Gulf of Alaska continental slope morphology: Evidence for recent trough mouth fan formation

Abstract

Glaciated continental shelves are host to numerous morphologic features that help understand past glacier dynamics. Southeastern Alaska is home to the St. Elias mountains, an active orogen that also hosts temperate marine glaciers. During glacial periods ice streams advance across the continental shelf, carving shelf-crossing troughs that reach the shelf edge. We use high-resolution multibeam data to develop the relationship between the Yakutat and Alsek Sea Valleys and the resulting continental slope morphology. The shelf and slope geomorphology can be divided into statistical groupings that relate to the relative balance of erosion and deposition. Our analysis indicates that only the Yakutat system has been able to build an incipient trough-mouth fan. The extreme sediment supply from this region was able to overwhelm the steep initial topography of the transform margin while further to the east sediment slope-bypass dominates. This analysis provides an extreme end member to existing studies of temperate glaciation along continental margins. The unique interplay between rapid uplift due to ongoing collision and the massive erosion caused by temperate glaciers provides for sedimentary flux far above most other systems.

Neogene to Quaternary stratigraphic evolution of the Antarctic Peninsula, Pacific Margin offshore of Adelaide Island: Transitions from a non-glacial, through glacially-influenced to a fully glacial state

“…Trough migration causes this area to differ from other regions of the PMAP and disrupts the relationship between the two major troughs along shelf, rise CCSs and inter-trough areas. Probably that migration if the reason because there is not a mature trough mouth fans identified in front of other glacial troughs (O´Cofaigh et al, 2003(O´Cofaigh et al, , 2016Laberg et al, 2010;Swartz et al, 2015). It also affects inter-trough areas with major drifts along the rise, as was observed by Rebesco et al (2002) and Amblas et al (2006) for north and south areas.…”

Controls on submarine channel-modifying processes identified through morphometric scaling relationships

“…2 and 3): (1) channel 1 of the Amazon fan, offshore northeast Brazil in the Atlantic Ocean (Pirmez and Imran, 2003), (2) channel 1 of the Bengal fan, in the Bay of Bengal in the northeastern Indian Ocean (Schwenk et al, 2003), (3) channel 12 of the eastern Gulf of Mexico, off the southern coast of the USA (Posamentier, 2003), and (4) channel 9 of the Niger Delta continental slope, offshore Nigeria in the Atlantic Ocean (hereafter called the "Niger slope"; Pirmez et al, 2000;Jobe et al, 2015). We also briefly discuss glacially influenced channels in the Gulf of Alaska, offshore the southern coasts of Alaska, USA and Canada in the Pacific Ocean, which are exceptionally large (up to 18 km wide and 300 m deep; Swartz et al, 2015). We also document dozens of smaller, isolated channel segments captured in the multibeam bathymetry from a single ship track (Amazon and Bengal channels) and relatively short, slope-confined channels lacking any visible connection to a submarine canyon or shallow marine sediment source (western Gulf of Mexico, northwestern Niger slope channels).…”

“…5 and 6) implies some component of allogenic, system-specific forcings on width. The Amazon, Bengal, and Gulf of Alaska channels exhibit the largest dimensions, possibly related to the large water and sediment discharge supplied to these systems (Milliman and Meade, 1983;Ludwig and Probst, 1998;Swartz et al, 2015), although the relationship between channel dimensions and catchment parameters is not yet clear (Sømme et al, 2009;Pettinga et al, 2018). The four highlighted channels in this study each display distinct width and/or depth trends with downstream distance, although all except the GoM 12 channel show overall increasing aspect ratio downstream.…”

Sediment controls dynamic behavior of a Cordilleran Ice Stream at the Last Glacial Maximum

“…At the Last Glacial Maximum (LGM) (occurring from 26.5 to 19 ka cal BP 14 ), the Cordilleran ice sheet discharged to the NE Pacific via ice streams through eight shelf-crossing sea valleys on the southern Alaskan margin [15][16][17][18] . Today, Bering Glacier is grounded on land, seaward of the St. Elias Mountains and Bagley Icefield and comprises 15% of the glacier ice in Alaska 19 (Fig.…”