Southwest Alaska Research Articles

Population growth and status of the Nushagak Peninsula caribou herd in southwest Alaska following reintroduction, 1988 - 1993

Caribou were reintroduced to the Nushagak Peninsula, Alaska in February 1988, after an absence of over 100 years. The purpose was to reestablish caribou in the area and once again provide hunting to local residents. The Nushagak Peninsula caribou herd (NPCH) has grown rapidly from 146 reintroduced caribou to over 1000 in 6 years at an exponential rate of increase of r = 0.317 or about 38%. The dramatic growth of the herd was attributed to the initial high percentage of females in the herd, high calf production and survival, pristine range, few predators and no hunting. Abundant high quality forage on the Nushagak Peninsula is the probable reason for the enhanced body condition and high natality even among 2-year-olds, and it has most likely contributed to the high calf survival and recruitment. Lack of predators and hunting has allowed calf and adult mortality to remain low. Although the size of the NPCH has grown steadily over the past 6 years, no significant dispersal from the peninsula has occurred. The population density of the NPCH was estimated to be 1.0/km2 in 1993. We believe the herd will continue to grow, and could reach a density of 2.3/km2 by 1998, even with a 10% harvest beginning in 1995. While the current growth of the NPCH makes the réintroduction a success, the increasing density, lack of dispersal and potential for over-grazing, presents managers with hard decisions.

A catastrophic flood caused by drainage of a caldera lake at Aniakchak Volcano, Alaska, and implications for volcanic hazards assessment

Aniakchak caldera, located on the Alaska Peninsula of southwest Alaska, formerly contained a large lake (estimated volume 3.7 × 10 9 m 3 ) that rapidly drained as a result of failure of the caldera rim sometime after ca. 3400 yr B.P. The peak discharge of the resulting flood was estimated using three methods: (1) flow-competence equations, (2) step-backwater modeling, and (3) a dam-break model. The results of the dam-break model indicate that the peak discharge at the breach in the caldera rim was at least 7.7 × 10 4 m 3 s −1 , and the maximum possible discharge was ≈1.1 × 10 6 m 3 s −1 . Flow-competence estimates of discharge, based on the largest boulders transported by the flood, indicate that the peak discharge values, which were a few kilometers downstream of the breach, ranged from 6.4 × 10 5 to 4.8 × 10 6 m 3 s −1 . Similar but less variable results were obtained by step-backwater modeling. Finally, discharge estimates based on regression equations relating peak discharge to the volume and depth of the impounded water, although limited by constraining assumptions, provide results within the range of values determined by the other methods. The discovery and documentation of a flood, caused by the failure of the caldera rim at Aniakchak caldera, underscore the significance and associated hydrologic hazards of potential large floods at other lake-filled calderas.

Always Getting Ready, Upterrlainarluta: Yup’ik Eskimo Subsistence in Southwest Alaska, by James H. Barker

Always Getting Ready, Upterrlainarluta: Yup’ik Eskimo Subsistence in Southwest Alaska, by James H. Barker

Always getting ready: Upterrlainarluta: Yup'ik eskimo subsistence in southwest Alaska

Always getting ready: Upterrlainarluta: Yup'ik eskimo subsistence in southwest Alaska

Denali Fault System of southern Alaska: An interior strike‐slip structure responding to dextral and sinistral shear coupling

The Denali fault system (DFS) extends for ∼1200 km, from southeast to south central Alaska. The DFS has been generally regarded as a right‐lateral strike‐slip fault, along which post late Mesozoic offsets of up to 400 km have been suggested. The offset history of the DFS is relatively unconstrained, particularly at its western end. For this study we calculated relative motion vectors at discrete points along the length of the DFS, based on the well‐understood kinematic interaction between the North American, Pacific, and Kula plates, and the following assumptions: (1) The arcuate geometry of the DFS has existed essentially unchanged since the Late Cretaceous; (2) The Yukon‐Tanana terrane and other terranes north of the DFS were fixed, in situ, prior to the accretion of the southern Alaskan terranes; and (3) Tangential and normal relative motion vector components calculated for points along the DFS using the plate model of Kelley [1993] describe the plate kinematics of the DFS since the Late Cretaceous. The consequent kinematic model for the DFS predicts that left‐lateral stresses have acted upon the western end of the DFS for much of its history, and conflicting senses of shear exist between the eastern and western ends of the system. The offset history of the western end of the Denali fault system should be significantly different than the history of the central and eastern sections; consequently, individual crustal blocks in southeast and southwest Alaska may have undergone, respectively, clockwise and counterclockwise rotations. The sense of rotation predicted by our model is in agreement with rotations determined by paleomagnetic studies and provides an alternative model to the “Alaskan orocline” hypotheses.

