INVESTIGATION OF LOWER MISSISSIPPIAN STRATA FROM THE NORTHCENTRAL BROOKS RANGE OF ALASKA: PRELIMINARY STRATIGRAPHIC AND PALEONTOLOGIC CHARACTERIZATION

The Lisburne Group is an extensive (up to ~700 m thick) sequence of predominantly Carboniferous rocks that extends throughout much of the northern Brooks Range, Alaska. It is primarily composed of carbonate rocks and is part of an allochthonous sequence that makes up the Arctic terrane of northern Alaska. The sequence is interpreted to have accumulated in a shallow sea along the margin of the Arctic terrane when it was located between Siberia and Laurentia. As a result, the Lisburne Group represents a unique paleogeographic region from a northern paleolatitude, making it notable from a paleontologic and paleobiogeographic perspective.

Studies of the Lisburne Group in surficial exposures have primarily focused on establishing the stratigraphic sequence of units and their relationships across the Brooks Range. Because of its great lateral extent, however, detailed stratigraphic and faunal investigations have not yet been conducted in most regions where the Lisburne Group is exposed. For example, although the Lisburne Group is known to contain a diverse macroinvertebrate fauna (especially crinoid and blastoid echinoderms), most of the faunal constituents remain undescribed.

We conducted an investigation of the stratigraphy and faunal components of the Lisburne Group (Mississippian) in the vicinity of Galbraith Lake (northcentral Brooks Range, Alaska). Here, we summarize preliminary findings and interpretations of the sequence stratigraphy, sedimentology, and fossil content of the study area. This work has broader implications for better understanding paleoenvironmental and paleoecological conditions of high-latitude Mississippian carbonate environments and for comparing faunal and sedimentological history between high-latitude and low-latitude paleogeographic regions (e.g., those in the midcontinent of North America).