Pseudofossils are
inorganic
In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemist ...
objects, markings, or impressions that might be mistaken for
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s. Pseudofossils may be misleading, as some types of mineral deposits can mimic lifeforms by forming what appear to be highly detailed or organized structures. One common example is when
manganese
Manganese is a chemical element with the Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese is a transition metal with a multifaceted array of ...
oxides
crystallize
Crystallization is the process by which solid forms, where the atoms or molecules are highly organized into a structure known as a crystal. Some ways by which crystals form are precipitating from a solution, freezing, or more rarely deposi ...
with a characteristic treelike or
dendritic
Dendrite derives from the Greek word "dendron" meaning ( "tree-like"), and may refer to:
Biology
*Dendrite, a branched projection of a neuron
* Dendrite (non-neuronal), branching projections of certain skin cells and immune cells
Physical
*Dendr ...
pattern along a rock fracture. The formation of
frost
Frost is a thin layer of ice on a solid surface, which forms from water vapor in an above-freezing atmosphere coming in contact with a solid surface whose temperature is below freezing, and resulting in a phase change from water vapor (a g ...
dendrites on a window is another common example of this crystal growth.
Concretion
A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular ...
s are sometimes thought to be fossils, and occasionally one contains a fossil, but are generally not fossils themselves.
Chert
Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a ...
or
flint
Flint, occasionally flintstone, is a sedimentary cryptocrystalline form of the mineral quartz, categorized as the variety of chert that occurs in chalk or marly limestone. Flint was widely used historically to make stone tools and start ...
nodules in
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...
can often take forms that resemble fossils.
Background
Pyrite
The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic Luster (mineralogy), lust ...
disks or spindles are sometimes mistaken for fossils of
sand dollars or other forms (see
marcasite). Cracks, bumps,
gas bubbles, and such can be difficult to distinguish from true fossils. Specimens that cannot be attributed with certainty to either fossils or pseudofossils are treated as
dubiofossil
{{More citations needed, date=October 2021
The term dubiofossil is a portmanteau word used in geology and paleontology for a problematic structure that looks like a fossil but has an uncertain biologic origin. From Latin ''dubius'', and English fo ...
s. Debates on whether specific forms are pseudo or true fossils can be lengthy and difficult. For example, ''
Eozoön'' is a complex laminated form of interlayered
calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scratc ...
and
serpentine originally found in
Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...
metamorphosed
limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms w ...
s (marbles). It was at first thought to be the remains of a giant fossil protozoan (Dawson, 1865), then by far the oldest fossil known. Similar structures were subsequently found in metamorphosed
limestone blocks ejected during an eruption of
Mount Vesuvius
Mount Vesuvius ( ; it, Vesuvio ; nap, 'O Vesuvio , also or ; la, Vesuvius , also , or ) is a somma-stratovolcano located on the Gulf of Naples in Campania, Italy, about east of Naples and a short distance from the shore. It is one of ...
. It was clear that high-temperature physical and chemical processes were responsible for the formation of ''Eozoön'' in the carbonate rock (O'Brien, 1970). The debate over the interpretation of ''Eozoon'' was a significant episode in the history of paleontology (Adelman, 2007).
Chemical gardens
Comparison of chemical gardens grown by NASA scientists on the International Space Station (left) and on the ground (right)
A chemical garden while growing
up Cobalt(II) chloride
upA chemical garden
A chemical garden is a set of complex biol ...
can produce branching microtubuli of 2-10 μm in diameter and can resemble very closely the shapes of
fossilized primitive
fungi
A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...
or
microorganisms
A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
. It has been proposed that ancient,
precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...
, structures that have been identified as the evidence for the first fungi or even the first life, are more probably products of ancient natural chemical gardens.
Image:Dendrites01.jpg, Manganese Dendrite (crystal)
A crystal dendrite is a crystal that develops with a typical multi-branching form. The name comes from the Greek word dendron (δενδρον) which means "tree", since the crystal's structure resembles that of a tree. These crystals can be syn ...
on a limestone bedding plane from Solnhofen
Solnhofen is a municipality in the district of Weißenburg-Gunzenhausen in the region of Middle Franconia in the ' of Bavaria in Germany. It is in the Altmühl valley.
The local area is famous in geology and palaeontology for Solnhofen limes ...
, Germany. Scale in mm.
Image:Concretion01.jpg, Concretion
A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular ...
with calcite-filled septarian cracks. Scale in mm.
Image:Eozoon01.jpg, ''Eozoön canadense'' from the Precambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...
of Canada, a metamorphic rock made of interlayered calcite and serpentine. A well-known pseudofossil (Adelman, 2007). Scale in mm.
Image:ShatterCones.jpg, Cone-in-cone structures produced by compression of limestone. Sometimes mistaken for fossils, thus becoming examples of pseudofossils.
Image:Markasit hg.jpg, A marcasite crystal form resembling a sand dollar.
Image:Pseudocoprolite.jpg, A Miocene
The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
pseudocoprolite from Washington state. This is one of the most common pseudofossils because it so closely resembles a coprolite
A coprolite (also known as a coprolith) is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. The name is ...
. Scale in mm. See Spencer (1993).
Image:ConcretionPseudofossil.jpg, Cross-section of a concretion showing layers that resemble tree rings.
References
Bibliography
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{{Commons category, Pseudofossils
Pseudofossils