60‐m grid. ELAs were calculated for each reconstructed glacier using the accumulation area ratio method (AAR = 0.58). The analysis was restricted to relatively simple cirque and valley glaciers that deposited clearly identifiable LGM moraines, and that did not merge with the complex transection glacier ice that filled most troughs of the range. The glaciers used in this analysis had areas ranging from 0.14 to 120 km 2 . Their ELAs rose from 470 m a.s.l. in the western Brooks Range to 1860 m a.s.l. in the east, over a distance of 1000 km. The ELAs were fitted with a third‐order polynomial trend surface to model their distribution across the range, and to investigate the source of local‐scale variations. The trend surface lowers toward the west and south, similar to previously derived trends based on glaciation thresholds. In addition, ELAs in the northeastern part of the range lower northward toward the Beaufort Sea, which has not been reported as strongly in other studies. Modern glacier ELAs also lower toward the southwest. The depression of LGM ELAs from modern glacier ELAs is greatest in the central Brooks Range (a maximum of 700 m), and decreases to the east (200 m). The regional pattern of LGM ELAs points to the primary source of moisture from the North Pacific, as it is today. The unexpected trend of LGM ELAs in the northeast part of the range is supported by recent field mapping, where anomalous ice distribution and ELAs reflect complicated LGM climate patterns and possibly late Quaternary tectonism. Copyright © 2005 John Wiley & Sons, Ltd.
    Type of Medium: Online Resource
    ISSN: 0267-8179 , 1099-1417
    URL: Issue
    URL: Article
    DOI: 10.1002/jqs.v20:7/8
    DOI: 10.1002/jqs.980
    Language: English
    Publisher: Wiley
    Publication Date: 2005
    detail.hit.zdb_id: 2031875-3
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  • 5
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    Late Pleistocene and Holocene glaciation of the Fish Lake valley, northeastern Alaska Range, Alaska
    Wiley ; 2009
    In:  Journal of Quaternary Science Vol. 24, No. 7 ( 2009-10), p. 677-689
    Details
    In: Journal of Quaternary Science, Wiley, Vol. 24, No. 7 ( 2009-10), p. 677-689
    Type of Medium: Online Resource
    ISSN: 0267-8179 , 1099-1417
    URL: Issue
    URL: Article
    DOI: 10.1002/jqs.v24:7
    DOI: 10.1002/jqs.1279
    Language: English
    Publisher: Wiley
    Publication Date: 2009
    detail.hit.zdb_id: 2031875-3
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  • 6
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    Postglacial environmental change inferred from carbonate‐ and organic‐rich sediments of groundwater‐fed Kelly Lake, Kenai Peninsula, south‐central Alaska
    Wiley ; 2023
    In:  Journal of Quaternary Science
    Details
    In: Journal of Quaternary Science, Wiley
    Abstract: Major shifts in hydroclimate have been documented during the last deglacial period and the Holocene in south‐central Alaska. Rare freshwater calcium carbonate (marl) deposits in lakes on the Kenai Peninsula can be used to reconstruct past changes in hydroclimate, including the influence of groundwater inflow to lakes. Here, the postglacial sediment sequence from groundwater‐fed Kelly Lake (60.514°N, 150.374°W) was analyzed for multiple proxies including isotopes of carbon and oxygen in marl calcite (δ 13 C marl and δ 18 O marl ), and isotopes of carbon (ẟ 13 C OM ) and abundances of C and N in organic matter. Bulk sediment analyses include organic matter and calcium carbonate (CaCO 3 ) contents, visual stratigraphy and sediment flux. These analyses extend those of a previous paleoenvironmental reconstruction from Kelly Lake, which focused on sedimentary diatom oxygen isotopes and mass balance modeling over the past 10 000 years. Here, we show that Kelly Lake was deglaciated prior to 14.6 ka, and that by 14.0 ka marl dominated the sediments, with CaCO 3 precipitation probably driven by groundwater input and mediated by shallow‐water charophytes. Marl accumulation decreased as organic and clastic inputs increased between ~12.2 and 11.5 ka. This shift, together with an increase in both δ 13 C marl and δ 18 O marl values and a decrease in CaCO 3 content, indicates an increase in the influence of meteoric water on the hydrologic budget under wet conditions, possibly driven by a strengthened Aleutian Low atmospheric pressure cell. A shift to lower δ 13 C marl and δ 18 O marl values at ~11.5 ka is interpreted as an increase in the proportion of groundwater relative to meteoric water in the lake. Beginning around 9 ka, the proportion of meteoric water input continued to increase, the surrounding coniferous forest was established, and by 8 ka, CaCO 3 accumulation ended. Our results elucidate the environmental conditions under which marl was deposited during the Lateglacial and early Holocene in this part of Alaska, and demonstrate how a variety of synoptic‐ and local‐scale climatic variables can converge to influence sedimentation in a groundwater‐fed lake.
