ALLUVIAL FACIES AND PALEOSOLS IN THE CRETACEOUS NANUSHUK FORMATION, KANAYUT RIVER, NORTH SLOPE, ALASKA: PRELIMINARY RESULTS FROM THE 2001 FIELD SEASON Alluvial facies and paleosols in the Cretaceous Nanushuk Formation, Kanayut River, North Slope, Alaska:

• Main Author: Paul J Mccarthy
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: north slope; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.1073.6931; http://pubs.dggsalaskagov.us/webpubs/dggs/pir/text/pir2003_001.pdf

Abstract Paleosols are increasingly viewed as an important, if not critical component in nonmarine sequence stratigraphic analyses where they mark interfluve sequence boundaries and provide at least qualitative information on relative rates of accommodation change within intervening alluvial strata. However, the application of detailed paleopedological analyses to nonmarine sequence stratigraphic studies is still relatively rare. This study focuses on alluvial and coastal plain deposits of the Cretaceous Nanushuk Formation exposed in outcrop along the Kanayut River south of the NPRA. During the 2001 field season, this site was logged and sampled for subsequent micromorphological, geochemical and mineralogical analyses. Preliminary observations indicate that pedogenic modification of alluvial deposits is common, however, rapid deposition of sediment and generally wet conditions resulted in a preponderance of weakly-developed and poorly-drained paleosols similar to modern Entisols, Inceptisols, Gleysols and Histosols. Sandstone and mudstone paleosols may contain a few large root traces, sometimes expressed as vertical to subhorizontal coalified structures or as surface cradle knolls, but they maintain evidence of primary stratification and cumulic development. Coalified and carbonaceous root traces, organic fragments, blocky structures and abundant siderite nodules provide further evidence of waterlogged conditions. By combining field observations, paleosols micromorphology, geochemistry and mineralogy with regional stratigraphic information, it is possible to pin-point the exact position of sequence boundaries in nonmarine rocks. Further work is planned in an attempt to better understand the regional distribution of paleosols in the Nanushuk Formation in order to better characterize significant nonmarine depositional hiatuses (sequence boundaries) and Cretaceous high latitude paleoenvironmental conditions.