Learning Objective 2.1
Define Taphonomy
the study of all natural processes that involved an organism after it dies
- includes: decay, how they are scavenged, fossilized and eroded
Learning Objective 2.1
Explain the phenomeon of bloat-and-float
after decay, body might swell with putrid gasses, and this may cause the carcasses of animals to float easily and to be transported by shallow and weakly flowing water
Learning Objective 2.1
what are the 6 taphonomic factors that can contribute to the disarticulation of a skeleton?
- partial consumped by carnivores
- carcasses may be easily broken apart if dwept away by rivers or flood waters - water currents may also carry different portions of a skeleton to different locations
- prolonged exposure to sunlight gradually weakens and disintegrates bone
- skeletons can be partially buried = eventually lose their exposed portions
- portions can also be trampled by animals
- portions have their mineral content leached away by the roots of plants
Learning Objective 2.1
Define plastic deformation
occurs when pressure casues the shape of a buried fossil to be changed such that even the pressure
Learning Objective 2.2
what are the 2 best environmental factors for fossilization
- wet environments; water could help wash sand or mud over carcass
- lower elevations; sand and mud carried in by water are able to build up (compared to higher elevations where sand and mude are often carried away by erosion)
Learning Objective 2.2
Where do we often find dinosaur skeletons?
define fluvial deposits
in ancient river, stream, and lake deposits
- fluvial deposits: river and stream deposits
Learning Objective 2.2
define lacustrine deposits
died and preserved in lakes
- have a better chance of persercing soft tissues like hair or feathers in the fossil
- little water movement to disrupt the skeleton
- sediments laid down in lakes are very fine-grained (it’s easier to preserve impressions of feathers in mud than in sand)
Learning Objective 2.3
Define sedimentary, igneous and metamorphic
- sedimentary: rocks that form when mineral and organic particles accumulate and become either cemented or compacted together
- igneous: form when magma or laval cools
- metamorphic: form when sedimentary or igneous roks are changed by heat or pressure
Learning Objective 2.3
define sedimentology
the science of how sedimentary rocks form
Learning Objective 2.3
what is mudstone and shale and what environment did it indicate?
- sedimentary rocks that form from mud and silt (accumulation of large amounts of mud and silt)
- indicate a former lake bottom environment
Learning Objective 2.3
what is sandstone and what does it indicate
- sedimentary rocks that form from sand
- indicate a former beach environment, river channel or ocean floor environment
Learning Objective 2.3
what is limestone and what does it indicate
- formed from the accumulation of shells and exoskeletons of small marine invertebrates
- indicate a former shallow marine environment
Learning Objective 2.4
define preservation styles
describe the 2 types
the different ways that fossils form
1. permineralization: occurs when the empty internal spaces fo a bone are filled with minerals ; done when minerals are first dissolved in water and are then deposited in the empty bone spaces as water soaks through the bone
2. replacement: occurs when the original bone gradually decays and minerals fill the space that the bone once occupied
Learning Objective 2.5
what is one of the best places to hunt for fossils?
- the Badlands
- area where vegetation is sparse, where erosion rates are high, and where the expanses of ancient sedimentary rocks are exposed
Learning Objective 2.5
what is the ideal dinosaur skeleton?
- one that is freshly and only just barely exposed above ground
Learning Objective 2.5
what is the first step in excavation?
define: overburden
- overburden removal
-overburden: rock and earth taht covers a fossil specimen and that must be removed before the full extent of the specimen can be judged
Learning Objective 2.5
what are the steps in collecting dinosaur bones?
- removing overburden
- map the relative positions of the bone bed
- protect the fossil bone for transportation; done with a protective later of material (cloth, paper towel, or aluminum foil) then covered in burlap that have been soaked in plaster
- speical glues are applied to the fossils
- final work takes place in the lab and this process often takes more time than field excavation
Learning Objective 2.6
what are the 4 clues that could help a palaeontologist understand what happened to a dinosaur after it died?
- disarticulation of a skeleton; due to specimen being trasported by water or carnivores eating the carcass
- orientation: long bones aligned in the same direction indicate that the bones were transported by water and tell us the direction the water was flowing
- abrasion: amount of abrasion on the bones can give a realtive sense for how far the bones may have been transpoerted by flowing water
- tooth marks; scratches on bones indicating that carnivores fed on carcasses