    Type of Medium: Online Resource
    ISSN: 0267-8179 , 1099-1417
    URL: Article
    DOI: 10.1002/jqs.3550
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2031875-3
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  • 7
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    Temporal and bathymetric resolution of nautiloid death assemblages in stratigraphically condensed oozes (New Caledonia)
    Wiley ; 2016
    In:  Terra Nova Vol. 28, No. 4 ( 2016-08), p. 271-278
    Details
    In: Terra Nova, Wiley, Vol. 28, No. 4 ( 2016-08), p. 271-278
    Abstract: Cephalopod shells can be affected by postmortem transport and biostratigraphic condensation, but direct estimates of the temporal and spatial resolutions of cephalopod assemblages are missing. Amino acid racemisation calibrated by 14 C demonstrates a centennial‐scale time averaging ( 〈 500 years) of Nautilus macromphalus in sediment‐starved, epi‐ and mesobathyal pelagic environments. The few shells that are thousands of years old are highly degraded. The median occurrence of dead shells is at 445 m depth, close to the 300–400 m depth where living N. macromphalus are most abundant. Therefore, dead shells of this species accumulate at a centennial temporal resolution and with excellent bathymetric fidelity. Dead Nautilus shells exist for only a few hundred years on the seafloor, in contrast to the biostratigraphically condensed mixture of extant foraminifers and foraminifers that went extinct during the Pleistocene. Cephalopod shells that do not show any signs of early diagenetic cementation are unlikely to be biostratigraphically condensed.
    Type of Medium: Online Resource
    ISSN: 0954-4879 , 1365-3121
    URL: Issue
    URL: Article
    DOI: 10.1111/ter.2016.28.issue-4
    DOI: 10.1111/ter.12218
    RVK:
    TE 1000
    Language: English
    Publisher: Wiley
    Publication Date: 2016
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    detail.hit.zdb_id: 2020958-7
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  • 8
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    Holocene climate inferred from glacier extent, lake sediment and tree rings at Goat Lake, Kenai Mountains, Alaska, USA
    Wiley ; 2009
    In:  Journal of Quaternary Science Vol. 24, No. 1 ( 2009-01), p. 33-45
    Details
    In: Journal of Quaternary Science, Wiley, Vol. 24, No. 1 ( 2009-01), p. 33-45
    Type of Medium: Online Resource
    ISSN: 0267-8179 , 1099-1417
    URL: Issue
    URL: Article
    DOI: 10.1002/jqs.v24:1
    DOI: 10.1002/jqs.1166
    Language: English
    Publisher: Wiley
    Publication Date: 2009
    detail.hit.zdb_id: 2031875-3
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  • 9
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    Late Quaternary tephrostratigraphy, Ahklun Mountains, SW Alaska
    Wiley ; 2012
    In:  Journal of Quaternary Science Vol. 27, No. 4 ( 2012-05), p. 344-359
    Details
    In: Journal of Quaternary Science, Wiley, Vol. 27, No. 4 ( 2012-05), p. 344-359
    Abstract: Radiocarbon‐dated sediment cores from six lakes in the Ahklun Mountains, south‐western Alaska, were used to interpolate the ages of late Quaternary tephra beds ranging in age from 25.4 to 0.4 ka. The lakes are located downwind of the Aleutian Arc and Alaska Peninsula volcanoes in the northern Bristol Bay area between 159° and 161°W at around 60°N. Sedimentation‐rate age models for each lake were based on a published spline‐fit procedure that uses Monte Carlo simulation to determine age model uncertainty. In all, 62 14 C ages were used to construct the six age models, including 23 ages presented here for the first time. The age model from Lone Spruce Pond