A NORTHERN PALEOLATITUDE ECHINODERM FAUNA FROM THE MISSISSIPPIAN LISBURNE GROUP OF ARCTIC ALASKA: PRELIMINARY PALEONTOLOGIC AND STRATIGRAPHIC CHARACTERIZATION

The Lisburne Group is an extensive (up to ~700 m thick) carbonate-dominated Carboniferous sequence that extends throughout much of the northern Brooks Range of Arctic Alaska. It is part of an allochthonous sequence that makes up the Arctic terrane of northern Alaska and is interpreted to have accumulated in a shallow sea along the margin of the Arctic terrane between Siberia and Laurentia. As a result, the Lisburne Group represents a unique paleogeographic region from a northern paleolatitude, making it noteworthy from a paleontologic and paleobiogeographic perspective. Although a diverse macroinvertebrate fauna has been reported from the Lisburne Group, including abundant crinoid and blastoid echinoderms, most of the faunal constituents remain undescribed. Likewise, detailed stratigraphic investigations have not yet been conducted in most regions where the Lisburne group is exposed; instead, most studies of surficial Lisburne Group exposures to date have focused on establishing the sequence of major stratigraphic units and their relationships across the Brooks Range as a whole.

We conducted a reconnaissance field investigation of the stratigraphy and faunal components of the Lisburne Group (Mississippian) in the vicinity of Galbraith Lake (northcentral Brooks Range, Alaska). The primary goals of this investigation were to (1) locate previously described fossiliferous horizons, (2) construct detailed stratigraphic sections for the region, (3) constrain the ages of fossiliferous horizons, and (4) collect echinoderm specimens for taxonomic evaluation. Here, we summarize preliminary findings and interpretations of the stratigraphic context, age, and faunal constituents of fossiliferous horizons in the study area. This work has broader implications for better understanding Mississippian echinoderm assemblages, particularly those from northern paleolatitudes. It will also facilitate comparison of paleoenvironmental conditions, community structure, and evolutionary patterns between echinoderm faunas from northern paleolatitudes and those from southern or equatorial paleogeographic regions (e.g., the midcontinent of North America).