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Questions and Answers
Shells in a concave-down orientation typically indicate wave or ______ activity that was strong enough to flip them, but too weak to consistently orient them horizontally.
Shells in a concave-down orientation typically indicate wave or ______ activity that was strong enough to flip them, but too weak to consistently orient them horizontally.
current
A strong bimodal orientation of shells, with apices pointing in two directions 180 degrees apart, suggests ______ wave action.
A strong bimodal orientation of shells, with apices pointing in two directions 180 degrees apart, suggests ______ wave action.
strong
Shells that are described as ______ are found in the same environment they lived in, or have been slightly shuffled around, retaining close ties to the original living community.
Shells that are described as ______ are found in the same environment they lived in, or have been slightly shuffled around, retaining close ties to the original living community.
indigenous
[Blank] shells are those that have been transported from a different environment but are from the same geological time; these are often deposited by storms.
[Blank] shells are those that have been transported from a different environment but are from the same geological time; these are often deposited by storms.
Reworked (or remanie) shells are ______ from older rocks that have been mixed with newer sediments, which can potentially mislead age dating if not recognized.
Reworked (or remanie) shells are ______ from older rocks that have been mixed with newer sediments, which can potentially mislead age dating if not recognized.
[Blank] is the study of fossilized organisms, their life, and their environment.
[Blank] is the study of fossilized organisms, their life, and their environment.
Taphonomy examines the changes that occur to an organism from its ______ to its eventual discovery as a fossil.
Taphonomy examines the changes that occur to an organism from its ______ to its eventual discovery as a fossil.
The hierarchical classification of life includes: Domain, Kingdom, Phylum, ______, Class, Order, and Family.
The hierarchical classification of life includes: Domain, Kingdom, Phylum, ______, Class, Order, and Family.
During recrystallization, there's a change in the crystal ______, but the chemical composition remains the same.
During recrystallization, there's a change in the crystal ______, but the chemical composition remains the same.
[Blank] occurs when heat and pressure remove volatile elements from a substance, leaving behind a carbon film.
[Blank] occurs when heat and pressure remove volatile elements from a substance, leaving behind a carbon film.
Fossils can be physical remains like bones, mineral replacements, biological impressions, or even ______ signatures indicating life.
Fossils can be physical remains like bones, mineral replacements, biological impressions, or even ______ signatures indicating life.
The process of turning organic material into stone by infilling with minerals is known as ______ or petrification.
The process of turning organic material into stone by infilling with minerals is known as ______ or petrification.
Fossil ______ like the Burgess Shale are known for the exceptional preservation of soft tissues and articulated hard parts.
Fossil ______ like the Burgess Shale are known for the exceptional preservation of soft tissues and articulated hard parts.
In replacement, the original skeleton dissolves, and a new ______ precipitates in its place, altering the fossil's composition.
In replacement, the original skeleton dissolves, and a new ______ precipitates in its place, altering the fossil's composition.
[Blank] soft part preservation involves no change to organic tissues except for water loss, and can occur due to freezing or mummification.
[Blank] soft part preservation involves no change to organic tissues except for water loss, and can occur due to freezing or mummification.
Leached fossils, commonly found in molluscs with aragonite shells, result from the original shell ______, leaving a void.
Leached fossils, commonly found in molluscs with aragonite shells, result from the original shell ______, leaving a void.
The process of rapid burial, also known as ______, creates conditions favorable for the preservation of both soft and hard tissues by quickly removing the potential for their decomposition.
The process of rapid burial, also known as ______, creates conditions favorable for the preservation of both soft and hard tissues by quickly removing the potential for their decomposition.
Organisms with hard parts made of ______, like molluscs and modern corals, are prone to dissolution, especially in low-pH environments.
Organisms with hard parts made of ______, like molluscs and modern corals, are prone to dissolution, especially in low-pH environments.
A steinkern, a type of fossil mold, preserves internal features of the organism, like ______ attachments.
A steinkern, a type of fossil mold, preserves internal features of the organism, like ______ attachments.
A cast fossil provides a full replica of the original organism, preserving both internal and ______ features.
A cast fossil provides a full replica of the original organism, preserving both internal and ______ features.
[Blank], a type of biogenic structures, refers to the layering and stratification caused by living organisms in sedimentary deposits.
[Blank], a type of biogenic structures, refers to the layering and stratification caused by living organisms in sedimentary deposits.
The high areas of stromatolites grow faster than low areas which leads to ______ increasing upward to form the stromatolite structure.
The high areas of stromatolites grow faster than low areas which leads to ______ increasing upward to form the stromatolite structure.