is based on 18 ages, and is currently the best‐resolved Holocene age model available from the region, with an average 2σ age uncertainty of about ± 109 years over the past 14.5 ka. The sedimentary sequence from Lone Spruce Pond contains seven tephra beds, more than previously found in any other lake in the area. Of the 26 radiocarbon‐dated tephra beds at the six lakes and from a soil pit, seven are correlated between two or more sites based on their ages. The major‐element geochemistry of glass shards from most of these tephra beds supports the age‐based correlations. The remaining tephra beds appear to be present at only one site based on their unique geochemistry or age. The 5.8 ka tephra is similar to the widespread Aniakchak tephra [3.7 ± 0.2 (1σ) ka], but can be distinguished conclusively based on its trace‐element geochemistry. The 3.1 and 0.4 ka tephras have glass major‐ and trace‐element geochemical compositions indistinguishable from prominent Aniakchak tephra, and might represent redeposited beds. Only two tephra beds are found in all lakes: the Aniakchak tep hra (3.7 ± 0.2 ka) and Tephra B (6.1 ± 0.3 ka). The tephra beds can be used as chronostratigraphic markers for other sedimentary sequences in the region, including cores from Cascade and Sunday lakes, which were previously undated and were analyzed in this study to correlate with the new regional tephrostratigraphy. Copyright © 2012 John Wiley & Sons, Ltd.
    Type of Medium: Online Resource
    ISSN: 0267-8179 , 1099-1417
    URL: Issue
    URL: Article
    DOI: 10.1002/jqs.v27.4
    DOI: 10.1002/jqs.1552
    Language: English
    Publisher: Wiley
    Publication Date: 2012
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  • 10
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    Early and late Holocene glacial fluctuations and tephrostratigraphy, Cabin Lake, Alaska
    Wiley ; 2013
    In:  Journal of Quaternary Science Vol. 28, No. 8 ( 2013-11), p. 761-771
    Details
    In: Journal of Quaternary Science, Wiley, Vol. 28, No. 8 ( 2013-11), p. 761-771
    Abstract: Marked changes in sediment types deposited in Cabin Lake, near Cordova, Alaska, represent environmental shifts during the early and late Holocene, including fluctuations in the terminal position of Sheridan Glacier. Cabin Lake is situated to receive meltwater during periods when the outwash plain of the advancing Sheridan Glacier had aggraded. A brief early Holocene advance from 11.2 to 11.0 cal ka is represented by glacial rock flour near the base of the sediment core. Non‐glacial lake conditions were restored for about 1000 years before the water level in Cabin Lake lowered and the core site became a fen. The fen indicates drier‐than‐present conditions leading up to the Holocene thermal maximum. An unconformity spanning 5400 years during the mid‐Holocene is overlain by peat until 1110 CE when meltwater from Sheridan Glacier returned to the basin. Three intervals of an advanced Sheridan Glacier are recorded in the Cabin Lake sediments during the late Holocene: 1110–1180, 1260–1540 and 1610–1780 CE. The sedimentary sequence also contains the first five reported tephra deposits from the Copper River delta region, and their geochemical signatures suggest that the sources are the Cook Inlet volcanoes Redoubt, Augustine and Crater Peak, and possibly Mt Churchill in the Wrangell Volcanic field.
    Type of Medium: Online Resource
    ISSN: 0267-8179 , 1099-1417
    URL: Issue
    URL: Article
    DOI: 10.1002/jqs.v28.8
    DOI: 10.1002/jqs.2671
    Language: English
    Publisher: Wiley
    Publication Date: 2013
    detail.hit.zdb_id: 2031875-3
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