Torres Pérez-Hidalgo, Trinidad José
Features of deep cave sediments: their influence on fossil preservation.
"Estudios geológicos", v. 59
We analyse how physical and chemical deep-cave sediment features preserve the
morphological and geochemical characteristics of paleontological materials. Detrital
sediment chemistry and clast size are fundamental because they provide a soft, impervious
and plastic environment in which fossil remains are transported with minimal erosion.
Sediment mineralogy provides a carbonate- and phosphate-buffered environment in
which molecules of biological origin hydrolyze slower than in open-air environments or
even at cave entrance sites. Because permafrost did not develop in the Iberian Peninsula
(at least at the altitudes of inhabited caves), sediment desiccation never took place. In
addition, sediment -pores were not aerated, which protected fossil remains from air
(oxygen)-linked weathering. The annual-temperature variation inside sediment was
negligible, which contributed to amino acid racemization dating. Collagen amino acid
and amino acid racemization analysis of cave bear and man samples from cave sediments
dated from different Oxygen Isotope Stages (4th: Sidrón, Amutxate, Troskaeta, El
Toll, Coro Tracito, Ekain, Lezetxiki, La Pasada, Eirós; 5th : Reguerillo and Arrikrutz;
6th_7th : Sima de los Huesos) demonstrate that important amounts of almost intact collagen
still remain in teeth dentine. Fossil DNA search seems to be very promising.