User:Jdayala/Taphonomy

Research areas[edit]

Actualistic taphonomy seeks to understand taphonomic processes through experimentation, such as the burial of bone.^[8] Taphonomy has undergone an explosion of interest since the 1980s,^[9] with research focusing on certain areas.

• Microbial, biogeochemical, and larger-scale controls on the preservation of different tissue types; in particular, exceptional preservation in Konzervat-lagerstätten. Covered within this field is the dominance of biological versus physical agents in the destruction of remains from all major taxonomic groups (plants, invertebrates, vertebrates).
• Processes that concentrate biological remains; especially the degree to which different types of assemblages reflect the species composition and abundance of source faunas and floras.
• Actualistic taphonomy uses the present to understand past taphonomic events. This is often done through controlled experiments,^[10] such as the role microbes play in fossilization,^[11] the effects of mammalian carnivores on bone,^[12] or the burial of bone in a water flume.^[8] Computer modeling is also used to explain taphonomic events.^[8][13]
• The spatio-temporal resolution^{[clarification needed]} and ecological fidelity^{[clarification needed]} of species assemblages, particularly the relatively minor role of out-of-habitat transport contrasted with the major effects of time-averaging.^{[clarification needed]}
• The outlines of megabiases in the fossil record, including the evolution of new bauplans and behavioral capabilities, and by broad-scale changes in climate, tectonics, and geochemistry of Earth surface systems.
• The Mars Science Laboratory mission objectives evolved from assessment of ancient Mars habitability to developing predictive models on taphonomy.^{[clarification needed][14]}

Paleontology[edit]

One motivation behind taphonomy is to understand biases present in the fossil record better. Fossils are ubiquitous in sedimentary rocks, yet paleontologists cannot draw the most accurate conclusions about the lives and ecology of the fossilized organisms without knowing about the processes involved in their fossilization. For example, if a fossil assemblage contains more of one type of fossil than another, one can infer either that the organism was present in greater numbers, or that its remains were more resistant to decomposition.

During the late twentieth century, taphonomic data began to be applied to other paleontological subfields such as paleobiology, paleoceanography, ichnology (the study of trace fossils) and biostratigraphy. By coming to understand the oceanographic and ethological implications of observed taphonomic patterns, paleontologists have been able to provide new and meaningful interpretations and correlations that would have otherwise remained obscure in the fossil record.

Forensic science[edit]

Forensic taphonomy is a relatively new field that has increased in popularity in the past 15 years. It is a subfield of forensic anthropology focusing specifically on how taphonomic forces have altered criminal evidence.^[15]

There are two different branches of forensic taphonomy: biotaphonomy and geotaphonomy. Biotaphonomy looks at how the decomposition and/or destruction of the organism has happened. The main factors that affect this branch are categorized into three groups: environmental factors; external variables, individual factors; factors from the organism itself (i.e. body size, age, etc.), and cultural factors; factors specific to any cultural behaviors that would affect the decomposition (burial practices). Geotaphonomy studies how the burial practices and the burial itself affects the surrounding environment. This includes soil disturbances and tool marks from digging the grave, disruption of plant growth and soil pH from the decomposing body, and the alteration of the land and water drainage from introducing an unnatural mass to the area.^[16]

This field is extremely important because it helps scientists use the taphonomic profile to help determine what happened to the remains at the time of death (perimortem) and after death (postmortem). This can make a huge difference when considering what can be used as evidence in a criminal investigation.^[17]

Environmental archaeology[edit]

Archaeologists study taphonomic processes in order to determine how plant and animal (including human) remains accumulate and differentially preserve within archaeological sites. Environmental archaeology is a multidisciplinary field of study that focuses on understanding the past relationships between groups and their environments. The main subfields of environmental archaeology include zooarchaeology, paleobotany, and geoarchaeology. Taphonomy allows specialists to identify what artifacts or remains encountered before and after initial burial. Zooarchaeology, a focus within environmental archaeology investigates taphonomic processes on animal remains. The processes most commonly identified within zooarchaeology include thermal alteration (burns), cut marks, worked bone, and gnaw marks.^[18] Thermally altered bone indicate the use of fire and animal processing. Cut marks and worked bone can inform zooarchaeologists on tool use or food processing.^[19] When there is little to no written record, taphonomy allows environmental archaeologists to better comprehend the ways in which a group interacted with their surrounding environments and inhabitants.

