Fossils and Preservation methods

Hierarchical Classification of Life

• The classification includes domain, kingdom, phylum, subphylum, class, order, and family
• A mnemonic to remember the order is: King Phillip Came Over For Good Soup

Taphonomy and Fossil Preservation

• Taphonomy refers to the changes an organism undergoes from death to discovery as a fossil and controls the fidelity of the fossil record
• It can provide environmental information
• Paleoecology is the study of fossilized organisms, their lives, and their environment
• A fossil constitutes any object that provides evidence of prehistoric life, including physical remains like shells, bones, and hardparts

Types of Fossils

• Fossil types: physical remains, mineral replacements, biological impressions, and chemical signatures

Modes of Fossil Preservation

• The modes of fossil preservation (from least to most information loss) includes: unaltered soft parts, altered soft parts, unaltered hard parts, altered hard parts, leached fossils, biogenic structures, and biomarkers

Soft Part Preservation

• Unaltered soft parts undergo no change to organic tissues except water loss
• Preservation methods restricted to relatively recent Earth history and includes freezing, mummification (dehydration/desiccation), and conservation traps

Altered Soft Parts

• Here, carbonization or mineralization of organic tissues occurs
• Examples are seen through the Phanerozoic
• Preservation occurs when there may be either Anoxia: oxygen depletion and/or Obrution: rapid burial
• Fossil “motherlodes” (Lagerstátten) show great preservation of soft tissues and articulated hard parts

Hard Part Preservation

• Unaltered hard parts retain their original mineral composition
• Calcite (LMC) is found in brachiopods, bryozoans, paleozoic corals, and echinoderms
• Aragonite is found in molluscs and modern corals
• Silica is found in radiolaria, diatoms, and some sponges
• Phosphate is found in vertebrate bones, conodonts, and inarticulate brachiopods
• Chitin/collagen is found in arthropods and grapolites
• Cellulose is found in wood and plant material

Altered Hard Parts

• Recrystallization alters the crystal structure but not chemical composition
• Recrystallization can be accompanied by the loss of water in the mineral: Aragonite (CaCO3) transforms into LMC (CaCO3), and silica transforms into quartz (with water loss)
• Carbonization occurs when heat and pressure remove volatile elements, leaving a carbon film composed of resistant and stable parts of a molecule, such as coal (black) or graphite (silver)

Permineralization

• During petrification, pores of the skeleton are infilled with minerals that precipitate out of fluids
• Won't burn
• Example: silicified wood, permineralized dinosaur bones
• Replacement occurs when the original skeleton dissolves while precipitating a new mineral
• Common replacement minerals include dolomite (carbonate mineral), silica (opal), pyrite (anoxic conditions), and limonite/goethite (iron hydroxides)

Leached Fossils

• Here, the original shell dissolves leaving either a void or a filling with minerals
• This is common in molluscs (aragonite dissolves easily)

Types of Fossil Molds

• Steinkern (core) retains internal features only, such as muscle attachments, it is the most common type, 'pops' out, and is 3D
• Casts shows internal and external features, is a full 3D replica, is 3D
• Replicas have external features only, is 3D
• Molds have external features only, preserve shell structure, and is 2D

Biogenic Structures

• Structures include: Biostratification, Stromatolites, and Thrombolites
• Stromatolites are a fossilized bacterial structure built by cyanobacteria in environments where grazers are excluded and commonly found in high salinity, high water temp, and strong currents

Before Grazing Animals Evolved

• Bacteria cover the sediment surface and traps carbonate mud and/or precipitates from seawater to build domes, growing faster in high areas than lower areas

Stromatolite Reliance

• Increases upward to form stromatolite
• Thrombolites are unlaminated, clotted microbial build ups

Trace Fossils

• Includes tracks, trails, burrows, and borings

Coprolites

• This constitutes chemical evidence of life discovered from diagenesis, hopanepolyol (organic compound from cell walls of bacteria), hopane (organic compound derived from hopanepolyol), and cholesterol (can indicate animal kingdom)

Biostratinomy

• Happens from death to final burial which results in loss of biological and gain of info on the depositional environment
• Processes involves disarticulation and abrasion

