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Sometimes, fossils contain only carbon. Fossils usually form when sediment buries a dead organism. As sediment piles up, the organism's remains are subjected to pressure and heat. These conditions force gases and liquids from the body. A thin film of carbon residue is left, forming a silhouette of the original organism called a carbon film. [1]
A transitional fossil is any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group. [1] This is especially important where the descendant group is sharply differentiated by gross anatomy and mode of living from the ancestral group.
The origin of fossil fuels is the anaerobic decomposition of buried dead organisms. The conversion from these organic materials to high-carbon fossil fuels typically requires a geological process of millions of years. [4] Due to the length of time it takes for them to form, fossil fuels are considered non-renewable resources.
Evidence of possibly the oldest forms of life on Earth has been found in hydrothermal vent precipitates. [1]The earliest known life forms on Earth may be as old as 4.1 billion years (or Ga) according to biologically fractionated graphite inside a single zircon grain in the Jack Hills range of Australia. [2]
Fossilized stromatolites exhibit a variety of forms and structures, or morphologies, including conical, stratiform, domal, columnar, [13] and branching types. [14] Stromatolites occur widely in the fossil record of the Precambrian but are rare today. [15]
Tree remains that have undergone petrifaction, as seen in Petrified Forest National Park. In geology, petrifaction or petrification (from Ancient Greek πέτρα (pétra) ' rock, stone ') is the process by which organic material becomes a fossil through the replacement of the original material and the filling of the original pore spaces with minerals.
Sedimentary rocks are formed through the gradual accumulation of sediments: for example, sand on a beach or mud on a river bed. As the sediments are buried they get compacted as more and more material is deposited on top. Eventually the sediments will become so dense that they would essentially form a rock. This process is known as lithification.
The fossil record and faunal succession form the basis of the science of biostratigraphy or determining the age of rocks based on embedded fossils. For the first 150 years of geology , biostratigraphy and superposition were the only means for determining the relative age of rocks.