A Skeleton in Triassic Rocks in the Brooks Range Foothills

Fragments of vertebrate fossils are found in beds of the Shublik Formation, which blanketed most of northern Alaska during Triassic time. Although articulated remains are uncommon, one partial skeleton was discovered in 1950 during exploration of Naval Petroleum Reserve No. 4. ... This note calls attention to the existence of the skeleton and reports on what has been observed of the vertebrate remains. Figs. 1 and 2 locate the site (68°37'15" N, 157°35' W) on Cutaway Creek (Howard Pass 1:250,000-scale quadrangle) in the geologically disturbed zone of the Brooks Range foothills. It is about 200 miles south of Point Barrow and 35 miles northwest of Howard Pass. Fig. 3 is a photograph of the actual bedding-plane exposure. Most of one side of the rib case is exposed, and some limb structures seem preserved. The exposed parts indicate a skeleton more than 5 feet long. Bone fragments are common in the fine talus weathering off the outcrop. Although no invertebrate fossils were seen on the surfaces of beds containing the skeleton, they are abundant in correlative beds; detailed examination of this or nearby exposures should yield pelecypods that will fix the biostratigraphic level of the vertebrate remains. Some features of the Late Triassic environment can be assessed. A sea of remarkably persistent character extended beyond the length of the present Brooks Range and probably more than twice the width of the present Arctic Slope. A shoreline existed near the present northeast coast of Alaska, but coarse detritus was not carried far southward. The bottom elsewhere was below wave base, and the sediment that settled onto it formed thin deposits, first of anaerobic chert, shale and limestone, then aerobic lithographic limestone. Pectens ... are abundant .... The thin chert beds surrounding the skeleton are correlative with beds elsewhere that contain Halabia of Karnian or early Norian age .... The skeleton is older than 200 million years as shown by K/Ar age determinations on minerals in diabase sills that intrude the Shublik Formation about 20 miles to the east .... Vertebrate fragments previously collected from the Shublik have been identified as follows: from this locality and from limestone near Hardway Creek (68°38'5" N, 156°51' W) about 20 miles to the east - vertebra of a possible ichthyosaur and teeth of a probable Mixasaurus ...; in limestone, chert, and shale on Kiligwa River (68°43'45" N, 158 °26' W) about 25 miles to the northwest - probable caudal vertebra of an ichthyosaur ...; and in limestone at the west end of the Sadlerochit Mountains (69°35'15" N, 145°55'5" W), northeastern Brooks Ranges - vertebral, costal, and jaw fragments of either the Shastasauridae or Ichthyosauridae ichthyosaur family .... Helicopters offer the only practical access to the site, for the nearest lake on which a float plane can land is more than 10 miles away. Transportation for preliminary inspection could probably be arranged with any geologic field party working within a hundred miles of the locality. Collection of the skeleton would require that an outfit be landed near the outcrop by ski plane in the spring and retrieved during the fall or winter. We cannot judge the quality or significance of the skeleton but feel that it should be examined by a vertebrate paleontologist as it could yield valuable information on life in the seas during Triassic time at a present arctic latitude

Temperatures and interval geothermal-gradient determinations from wells in National Petroleum Reserve in Alaska

Temperature and related records from 28 wells in the National Petroleum Reserve in Alaska (NPRA) although somewhat constrained from accuracy by data gathering methods, extrapolate to undisturbed formation temperatures at specific depths below permafrost, and lead to calculated geothermal graidents between these depths. Tabulation of the results show that extrapolated undisturbed temperatures range from a minimum of 98/sup 0/F (37/sup 0/C) at 4000 feet (1220 m) to a maximum of 420/sup 0/F (216/sup 0/C) at 20,260 feet (6177 m) and that geothermal gradients range from 0.34/sup 0/F/100' (6/sup 0/C/km) between 4470 feet to 7975 feet (Lisburne No. 1) and 3.15/sup 0/F/100' (57/sup 0/C/km) between 6830 feet to 7940 feet (Drew Point No. 1). Essential information needed for extrapolations consists of: time-sequential bottom-hole temperatures during wire-line logging of intermediate and deep intervals of the borehole; the times that circulating drilling fluids had disturbed the formations; and the subsequent times that non-circulating drilling fluids had been in contact with the formation. In several wells presumed near direct measures of rock temperatures recorded from formation fluids recovered by drill stem tests (DST) across thin (approx. 10-20 foot) intervals are made available. We believe that the results approach actual values close enough to serve as approximations of the thermal regimes in appropriate future investigations. Continuous temperature logs obtained at the start and end of final logging operations, conductivity measurements, and relatively long-term measurements of the recovery from disturbance at shallow depths in many of the wells will permit refinements of our values and provide determination of temperatures at other depths. 4 references, 6 figures, 3 tables