科研之友
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摘要
The Conemaugh Group of southeastern Ohio contains numerous ichnofossil-bearing paleosols in both the lower Glenshaw and upper Casselman formations, which were deposited during the Kasimovian and Gzhelian (305-301 Ma) along the distal edge of the Appalachian basin. This study examined the small-scale (<1 km) lateral variability in some of these paleosols and the role of organisms in the soil-forming processes during the Late Pennsylvanian.
Twenty four stratigraphic sections were measured from ten sites in Athens County, Ohio from which thirty paleosols were identified and described. Detailed field descriptions allowed differentiation of four distinct pedotypes; one in the Glenshaw Formation and three in the Casselman Formation. The Glenshaw Pedotype (GPT) is a Vertisol that formed on a proximal to distal floodplain. The three Casselman pedotypes represent Entisols/Inceptisols (CPTI) Alfisols (CPTII) and Vertisols (CPTIII). All four types contain evidence of alteration by post-pedogenic processes such as 'drowning' by migrating river channels or rising sea level or a gradual transition from one alluvial subenvironment to another as a result of channel migration.
Eight morphologically distinct ichnofossils were observed in the Conemaugh Group paleosols including three types of rhizoliths, lined and unlined, vertical to subhorizontal shafts, chambers, sinuous burrows with and without bioglyphs, and general burrow mottling. These ichnofossils occur in distinct assemblages that form unique ichnocoenoses within each of the four pedotypes. They were produced by various plants, arthropod detritivores, carnivores, and herbivores as well as amphibians and early reptiles as temporary to permanent members of complex soil ecosystems.
Pedogenic properties combined with ichnofossil diversity, abundance, and distribution increase the understanding of the complexity of Late Pennsylvanian soil ecosystems and provide details on the small-scale variations in paleosols due to short-term autogenic changes in alluvial environments. Although broad, regional studies across 10(2)-10(3) of kilometers are important, small scale variations over less than 1 km are needed to understand the effects of localized changes in hydrology, topography, organisms, and sedimentary processes on soil formation and soil biodiversity. Consideration of these types of localized studies is also vital when attempting to interpret regional to global-scale aspects of environment such as climate from paleosols.
- 出版日期2011-12-1