Stratigraphic Context of Old Crow Tephra, Holitna Lowland, Interior Southwest Alaska

A thick deposit of Old Crow tephra was discovered in a bluff exposure along the middle Holitna River near the Kulukbuk Hills (61°20′N latitude, 157°10′W longitude) in interior southwest Alaska. This locality is the southwesternmost-known deposit of Old Crow tephra in Alaska. Thickness and grain-size data from this site support a source volcano in the eastern Aleutian arc. Pleistocene stratigraphic sequences in the lowland are dominated by upward-fining eolian sand-sheet deposits and loess separated by organic silt. These deposits record at least two episodes of regional glaciation and an intervening nonglacial period (marine oxygen isotope stage 3, stage 5, or both). Old Crow tephra crops out near the top of the lower upward-fining eolian unit, indicating that the ash erupted near the end of an interval of periglacial eolian sedimentation. The sequence of eolian deposits that contain Old Crow tephra probably accumulated during the latter part of marine oxygen isotope stage 6, whereas the overlying eolian sequence formed during the last glaciation (stage 2). This stratigraphic position is consistent with other stratigraphic contexts for the tephra and with fission-track and thermoluminescence ages of ca. 140,000 ± 10,000 yr B.P.

Sandstone Petrography and Diagenesis of Lower Tertiary Sedimentary Rocks Along the Eastern Shore of Katmai National Park, Southwest Alaska

Sandstone Petrography and Diagenesis of Lower Tertiary Sedimentary Rocks Along the Eastern Shore of Katmai National Park, Southwest Alaska

Characteristics of Lower Tertiary Sedimentary Rocks Along the Eastern Shore of Katmai National Park, Southwest Alaska

Characteristics of Lower Tertiary Sedimentary Rocks Along the Eastern Shore of Katmai National Park, Southwest Alaska

Paleoshorelines and prehistory: an investigation of method

Preface. Introduction. PART I: STABLE LAND. ISLANDS. Introduction. Lucayan Settlement Patterns and Recent Coastal Changes in the Bahamas. Paleoshorelines and the Prehistory of Barbuda, West Indies. MAINLAND. Introduction. A Geoarchaeological Methodology for Studying Prograding Coastal Sequences: Beach Ridge Geomorphology in Kotzebue Sound, Alaska. Paleoshorelines and the Sambaquis of Brazil. UNDERWATER. Introduction. Recent Archaeogeophysical Studies of Paleoshorelines of the Gulf of Mexico. Inundated Prehistoric Sites in Apalachee Bay, Florida and the Search for the Clovis Shoreline. PART II: UNSTABLE LAND. ISLANDS. Introduction. Modeling Paleoshorelines in Geologically Active Regions: Applications to the Shumagin Islands, Southwest Alaska. Paleoshorelines and Prehistoric Settlement on Simeonof and Chernabura Islands, Outer Shumagin Islands, Alaska. MAINLAND. Introduction. Postglacial Relative Sea Level History of the Labrador Coast and the Interpretation of the Archaeological Record. Space Shuttle Imagery of Recent Catastrophic Change Along the Arid Andean Coast. CONCLUSION. GLOSSARY. BIBLIOGRAPHY. INDEX.

The August 18 eruption of Mt. Spurr

A brief explosive eruption of Mt. Spurr in southwest Alaska occurred on August 18, with little or no apparent precursory seismicity. Preliminary data suggested that the August 18 activity was similar to somewhat stronger than the previous explosive episode, on June 27 (see last 3 Bulletins). The June 27 ash had been carried north, away from nearby populated areas, but the August 18 ash fell on Anchorage, Alaska's largest city, 130 km east of Spurr, closing its internatioal airport and forcing most of its residents indoors.The eruption was first reported at 1548 (all times are local: UT −8 hours) by an airplane pilot who saw a dark cloud, probably an ash plume, breaking through weather clouds. About 8 minutes of seismicity at slightly above background preceded the pilot report. No lightning pulses, which often accompany ash eruptions, were detected, but there were additional pilot reports of ash during the next half‐hour. Seismicity increased markedly at 1641, and by 1645, NOAA C‐band radar had detected a plume to almost 11 km altitude. The National Weather Service released a SIGMET, warning pilots of the ash plume, at 1653.