______ are chemical compounds found in the cell walls of bacteria and can be used as biomarkers.
______ are chemical compounds found in the cell walls of bacteria and can be used as biomarkers.
The preservation of complete arthropods and echinoderms requires rapid ______ to prevent disarticulation and scattering of their components.
The preservation of complete arthropods and echinoderms requires rapid ______ to prevent disarticulation and scattering of their components.
______ is the term for the progressive disintegration of crinoids after death, resulting in a range of fossil forms from complete calyces to disarticulated columnals.
______ is the term for the progressive disintegration of crinoids after death, resulting in a range of fossil forms from complete calyces to disarticulated columnals.
Fossil ______ is the term used to describe the accumulation of broken and fragmented shells due to extensive abrasion and transport.
Fossil ______ is the term used to describe the accumulation of broken and fragmented shells due to extensive abrasion and transport.
According to the Mohs Hardness Scale, ______, with a hardness of 7, is harder than calcite, which has a hardness of 3.
According to the Mohs Hardness Scale, ______, with a hardness of 7, is harder than calcite, which has a hardness of 3.
The transport of shells in ______ currents, where the shells move along the seabed, typically results in extensive abrasion due to frequent contact with other particles.
The transport of shells in ______ currents, where the shells move along the seabed, typically results in extensive abrasion due to frequent contact with other particles.
______ orientation of shells occurs when currents or waves align them, with their apices pointing in the same direction, indicating the direction of flow.
______ orientation of shells occurs when currents or waves align them, with their apices pointing in the same direction, indicating the direction of flow.
Flashcards
Shell Orientation: Unidirectional Current
Shell Orientation: Unidirectional Current
Current flows in one direction, but direction is unidentifiable from shell orientation alone.
Shell Orientation: Bimodal
Shell Orientation: Bimodal
Shell apices point in two opposing directions (180° apart), suggesting an oscillating current.
Shell Orientation: Concave-down
Shell Orientation: Concave-down
Shell orientation where concave-down indicates wave or current activity strong enough to flip shells, but not strongly orient them.
Shell Dissolution
Shell Dissolution
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Indigenous Shells
Indigenous Shells
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Classification Hierarchy
Classification Hierarchy
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Taphonomy
Taphonomy
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Paleoecology
Paleoecology
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Fossil
Fossil
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Unaltered Soft Parts
Unaltered Soft Parts
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Altered Soft Parts
Altered Soft Parts
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Fossil Lagerstatten
Fossil Lagerstatten
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Unaltered Hard Parts
Unaltered Hard Parts
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Fossil Substance
Fossil Substance
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Recrystallization
Recrystallization
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Carbonization
Carbonization
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Permineralization
Permineralization
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Replacement (Fossil)
Replacement (Fossil)
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Leached Fossil
Leached Fossil
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Steinkern (Core)
Steinkern (Core)
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Cast Fossil
Cast Fossil
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Stromatolites
Stromatolites
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Biomarkers
Biomarkers
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Biostratinomy
Biostratinomy
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Disarticulation
Disarticulation
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Abrasion
Abrasion
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Fossil Hash
Fossil Hash
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Traction Currents (Bedload)
Traction Currents (Bedload)
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Unimodal Orientation
Unimodal Orientation
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Study Notes
- Stromatolites: Fossilized bacterial structures
- Built by cyanobacteria in environments where grazers are excluded
- High salinity, high water temperature, strong currents
- Abundant before grazing animals evolved (Precambrian)
- Bacteria cover the sediment surface with microbial mat
- Trap carbonate mud and/or precipitates from seawater to build low domes
- High areas grow faster than low areas
- Relied increases upward to form stromatolite
- Thrombolites: Unlaminated, clotted microbial build ups
- Trace fossils: Tracks, Trails, Burrows, Borings
- Coprolites
- Biomarkers: chemical evidence of life
- Diagenesis
- Hopanepolyol: organic compound from the cell walls of bacteria
- Hopane: organic compound derived from hopanepolyol
- Cholesterol can indicate animal kingdom
- Biostratinomy: from death to final burial
- Loss of biological info
