Why are they still there? A model of accumulation and decay of organic prehistoric cultural deposits. (September 2015)

• Record Type: Journal Article
• Authors: Bleicher, Niels; Schubert, Carsten
• Is Part Of: Journal of archaeological science. Volume 61(2015:Sep.)
• Page Start: 277
• Page End: 286
• Publication Date: 2015-09
• Subjects: Organic preservation -- Wetland archaeology -- Degradation -- Decay model -- Lake side settlements -- Organische kulturschichten -- Fumier lacustre; Archaeology -- Periodicals; Archéologie -- Périodiques; 930.1
• DOI: 10.1016/j.jas.2015.06.010
• Languages: English
• ISSNs: 0305-4403

Abstract

Abstract: The circumalpine lake side settlements are a unique source of detailed information on the past. Nevertheless, little has been published by now on why the organic matter (fumier lacustre) in these settlements has been preserved and how exactly this happened. It is, therefore, necessary to closely explore the decomposition of organic matter under different conditions. We present data from the literature and a decomposition model simulating the outcome of different archaeological hypotheses and comparing the result with the actual archaeological record. We conclude that different scenarios of deposition should result in clearly discernible and measurable features in the archaeological record, whose presence or absence allows deducing the mode of deposition. The best conditions of organic preservation are to be expected under such conditions where a large organic input happens in shallow still water. Seasonal flooding and a later rise in lake level can also result in good preservation but imply a greater loss through mechanical erosion and in many cases clear preservation gradients within the deposits. The theoretical outcomes presented here find clear analogs in the archaeological record. Highlights: Using results from research on organic decay, a model of organic preservation in waterlogged sites is presented. Interpretations that postulate waterlogged conditions as a consequence of subsequent lake level changes are highly unlikely. The model predicts the best agreement with actual archaeological records in a scenario with deposition in shallow water. Quick deposition of large amounts of organic material causes organic preservation with early decay depleting Oxygen. The mechanisms of organic preservation in bog settlements are different from those in lake.