Results of Instrument Neutron-Activation Trace-Element Analysis of Human Remains from the Naknek Region, Southwest Alaska

An attempt to replicate results of a previous dietary trace-element study of northwestern Alaska (Connor and Slaughter 1984) was made with human- and animal-bone samples from the Naknek region, southwest Alaska. Trace elements of special interest are strontium and zinc because of previously postulated relation of abundances of these elements to marine and terrestrial dietary foci in human remains from archaeological sites (i.e., Nelson et al. 1986; Schoeninger and Peebles 1981). Related objectives were to develop evidence supporting Harritt's (1988) proposal for the existence of separate late prehistoric inland and coastal social and territorial entities in the region, which would be reflected as a dichotomy of trace levels in human bone; differences in abundances of strontium and zinc trace elements in bones representing each group should reflect diets based on either terrestrial fauna and plants or largely of marine sea mammals and shellfish. We find that there are no characteristic trace-element patterns for differentiating historic and late prehistoric coastal or interior inhabitants of the Alaska Peninsula, in spite of historic and archaeological evidence that indicates that such patterns should be present. This lack of patterning is traced to an erroneous assumption made initially by the present authors, and by Connor and Slaughter (1984): Because 99 percent of all digested Sr is deposited in the skeleton of vertebrates (including marine), there is no direct correlation between Sr content of human bones and the proportion of sea-mammal or teleost consumption in the prehistoric human diet.

A Chemical Survey of Remote Lakes of the Alagnak and Naknek River Systems, Southwest Alaska, U.S.A.

of the largest lakes in the state. Formed or modified by glaciation during the Pleistocene, most of these lakes are found at low elevations (<300 m) along the northern slope of the Aleutian Range. Igneous rocks from the Middle Jurraisic and Tertiary periods intrude older sedimentary formations in this region, cre- ating lake basins of heterogeneous parent materials, particularly Abstract An analysis of the chemistry of 12 remote lakes of the Naknek and Alagnak drainages demonstrated significant differences in surface water alkalinity, due in part to high concentrations of naturally-occurring sulfate in the Alagnak drainage. The average surface water alkalinity for lakes in the Alagnak drainage (109 ueq L-') is much less than that for the Naknek drainage (425 ueq L-l), and below that for lakes from South Central Alaska, indicating a potential sensitivity of the lakes in the Alagnak river system to acid depostion. The upper Alagnak drainage contains Iron Springs Lake, a naturally acidic lake (pH 3.65) with a surface area of 70 ha. The acidity of this lake may be due to oxidation of surficial iron sulfide deposits, which would also explain the relatively high sulfate concentrations (120- 1516 jueq L-') in the Alagnak drainage.

A Chemical Survey of Remote Lakes of the Alagnak and Naknek River Systems, Southwest Alaska, U.S.A.

A Chemical Survey of Remote Lakes of the Alagnak and Naknek River Systems, Southwest Alaska, U.S.A.

Fossil Pollen and Insect Evidence for Postglacial Environmental Conditions, Nushagak and Holitna Lowland Regions, Southwest Alaska

This paper discusses the results of pollen and insect analyses of postglacial samples from the Nushagak and Holitna lowlands, southwest Alaska. Although radiocarbon dating control is poor, the samples can be arranged in a relative-age sequence based on stratigraphic occurrence. The fossil pollen data record the regional transition from a late-glacial dry graminoid tundra through the postglacial Birch, Alder, and Spruce zones. The lack of xeric insect species in the early postglacial suggests that the lowlands of southwest Alaska experienced maritime climatic conditions, in contrast to the interior. Rapid climatic warming is subsequently indicated by the fossil insect data, although the arrival of alder in the region postdates 8500 yr BP. There is no evidence for coniferous forest in the Nushagak lowland at any time in the postglacial, although spruce arrived in the Holitna lowland in the mid-postglacial.Key words: pollen analysis, fossil insects, paleoenvironments, postglacial, southwest Alaska