- Gain of info on the depositional environment
- Processes
- Disarticulation—joints removed
- Complete arthropods and echinoderms can only be preserved through obrution (burying)
- Progressive crinoid disintegration due to scavenging
- Complete calyces and stems
- Partial stems and disarticulate columnals
- Disarticulated columnals (most common)
- Abrasion—wear from transport
- Fossil hash
- Bivalves hold up stronger
- Measured using Mohs Hardness Scales
- Sand grains: Quartz (7)
- Bivalve Shell: Calcite (3)
- Transport of shells
- By traction currents (bedload) = extensive abrasion
- In suspension = minimal abrasion
- Storm beds
- Turbidites
- current/flow with higher density (lots of sediment)
- Reorientation—currents/waves align shells
- Unimodal orientation: all apices point in the same direction
- Disarticulation—joints removed
- Phosphate: Vertebrate bones, conodonts, inarticulate brachiopods
- Chitin/collagen: Arthropods, graptolites
- Cellulose: Wood, plant material
- Altered hard parts
- Recrystallization: change in crystal structure, but no change in chemical composition
- Can also be accompanied by loss of water in the mineral
- aragonite(CaCO3) → LMC(CaCO3)
- silica→quartz(water loss)
- Any mineral (fine crystals→coarse crystals)
- Carbonization: heat and pressure remove volatile elements, leaving a carbon film
- Left with resistant and stable parts of molecule
- Ex. coal (black) or graphite (silver)
- permineralization (petrification): pores of skeleton infilled w/ minerals that precipitate out of fluids
- Turn something into stone
- Won't burn
- Ex. silicified wood, permineralized dinosaur bones
- Replacement: original skeleton dissolves while precipitating a new mineral
- Common replacement minerals:
- dolomite (carbonate mineral)
- silica (opal)
- pyrite (anoxic conditions)
- limonite/goethite (iron hydroxides)
- Common replacement minerals:
- Recrystallization: change in crystal structure, but no change in chemical composition
- Leached Fossils: original shell dissolves, leaving a void or filling with minerals
- Common in molluscs (aragonite dissolves easily)
- Types of fossil molds:
- Steinkern (core)
- Internal features only
- muscle attachments
- Most common
- pops out
- 3D
- Cast
- Internal and external features
- full replica
- 3D
- Replica
- External features only
- 3D
- Mold
- External features only
- Preserves shell structure
- 2D
- Steinkern (core)
- Biogenic Structures
- Biostratification
- Hierarchical Classification of Life
- Domain, Kingdom, Phylum, Subphylum, Class, Oder, Family
- Taphonomy—fossil preservation
- Taphonomy: changes between an organism's death and discovery as a fossil
- controls fidelity of the fossil record
- provide important environmental information
- Paleoecology: study of fossilized organisms, their life, and their environment
- Fossil: any object that provides evidence of prehistoric life
- Types of fossils
- Physical remains: shells, bones, hardparts
- Mineral replacements: bodies/skeletons replaced by minerals
- Biological impressions: tracks, trails, burrows
- Chemical signatures: biomarkers indicating life
- Modes of fossil preservation (from least to most information loss)
- Unaltered soft parts
- Altered soft parts
- Unaltered hard parts
- Altered hard parts
- Leached fossils
- Biogenic structures
- biomarkers
- Soft Part Preservation
- Unaltered soft parts: no change to organic tissues except water loss
- Preservation methods (restricted to relatively recent Earth history)
- Freezing
- Mummification—dehydration/desiccation (water removed from tissue)
- Conservation traps—no longer exposed to water or air that degrade them
- Preservation methods (restricted to relatively recent Earth history)
- Altered soft parts: carbonization or mineralization of organic tissues
- Examples through Phanerozoic
- Preservation conditions
- Anoxia: oxygen depletion
- Obrution: rapid burial
- Fossil Lagerstatten ("motherlodes" of fossils): great preservation of soft tissues and articulated hard parts
- Hard Part Preservation
- Unaltered hard parts: original mineral composition remains intact
- Calcite (LMC): Brachiopods, bryozoans, paleozoic corals, echinoderms
- Aragonite: Molluscs, modern corals
- Silica: Radiolaria, diatoms, some sponges
- Current flowing in one direction
- Can't identify direction
- Bimodal orientation: apices pointing in two directions (180 apart)
- Oscillating current
- Shell flips after a threshold
- Concave-down orientation = wave or current activity
- Current with threshold flipped them over
- No preferred horizontal orientation = waves/currents were strong enough to flip the shells, but too weak to orient them
- Strong bimodal orientation = strong wave action
- Concave-down orientation = wave or current activity
- Dissolution—shells dissolve in cold/freshwater
- Can also occur prior to burial
- Transportation
- Indigenous
- Found in the same environment they lived in
- Shuffled around, but close info to what was living there
- Used in paleoecology and biostratigraphy
- Exotic
- Transported from different, but (same time) environment
- Diff communities mixing and deposited together
- Deposited by storms, used in biostratigraphy only
- Reworked (remanie)
- Fossils from older rocks mixed with new sediments
- Can mislead age dating
- Indigenous
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Description
This lesson explores the interpretation of fossil shell orientations in sedimentary rocks to infer past environmental conditions. It also defines key taphonomic processes related to shell preservation and transport.
