Defining the Timing and Extent of the Marine Transgression Following the Last Glacial Maximum in Southeastern Alaska

Baichtal, James F.; Carlson, Risa J.; Smith, Jane; Landwehr, Dennis J.

doi:10.1130/abs/2017am-298879

Cited by 2 publications

(5 citation statements)

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“…This would suggest a possible sea-level lowering by up to 175 m just inshore of the fault, which occurred just after the lowstand off Haida Gwaii. As proposed by Baichtal et al (2017aBaichtal et al ( , 2017b, the development of a forebulge that resulted in a maximum sea-level lowering of ~175 m would suggest persistent ice to the east within the mainland until ca. 11.5 ka.…”

Section: Research Papermentioning

confidence: 85%

“…A wave-cut terrace at 165 m water depth off the west coast of the Prince of Wales and Baranof Islands (Carlson, 2007) may correspond to the lowstand seen off Haida Gwaii. Baichtal et al (2017aBaichtal et al ( , 2017b suggested that a peripheral forebulge developed west of the ice front, similar to Haida Gwaii, starting at 16.9 ka, with most of the marine areas being deglaciated by 14.5 ka. Terraces mapped from multibeam bathymetry can be seen at 165-180 m water depth (Baichtal et al, 2017b).…”

Section: Sea-level Historymentioning

confidence: 95%

“…In addition, pahoehoe (subaerial) lava flows occur at water depths of 160 m offshore (Baichtal et al, 2017b). Within the island archipelago, sea level reached the highest levels of between 65 and 190 m sometime after 13.5 ka (Carlson and Baichtal, 2015;Baichtal et al, 2017aBaichtal et al, , 2017b.…”

Section: Sea-level Historymentioning

confidence: 99%

“…11.5 ka. Upon collapse of the forebulge, and coupled with eustatic sealevel rise, sea levels reached a maximum transgression on the outer islands between 11.5 and 10.6 ka (Carlson and Baichtal, 2015;Baichtal et al, 2017aBaichtal et al, , 2017b. Baichtal et al (2017b) presented a proposed sea-level curve for the region that complements the findings presented here.…”

Section: Research Papermentioning

confidence: 99%

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Late Quaternary sea level, isostatic response, and sediment dispersal along the Queen Charlotte fault

2021

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The active Pacific margin of the Haida Gwaii and southeast Alaska has been subject to vigorous storm activity, dramatic sea-level change, and active tectonism since glacial times. Glaciation was minimal along the western shelf margin, except for large ice streams that formed glacial valleys to the shelf break between the major islands of southeast Alaska and Haida Gwaii. Upon deglaciation, sediment discharge was extensive, but it terminated quickly due to rapid glacial retreat and sea-level lowering with the development of a glacio-isostatic forebulge, coupled with eustatic lowering. Glacial sedimentation offshore ended soon after 15.0 ka. The shelf became emergent, with sea level lowering by, and possibly greater than, 175 m. The rapid transgression that followed began sometime before 12.7 ka off Haida Gwaii and 12.0 ka off southeast Alaska, and with the extreme wave-dominated environment, the unconsolidated sediment that was left on the shelf was effectively removed. Temperate carbonate sands make up the few sediment deposits presently found on the shelf. The Queen Charlotte fault, which lies just below the shelf break for most of its length, was extensively gullied during this short period of significant sediment discharge, when sediment was transported though the glacial valleys and across the narrow shelf through fluvial and submarine channels and was deposited offshore as sea level dropped. The Queen Charlotte fault became the western terminus of the glacio-isostatic forebulge, with the fault acting as a hinged flap taking up the uplift and collapse along the fault of 70+ m. This may have resulted in the development of the distinctive fault valley that presently acts as a very linear channel pathway for sediment throughout the fault system.

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Section: Research Papermentioning

confidence: 85%

Section: Sea-level Historymentioning

confidence: 95%

Section: Sea-level Historymentioning

confidence: 99%

Section: Research Papermentioning

confidence: 99%

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Late Quaternary sea level, isostatic response, and sediment dispersal along the Queen Charlotte fault

2021

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“…Carlson and Baichtal (2015) first reported evidence of a forebulge along the western shore Prince of Wales Island from many of the islands immediately to the west. Baichtal et al (2017aBaichtal et al ( , 2017b further discussed and defined the forebulge and associated sea-level fluctuations. Our analysis has refined the timing and description of this forebulge.…”

Section: Collapse Of the Crustal Forebulgementioning

confidence: 99%

Late Pleistocene and early Holocene sea-level history and glacial retreat interpreted from shell-bearing marine deposits of southeastern Alaska, USA

Baichtal¹,

Lesnek

Carlson³

et al. 2021

Geosphere

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We leverage a data set of >720 shell-bearing marine deposits throughout southeastern Alaska (USA) to develop updated relative sea-level curves that span the past ∼14,000 yr. This data set includes site location, elevation, description when available, and 436 14C ages, 45 of which are published here for the first time. Our sea-level curves suggest a peripheral forebulge developed west of the retreating Cordilleran Ice Sheet (CIS) margin between ca. 17,000 and 10,800 calibrated yr B.P. By 14,870 ± 630 to 12,820 ± 340 cal. yr B.P., CIS margins had retreated from all of southeastern Alaska's fjords, channels, and passages. At this time, isolated or stranded ice caps existed on the islands, with alpine or tidewater glaciers in many valleys. Paleoshorelines up to 25 m above sea level mark the maximum elevation of transgression in the southern portion of the study region, which was achieved by 11,000 ± 390 to 10,500 ± 420 cal. yr B.P. The presence of Pacific sardine (Sardinops sagax) and the abundance of charcoal in sediments that date between 11,000 ± 390 and 7630 ± 90 cal. yr B.P. suggest that both ocean and air temperatures in southeastern Alaska were relatively warm in the early Holocene. The sea-level and paleoenvironmental reconstruction presented here can inform future investigations into the glacial, volcanic, and archaeological history of southeastern Alaska.

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Defining the Timing and Extent of the Marine Transgression Following the Last Glacial Maximum in Southeastern Alaska

Cited by 2 publications

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Late Quaternary sea level, isostatic response, and sediment dispersal along the Queen Charlotte fault

Late Quaternary sea level, isostatic response, and sediment dispersal along the Queen Charlotte fault

Late Pleistocene and early Holocene sea-level history and glacial retreat interpreted from shell-bearing marine deposits of southeastern Alaska, USA

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