Effects of Age, Breast Feeding, and Household Structure on Haemophilus influenzae Type b Disease Risk and Antibody Acquisition in Alaskan Eskimos

Invasive Haemophilus influenzae type b (Hib) disease occurs with unusually high incidence in Alaskan Eskimos. In 1983, the authors evaluated the unique susceptibility of the Yupik-speaking Eskimo population in southwest Alaska. A matched case-control design was used to assess the influence of age, breast feeding, and household composition on disease risk, with a historical cohort design to evaluate their effects on acquisition of Hib anticapsular antibody. The authors studied 103 cases with known invasive Hib disease that occurred at a mean age of 8.7 +/- 8.6 months; healthy controls were matched for age and village of residence. Living in extended families at the time of disease onset was significantly associated with Hib disease (p less than 0.04; odds ratio = 1.8; 95% confidence interval 0.87-3.25). The authors found that breast feeding was significantly less common among cases than controls (p less than 0.03; odds ratio = 0.53; 95% confidence interval 0.27-0.98). Although there was a positive correlation between age and acquired level of total anticapsular antibody (r = 0.59; p less than 0.0001), previous exposure to invasive Hib disease did not influence these levels. Household crowding and breast feeding also did not appear to affect Hib antibody acquisition.

Toward a Culturally Based Pedagogy: A Case Study of One Yup'ik Eskimo Teacher

This case study is part of an ongoing collaborative research project with Yup'ik teachers in southwest Alaska. On the surface, this lesson appears to be an art lesson, but a cultural interpretation suggests it is about subsistence and survival. Implicit in this case for minority education is the importance of adapting social interactions, knowledge, and values toward the minority culture as one possible means for improving schooling.

Russian Exploration in Southwest Alaska: The Travel Journals of Petr Korsakovskiy (1818) and Ivan Ya Vasilev (1829)

Russian Exploration in Southwest Alaska: The Travel Journals of Petr Korsakovskiy (1818) and Ivan Ya Vasilev (1829)

The last interglaciation in Alaska: Stratigraphy and paleoecology of potential sites

At least 20 localities in Alaska contain deposits that may provide information on the last interglaciation (Oxygen-Isotope Substage 5e). These widely dispersed localities include river bluffs, coastal bluffs and terraces, elevated marine shorelines, lake basins, and artificial excavations. Most of the inferred interglacial deposits contain macrofossils or pollen that are older than the range of radiocarbon dating and commonly indicate climate as warm as or warmer than the present. At a few localities, evidence for deep thaw of permafrost also indicates a warm paleoclimate. At eight localities, the Old Crow tephra occurs at or below organic deposits that may represent Substage 5e. The tephra occurs beneath conspicuous organic deposits at Fairbanks, the Yukon Palisades, and Holitna lowland, and directly above a peat bed at Hogatza Mine. At Birch Creek, Halfway House, Ky-11, and Imuruk Lake, the tephra occurs within a paleosol or organic deposit, but other organic horizons that more likely indicate interglacial conditions occur at higher stratigraphic levels. The varied stratigraphic relations of the Old Crow tephra suggest that it may have been deposited close to the boundary between Isotope Substages 6 and 5, which is dated at about 130 ka in the marine record and between 132 and 140 ka on land. These age relations suggests that the tephra may have been deposited about 135 ± 5 ka, validating the recent fission-track age determination of 140 ± 10 ka for this deposit. Six coastal localities contain deposits of probable interglacial age, and these commonly are associated with evidence for eustatic sea levels higher than those of the present. Beach and sublittoral sediments of the Pelukian transgression occur up to 12 m asl along the northwest coast of Alaska, and are correlative with barrier island and lagoonal sediments on the Alaskan Arctic Coastal Plain. Both sets of deposits commonly contain extralimital mollusks and microfauna that indicate marine water slightly warmer than present and suggest that seasonal sea ice did not extend south of Bering Strait during the last interglacial as it does today. Farther south, elevated marine-terrace deposits on Amchitka Island contain marine invertebrates that indicate a climate warmer than at present. Peat horizons in coastal exposure at Goose Bay and coastal terraces at Lituya Bay contain pollen spectra that suggest forests like those of the present day, and spruce macrofossils exposed on Baldwin Peninsula indicate boreal forest more extensive than at present. Sediments from several lakes in northwestern Alaska may contain continuous records of the last interglaciation. A major warm interval, possibly Isotope Substage 5e, has been identified in a core from Squirrel Lake by a peak in Picea pollen that indicates forest extension beyond present limits. Similar pollen records are potentially available from two maars which formed in the Cape Espenberg area more than 125 ka. Terrestrial organic deposits thought to record the last interglaciation occur interstratified with marine and glaciogenic sediments in the Nushagak Lowland of southwest Alaska and on Baldwin Peninsula in Kotzebue Sound. Extensive exposures along the Copper and Nenana Rivers may also contain organic deposits that record the last interglaciation.

