Plant Fossilization Processes and Preservation Conditions

Study of Fossils M.Sc-I sem

Some of the many possible fates of plants or their parts as they enter the fossil record.

The study of how organisms or their parts become fossils is called taphonomy. The fate of most organic material produced by living systems is to be decomposed to carbon dioxide and water, and recycled into the biosphere. The circulation of elements through biogeochemical cycles indicates that decomposition is, indeed, efficient; however the presence of organic material in sedimentary rocks (e.g., coal, petroleum, dispersed organic matter, and fossils) shows that some organic matter - or its traces - escapes these cycles to be preserved in the rock record. The study of paleobotany relies on this preserved material - fossils - as evidence of past life. In the early history of modern paleontology, fossils were thought of mostly as static parts of the rock record ("sticks in mud"). Plants become fossilized in a variety of ways. Each type of preservation carries different information about the once-living organism. Thus, an appreciation of plant fossils requires that one understand the processes of fossilization, and how each type of preservation may influence our view of once-living organisms. Plants become fossilized in a variety of ways. Each type of preservation carries different information about the once-living organism. Thus, an appreciation of plant fossils requires that one understand the processes of fossilization, and how each type of preservation may influence our view of once-living organisms.

Conditions Required for Plant Fossil Preservation.:- Three conditions are required for the preservation of plant fossils are: Removing the material from oxygen-rich environment of aerobic decay; "Fixing" the organic material to retard anaerobic decay; Introducing the fossil to the sedimentary rock record (a.k.a., burial).

Types of Plant Fossils Compressions -- 2-dimensional, with organic material Impressions -- imprints, 2-dimensional, devoid of organic matter Casts and Molds -- 3-dimensional, may have a surface layer of organic material Permineralization -- 3-dimensional, tissue infiltrated by minerals allowing internal preservation Compactions -- 3 dimensional, reduced volume, flattened, wholly organic Molecular Fossils -- non-structural, preserves organic compounds

Era Period Epoch EON Phanerozoic Cenozoic Quaternary Recent/Holocene Pleistocene Pliocene Miocene Oligocene Eocene Paleocene Tertiary Mesozoic Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian Vendian Paleozoic Precambrian Proterozoic Archaean Hadean

Flash Card for different Fossils Mold (imprint) fossils When a leaf, feather, bone or even a body of an organism leaves an imprint on sediment, which hardens and becomes rock Cast fossils When minerals fill in the hollows of an animal track, a mollusk shell, or another part of an organism Fossil fuels Fuels formed by the remains of dead plants and animals Actual remains The body of an organism, with all the parts intact. Usually preserved in ice, amber, or tar. Petrified wood When minerals replace wood or stone to create either petrified wood or a mineralized fossil

Compression and Impression

Fossil Cuticle

Impression of leaves with clay film in the Cretaceous Dakota Sandstone

Cast of Quercus acorn.

Permineralised stem of Lepidodendron selaginoides in T.S

Compaction fossil of Halocene Pinus strobes pollen from Asa s Hallow

Coal ball

Petrified forest log : The internal structure of the tree and bark are maintained in the permineralization process.

Sub Fossil----Dodo-Skeleton Natural History Museum London England: Subfossils are often found in depositionary environments, such as lake sediments, oceanic sediments, and soils. Once deposited, physical and chemicalweathering can alter the state of preservation.

An example of a pseudofossil: Manganese dendrites on a limestone bedding plane from Solnhofen, Germany; scale in mm

Three small ammonitefossils, each approximately 1.5 cm across

Petrified cone of Araucaria mirabilis from Patagonia,Argentina dating from theJurassic Period (approx. 210 Ma)

Pennsylvanian coal ball horizons in the Illinois Basin

Miocene amber from Mexico

Jurassic paleosols from the Morrison Formation of Utah.

Carboniferous paleosols from Joggins, Nova Scotia.

Burrowed/backfilled coal of Pennsylvanian age; an example of ichnofossils.

THANKS Dr. Tulika Mishra Deptt of Botany, DDU GU