The field of environmental archaeology provides crucial information for attempting to understand the resilience of past societies and the great impacts that environmental shifts can have on a population. Knowledge gained from the past through these studies can be used to inform present and future decisions for human-environment interactions.

Microbial Mats

Modern experiments have been conducted on post-mortem invertebrates and vertebrates to understand how microbial mats and microbial activity influence the formation of fossils and the preservation of soft tissues. In these studies, microbial mats entomb animal carcasses in a sarcophagus of microbes—the sarcophagus entombing the animal's carcass delays decay. Entombed carcasses were observed to be more intact than non-entombed counter-parts by years at a time. Microbial mats maintained and stabilized  the articulation of the joints and the skeleton of post-mortem organisms, as seen in frog carcasses for up to 1080 days after coverage by the mats. The environment within the entombed carcasses is typically described as anoxic and acidic during the initial stage of decomposition. These conditions are perpetuated by the exhaustion of oxygen by aerobic bacteria within the carcass creating an environment ideal for the preservation of soft tissues, such as muscle tissue and brain tissue. The anoxic and acidic conditions created by that mats also inhibit the process of autolysis within the carcasses delaying decay even further.  Endogenous gut bacteria have also been described to aid the preservation of invertebrate soft tissue by delaying decay and stabilizing soft tissue structures. Gut bacteria form pseudomorphs replicating the form of soft tissues within the animal. These pseudomorphs are possible explanation for the increased occurrence of preserved guts impression among invertebrates [33]. In the later stages of the prolonged decomposition of the carcasses, the environment within the sarcophagus alters to more oxic and basic conditions promoting biomineralization and the precipitation of calcium carbonate.

Microbial mats additionally play a role in the formation of molds and impressions of carcasses. These molds and impressions replicate and preserve the integument of animal carcasses. The degree to which has been demonstrated in frog skin preservation. The original morphology of the frog skin, including structures such as warts, was preserved for more than 1.5 years. The microbial mats also aided in the formation of the mineral gypsum embedded within the frog skin. The microbes that constitute the microbial mats in addition to forming a sarcophagus, secrete an exopolymeric substances (EPS) that drive biomineralization. The EPS provides a nucleated center for biomineralization. During later stages of decomposition heterotrophic microbes degrade the EPS, facilitating the release of calcium ions into the environment and creating a Ca-enriched film. The degradation of the EPS and formation of the Ca-rich film is suggested to aid in the precipitation of calcium carbonate and further the process of biomineralization .

References

31. Iniesto, Miguel & Villalba, I & Delgado Buscalioni, Angela & Guerrero, M.C. & López-Archilla, Ana. (2017). The Effect Of Microbial Mats In The Decay Of Anurans With Implications For Understanding Taphonomic Processes In The Fossil Record. Scientific Reports. 7. 45160. 10.1038/srep45160.

32. Iniesto, M., Buscalioni, Á., Carmen Guerrero, M. et al. Involvement of microbial mats in early fossilization by decay delay and formation of impressions and replicas of vertebrates and invertebrates. Sci Rep 6, 25716 (2016). https://doi.org/10.1038/srep25716

33. Butler Aodhán D., Cunningham John A., Budd Graham E. and Donoghue Philip C. J.

2015. Experimental taphonomy of Artemia reveals the role of endogenous microbes in mediating decay and fossilizationProc. R. Soc. B.2822015047620150476

http://doi.org/10.1098/rspb.2015.0476

33.4 INIESTO, M., LAGUNA, C., FLORIN, M., GUERRERO, M. C., CHICOTE, A., BUSCALIONI, A. D., & LÓPEZ-ARCHILLA, A. I. (2015). THE IMPACT OF MICROBIAL MATS AND THEIR MICROENVIRONMENTAL CONDITIONS IN EARLY DECAY OF FISH. PALAIOS, 30(11/12), 792–801. http://www.jstor.org/stable/44708731

Role of Microbial mats