Chukchi Margin: A Potential Target for Scientific (IODP) Drilling in the Western Arctic Ocean
Byrd Polar Research Center, Ohio State University, Columbus, OH.
The Chukchi margin is one of the most sensitive Arctic areas to climate variability and sea-level fluctuations. The Chukchi shelf and adjacent Arctic Ocean are affected by the Pacific water inflow via the Bering Strait, which influences sedimentary, hydrographic, biological, and ice conditions in this region. Sedimentary and hydrographic regimes in the western part of the Chukchi Sea are also under the influence of large eastern Siberian rivers. During glacial periods with low sea levels the exposed Chukchi shelf formed a broad land mass, known as Beringia, and separated the Arctic and Pacific oceans. While the overall Chukchi shelf is the area of net sediment erosion, except for canyon levee deposits and buried drainage channels, its northern margin features high sediment deposition, especially at the mouths of large canyons. Existing seismic-reflection data indicate a particularly large, up to 3,500-m thick sedimentary wedge at the mouth of the Herald Canyon (Jokat and Hegewald, 2010), the largest trough in the Chukchi region that receives sediment inputs from both the Pacific and Siberian sources. Drilling this sedimentary wedge would provide valuable material for addressing several topics critical for understanding depositional and paleoceanographic evolution of the Arctic Ocean, notably:
(1) impact of sea-level fluctuations on high-Arctic depositional system,
(2) history of the Pacific water inflow into the Arctic, and
(3) variability of Arctic sea ice in relation to climate changes.
Coring results from the Chukchi Alaskan margin indicate Holocene sedimentation rates exceeding 1 m/kyr, presumably driven by sediment load in dense waters cascading downslope and sea-ice melt (Darby et al., 2009). Even higher rates are likely for glacial times, when sea level was below the shelf break and the continental slope received sediment from the exposed shelf and extended rivers, combined with deposition originating from ice sheets. We can thus expect to recover a high-resolution (submillennial to subcentury scale) sedimentary record from the Herald Canyon mouth at least for the Quaternary to Pliocene section, when environments were comparable to those of recent times (open Bering Strait, frequent climatic and sea-level fluctuations). Offset drilling at more distal (northern) sites, where strata thin out, would recover a more extended time interval including a prominent late Oligocene-early Miocene sea-level fall and the bottom of the sedimentary wedge, respectively. In addition to drilling at the Herald Canyon mouth, buried channels on the Chukchi shelf can provide material for several intervals of Quaternary sedimentation history in the region. The combined shelf-to-slope IODP drilling at the Chukchi margin (proposal under development) will provide a logical extension of scientific drilling in the Bering Strait area and link it with the Arctic Ocean projects.
AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.��������������������������������������������������������������������������������������������������������