Significant stratigraphic and structural variations occur within the Carboniferous Endicott and Lisburne Groups in the western Sadlerochit and Shublik Mountains. My detailed stratigraphic study distinguished vertical and lateral facies changes which occur within the Lisburne Group. The Kayak Shale thins depositionally over the Sadlerochit Mountains indicating that this important transitional area represents a major paleotopographic high. Geological mapping studies documented structural and stratigraphic variations, focusing on contact relationships between these units.

In the northeastern Brooks Range, the transgressive Endicott Group unconformably overlies the pre-Mississippian Franklinian sequence, composed primarily of the Precambrian Katakturuk Dolomite in the study area. The Kekiktuk Conglomerate at the base of the Endicott Group is highly variable, both texturally and compositionally. These variations reflect a complex paleo-topographic surface on which the Endicott Group was deposited. In the study area, the Kekiktuk Conglomerate shows significant variations in lithology, including orthoquartzite, carbonate-clast and quartz/chert pebble-clast conglomerates. Abrupt facies changes suggest that the Kekiktuk Conglomerate was deposited in a fluvial-dominated environment. The carbonate-clast conglomerates are lag deposits derived from the underlying Katakturuk Dolomite whereas the orthoquartzite and quartz/chert pebble conglomerate were transported into the area from an unknown source of siliciclastic sediment. The Kekiktuk Conglomerate forms a fining-upwards sequence grading into the Kayak Shale.

The Kayak Shale is composed primarily of fissile black shale in the Shublik Mountains. In the western Sadlerochit Mountains, it is compositionally variable and consists of black shale, siltstone and locally argillaceous limestones and dolostones transitional into the Lisburne Group. The Kayak Shale was deposited during a Late Mississippian marine transgression which lapped northward onto a regional high in the Sadlerochit Mountains area. The black shales of the Kayak Shale thin over this paleo-topographic high and do not exist across most of the Sadlerochit Mountains. Argillaceous limestones and dolostones of the Kayak Shale grade upwards into clean carbonates of the basal Lisburne Group, marking the continued transgression from terrigenous to carbonate sedimentation.

In addition to its paleogeographic importance, the Kayak Shale played a major role in the tectonic deformation of region. In the Shublik Mountains, the Kayak Shale forms a major detachment horizon above which the Lisburne Group and younger rocks are deformed by detachment folding. In the Sadlerochit Mountains, where the incompetent black shales of the Kayak Shale are discontinuous, no detachment exists and the Lisburne Group was deformed by small-displacement, high-angle reverse faults which originated as bedding parallel slip in the pre-Mississippian rocks.

Several shallowing-upward cycles of varying magnitudes are recorded within the carbonates of the Lisburne Group. Rocks of the lower Alapah Limestone show evidence of three classic shallowing-upwards cycles. A typical cycle grades upward from open platform skeletal packstones and grainstones into restricted platform wackestones and intertidal mudstones. Each cycle is capped by a thin veneer of terrigenous shale, siltstone, and/or sandstone.

The lower Alapah passes gradationally upward into the upper Alapah Limestone, representing a large-scale progradational sequence. Open platform skeletal packstones and grainstones are gradationally overlain by restricted platform peloidal-spiculitic wackestones and mudstones and intertidal sediments rich in algal material and evaporites. Near the top of the upper Alapah Limestone, a pervasive recrystallized zone exists and may be the result of subaerial exposure of the carbonate platform prior to deposition of the Wahoo Limestone.

Abruptly overlying the Alapah Limestone are the open- marine skeletal packstones and grainstones of the lower Wahoo Limestone. In outcrop, three massive cliffs record large-scale incomplete shallowing-upwards sequences. Each lithologic cycle is composed primarily of a thick sequence of subtidal skeletal packstones and grainstones and is capped by thin intervals of skeletal wackestones and lime mudstones which formed in more restricted environments.

In addition to direct evidence from the shallowing-upward lithologic cycles, diagenetic characteristics also indicate repeated transgressive-regressive events occurred during deposition of the Lisburne Group. Transgressive grainstones show little evidence of subaerial diagenesis and are dominated by burial diagenesis as indicated by evidence of pressure solution. The fabric in regressive grainstones is loosely packed because grains were stabilized by early cements that formed in response to subaerial diagenesis during regressions. Thus, both primary lithologies and secondary diagenetic signatures suggest multiple changes in sea level occurred through the evolution of the Lisburne Group carbonate platform.