The character and distribution of mineralized fractures in the Kodiak Formation, Alaska: Implications for fluid flow in an underthrust sequence

The Kodiak Formation, an accreted slate belt in southwest Alaska, experienced two major episodes of fracturing and mineralization in the Late Cretaceous‐early Tertiary. The earlier of these episodes is related to underthrusting of sediments below a major décollement (D1), whereas a later episode is marked by development of fold and thrust structures and a regionally pervasive slaty cleavage within the accretionary wedge (D2). D1 veins are restricted to sand layers and are concentrated at the highest structural level of the Kodiak Formation. The most pervasive D1 fractures occur within a mélange zone, where the Kodiak Formation is thrust beneath the older Uyak Complex. Microstructures in the mélange suggest that these veins formed during the later stages of a deformation that involved layer parallel shear in conjunction with progressive lithification. D2 veins cut sand and shale layers and are concentrated at the lowest structural levels of the Kodiak Formation. Microstructures within these veins indicate that D2 veins are hydrofractures that were either (1) intermittentiy sealed along the length of the crack (e.g., in the smallest veins (&lt;0.5 cm width)), (2) intermittently sealed at asperities along the fracture surface, or (3) open along the length of the crack through most of the vein history (e.g., in the largest veins (&gt;0.5 cm width)). Fracturing coincided with development of a slaty cleavage in a regime of progressive simple shear. From highest to lowest structural levels, there is a gradual increase in measured finite strain, the abrupt appearance of pervasive D2 veins, and a greater noncoaxiality of strain related to southeast directed thrusting. These observations suggest that D2 veins formed above a décollement that was active at the base of a Late Cretaceous‐early Tertiary accreted package. In total, the D1 and D2 veins suggest substantial fluid flow within an ancient subduction complex, with development of hydrofractures first in the footwall and then in the hanging wall of a basal décollement that stepped from shallow to deeper structural levels.

Evidence for a weak and overpressured décollement beneath sediment‐dominated accretionary prisms

We present structural data from several underthrust sequences in southwest Alaska that suggest that the deformation regime beneath accretionary prisms is characterized by a subvertical σ1 and regionally extensive layer‐parallel shearing. These results contrast markedly with the results obtained from the more shallow parts of accretionary prisms and fold and thrust belts where σ1 plunges gently seaward or toward the deformation front. On the basis of Mohr circle diagrams, we propose that these different stress directions are consistent only with a model in which the two regimes are separated by a very weak décollement and calculate coefficient of friction values that range from 0.25 to 0.08. These values are significantly lower than coefficient of friction values calculated for the basal décollement in the Taiwan fold and thrust belt (e.g., ±0.2 (Barr and Dahlen, 1989a)) and they are also lower than laboratory friction measurements for most rocks (e.g., 0.6–0.8 (Byerlee, 1978)). Consequently, these low values suggest the presence of rocks with unusual material properties (e.g., montmorillonite (Logan and Rauenzahn, 1987)) or anomalous fluid pressures along the décollement. On the basis of the occurrence of shale diapirs, the distribution of early veins, and the absence of montmorillonite in the underthrust sequences, we propose that there was an anomalously high fluid pressure along the décollement fault instead of there being such a low coefficient of friction. These results emphasize the importance of dewatering and fluid flow in controlling the position of the décollement, which in turn determines how the accretionary prism grows. In essence, it is the development of a weak, overpressured décollement within a thick sediment pile that allows plate convergence to be partitioned into offscraping and underthrusting regimes.