DOI: 10.1016/j.palaeo.2017.06.030
论文题名: Bioerosion of a modern bedrock stream bed by insect larvae (Conecuh River, Alabama): Implications for ichnotaxonomy, continental ichnofacies, and biogeomorphology
作者: Savrda C.E.
刊名: Palaeogeography, Palaeoclimatology, Palaeoecology
ISSN: 0031-0182
出版年: 2017
语种: 英语
英文关键词: Chironomid larvae
; Firmground
; Glossifungites ichnofacies
; Ichnology
; Trichopteran larvae
英文摘要: Observations along the Conecuh River, southern Alabama, demonstrate the impact that insect larvae can have on bioerosion of freshwater aquatic bedrock substrates. Eocene siliceous claystones and sandstones exposed along the river are locally densely riddled by modern burrows produced by chironomid (midge) and trichopteran (caddisfly) larvae. Chironomid larvae produce diminutive U-shaped burrows (U width = 2-7. mm, U length = 1-4. cm, burrow diameter = 0.5-2.0. mm) generally oriented normal to bedrock surfaces. Trichopteran larvae generally produce somewhat larger (burrow depth = 2-4. cm, burrow diameter = 4-6. mm), vertical, crudely Y-shaped burrows consisting of an upper U-tube, which is extended above the substrate by agglutinated chimneys, and one or two basal subvertical shafts. Both burrow types exhibit faint scratch traces on exposed burrow margins and silk-and-sediment linings that include a thicker constructed wall or septum in interlimb areas of their U-tubes. Distribution of the two structure types is controlled by bedrock texture and induration, tracemaker propensity to occupy transiently available substrates, and other as yet unidentified factors.Chironomid and trichopteran larvae burrows in these firmgrounds resemble the ichnotaxa Arenicolites and Polykladichnus, respectively. However, differences in burrow production in soft versus firm substrates, combined with uncertainties with regard to potential modes of preservation of the modern burrows, make it difficult to establish ichnotaxonomic equivalence and raise broader questions regarding inferred behavior and ichnotaxonomy of U-form burrows in firmgrounds (e.g., Rhizocorallium). Regardless of ichnotaxonomic assignment, ichnofabrics produced by modern insect larvae in fluvial firmgrounds closely match those diagnostic of the Glossifungites ichnofacies in marine and marginal strata, and thus the scope of this ichnofacies arguably should be expanded to include comparable ichnofossil assemblages preserved in ancient continental deposits. Beyond their implications for palichnology, observations made herein underscore the need to include bedrock stream channels and their biota in integrative biogeomorphologic investigations. © 2017. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/68089
Appears in Collections: 过去全球变化的重建
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作者单位: Department of Geosciences, 2050 Beard-Eaves Coliseum, Auburn University, AL 36849, USA
Recommended Citation:
Savrda C.E.. Bioerosion of a modern bedrock stream bed by insect larvae (Conecuh River, Alabama): Implications for ichnotaxonomy, continental ichnofacies, and biogeomorphology[J]. Palaeogeography, Palaeoclimatology, Palaeoecology,2017-01-01