Consists of three units of Till and others (2011). First, their unit DCbm is dark-gray to black marble and subordinate impure fissile marble, calcareous schist, and mafic schist that is best exposed in sea cliffs along Norton Bay and in rubble-covered hills inland. Marble is in layers 1 to 20 cm thick and has rhythmically alternating purer, coarse-crystalline and more impure, fine-crystalline layers. Green-weathering, fine-grained chlorite, actinolite, albite, and white mica assemblages that Till and others (2011) interpreted to be mafic dikes, sills, and plugs intruding the carbonate rocks are common. Glaucophane inclusions are found in the albite. Till and others (2011) report that contact metamorphic effects are preserved, including bleached carbonate rocks and skarn assemblages. Mafic minerals also commonly form layers or are disseminated in the fine crystalline carbonate rocks, suggesting that some mafic volcanism accompanied deposition of the carbonate strata. Seven conodont faunas were obtained from six localities in this subunit. Two faunas are middle to early late Silurian, one is middle Early Devonian, and one is late Silurian to Early Devonian. Two faunas from westernmost exposures are considerably older: middle Early through Late Ordovician and Early Cambrian. Thus, there is a gap of over 100 million years between the oldest and youngest faunas; Till and others (2011) infer a number of scenarios to explain the gap, possibly involving limited collection and therefore missing intervals, hiatus, and (or) reworking of older units. The second of Till and others’ units (DObm) that we include in this unit consists of dark-gray to black metalimestone and marble and subordinate dolostone exposed in sea cliffs on Kotzebue Sound. “A 15- to 20-m-thick interval of dominantly matrix-supported carbonate breccia, with rounded and angular clasts as much as 5 m in diameter, occurs in the section, as well as thinner ( 1 m thick) intervals of carbonate-clast breccia. Local solution collapse features occur, and dedolomitization textures were seen in thin sections. Subordinate argillite, phyllite, and radiolarian chert are found about 2.4 km west of Cape Deceit; quartz-graphite schist and impure marble (containing as much as 20% graphite, quartz, albite, and white mica) are abundant in the western exposures” (Till and others, 2011). This subunit “has yielded tightly dated fossil collections of Middle Ordovician through late Silurian age and some longer ranging collections that could be as young as Devonian (Ryherd and Paris, 1987). The argillite-dominated interval west of Cape Deceit contains abundant Middle and Late Ordovician graptolite assemblages, as well as Ordovician conodonts (Ryherd and Paris, 1987; Harris and others, 1995; Ryherd and others, 1995; Dumoulin and others, 2002). Higher in the unit, a continuous section of allodapic carbonate rocks, at least several hundred meters thick, produced a middle to late Silurian (Wenlock to Ludlow) conodont succession (Dumoulin and others, 2002). Several conodont collections from eastern exposures of the unit could be as young as Devonian” (Till and others, 2011). Subunit three (Till and others’ [2011] unit D_ks) is a dark-brownish-gray, rust-spotted, well-foliated, medium-grained schist composed predominantly of quartz, calcite, white mica, chlorite, plagioclase, and graphite. It locally shows millimeter-scale dark to light layering. It is interlayered on a meter to kilometer scale with the other subunits upon which its age was assigned