[Administrator: this is being separated from the "Varve" thread as it is heading in a new direction.] DAVID PLAISTED Here are some references on fossilization. Can someone point me to references stating that fossilization can occur without the organism rapidly being buried? All of these references seem to imply rapid burial. --------- Mechanisms of fossilization of the soft-bodied and lightly armored faunas of the Burgess Shale and of some other classical localities Petrovich R AMERICAN JOURNAL OF SCIENCE 301 (8): 683-726 OCT 2001 Abstract: The splendid preservation of the Middle Cambrian Burgess Shale fauna, a fauna of exceptional importance for our understanding of the evolution of life, has not been adequately explained. Preservation of diagenetically altered remnants of the original organic tissues and formation of chlorite/illite coatings and cuticle replacements, both documented in the Burgess Shale fossils though not necessarily occurring together, can be understood as products of the same mechanism of fossilization of soft tissues. It is argued here that this mechanism consists of the following steps:1) adsorption on structural biopolymers such as chitin, cellulose, and collagens of Fe2+ ions released during the oxidation of organic matter by iron(Ill)reducing bacteria, (2) inhibition by the adsorbed Fe2+ ions of further bacterial decomposition of these biopolymers, which enables them to persist and later become kerogens; (3) in some microenvironments, nucleation of crystals of an iron(II)-rich clay mineral, a berthierine or a ferroan saponite, on the Fe2+ ions adsorbed on the preserved biopolymers and growth of such clay-mineral crystals to form a coating on the organic remains and/or to replace parts of the organism. The critical factors in the Burgess Shale-type preservation of Early and Middle Cambrian soft-bodied and lightly armored animals were probably: (1) rapid transport of live or freshly killed organisms into suboxic water, (2) extensive suboxic diagenesis in a sediment of high iron(III)/ (organic carbon) ratio, and (3) curtailment of the supply of sulfate ions shortly after the onset of pyritization. The proposed model of early diagenesis that results in Burgess Shale-type fossil preservation critically depends on the availability of steady suboxic depositional environments in open oceanic settings at depths of the order of 100 m in which iron(HI)-rich fine-grained sediments, rapidly deposited with the entrained animals by turbidity currents, could accumulate without being disturbed by storm waves and deep currents. Evidence discussed in the present paper suggests that such conditions were common in the Early and Middle Cambrian. --------- Enhancement of leaf fossilization potential by bacterial biofilms Dunn KA, McLean RJC, Upchurch GR, Folk RL GEOLOGY 25 (12): 1119-1122 DEC 1997 Abstract: Terrestrial leaf fossils often form through authigenic preservation in which the leaf surface is coated by a variety of minerals, especially iron oxides. The mechanism of this fossilization is unclear, because the largely hydrophobic leaf surfaces do not readily bind metal ions. Previously proposed mechanisms for mineral encrustation include precipitation of minerals in sediment pore space and precipitation of iron oxides at the surface by decay-produced CO2. Here we demonstrate that diverse bacterial species rapidly colonize leaf surfaces and form a biofilm within days of the leaf's entry into a stream environment. Experimental mineralization of fresh and biofilm-coated leaves indicates that leaves without biofilm do not mineralize, but leaves with biofilms rapidly adsorb metal ions such as Fe3+ onto the anionic biofilm surface where the ions form ferrihydrite. Once these mineralized leaves are buried by the sediment, they are more likely to be converted to fossils than nonmineralized leaves. Examination of a fossil leaf surface by scanning electron microscopy shows bacteria-sized structures resembling those found in biofilms, These experimental data imply that bacterial colonization of leaves may be an essential prerequisite for authigenic preservation. --------- FOSSILIZATION OF SOFT-TISSUE IN THE LABORATORY BRIGGS DEG, KEAR AJ SCIENCE 259 (5100): 1439-1442 MAR 5 1993 Abstract: Some of the most remarkable fossils preserve cellular details of soft tissues. In many of these, the tissues have been replaced by calcium phosphate. This process has been assumed to require elevated concentrations of phosphate in sediment pore waters. In decay experiments modern shrimps became partially mineralized in amorphous calcium phosphate, preserving cellular details of muscle tissue, particularly in a system closed to oxygen. The source for the formation of calcium phosphate was the shrimp itself. Mineralization, which was accompanied by a drop in pH, commenced within 2 weeks and increased in extent for at least 4 to 8 weeks. This mechanism halts the normal loss of detail of soft-tissue morphology before fossilization. Similar closed conditions would prevail where organisms are rapidly overgrown by microbial mats.