Disarticulation

• Joints removed are best preserved though obrution
• Progressive crinoid disintegration due to scavenging: complete calices and stems, partial stems and disarticulate columnals, disarticulated columnals (most common)

Abrasion

• Wear resulted from transport
• Creates fossil hash

Bivalve Abrasion

• Bivalves hold up stronger than others
• Measured using Mohs Hardness Scales

Transport of Shells

• Occurs by traction currents (bedload), generating extensive abrasion
• In suspension minimizes abrasion
• The following facilitates suspension: storm beds, turbidites, current/flow with higher density (lots of sediment)

Reorientation of Currents/Waves

• Aligns shells
• Unimodal orientation: apices point in one direction indicating current flowing in one direction and the inability to identify the direction
• Bimodal orientation: apices point in two directions (180 apart), exhibiting Oscillating current

Shell Orientation

• Direction is determined by wave or current activity given shells flip after a threshold
• Concave-down orientation is wave or current activity

Current Threshold

• In this state with threshold flipped over, no preferred horizontal orientation and waves or currents strong enough to flip the shells but too weak to orient them
• Strong bimodal orientation exhibits strong wave action

Dissolution of Shells

• Occurs when shells dissolve in cold and/or freshwater, and/or prior to burial

Transportation - Type and Definition

• Indigenous fossils are found in the same environment they lived in and are shuffled around (but close info to what was living there), used in paleoecology and biostratigraphy
• Exotic fossils were transported from a different environment at the same time and communities mixing and being deposited together, deposited by storms, used in biostratigraphy only
• Reworked (remanie) fossils are from older rocks mixed with new sediments, and can mislead age dating

Paleoecology

• This involves evolution of ecosystems with environmental changes which helps to understand ecosystem evolution, explaining how modern ecosystems respond to climate change and shows how ecosystems become complex over time

Limiting Factors

• Control on the species presence and abundance in ecosystems
• These factors include sedimentologic, metabolic, and combination

Grain Size

• Influences type and abundance of organisms.
• Sand: mobile (moves with waves)
• Mud and gravel: less mobile (easier to attach)

Substrate Consistency

• How cohesive the grains are in the sediment
• Most important factor affecting benthic organics
• Sand: easiest for burrowing
• Gravel: hardest for burrowing

Benthic Organics

• Organics divided into epifauna (surface organisms ex, hardground) and infauna (burrowers - ex, soft ground)

Turbulence

• Water agitation is more prevalent higher in shallow environments
• Favors filter feeders
• Water movement bringing food and water to sessile organisms
• Harmful to fragile/branching organisms

Turbidity

• Suspend sediment is detrimental to the filter-feeders which inhibits feeding and respiratory systems
• No effect on deposit feeders

Metabolic Factors

• Light and depth affect photosynthesis and vision
• Sunlight diminishes in quantity and wavelength spectrum with depth
• Influences distribution of organisms

Salinity

• Seawater: 35 ‰
• Freshwater: <0.5 ‰
• Euryhaline: 30-40 ‰
• Freshwater and euryhaline environments have the best diverse life
• Shelly animals are diverse in freshwater and normal marine environments

Salinity Limiting Factor

• In response to this, there is a decrease in both species, size (which is in line with the decrease in salinity)
• Oxic environments (>1 ml/L): abundant fossils, predators common
• Disoxic (0.1-1 ml/L): few fossils, burrows (soft-bodied animals) only, predators are rare (require lots of E), few shelly fossils (affect ability to respire/metabolize)
• Anoxic (<0.1ml/L): no metazoan life
• Size of soft bodied animals decreases as oxygen decreases

Light Zones

• There exits euphotic(sunlight zone), disphotic(twilight zone) and aphotic(midnight zone)

Combination Factors

• Depth is solely controlled by pressure small grain size, less turbulence, less light intensity, lower temperature, lower oxygen (then higher at greater depths), and higher body size

Ecological Concepts

• Individual: single organisms, population, community, and ecosystem

Ecological Concepts - Definitions

• Population: group of same species in one area and or time
• Community: all populations in one area and or time
• Ecosystem: interaction of living and nonliving components

Torphic Chains and Webs

• Trophic chain: this is the energy and matter flow from one organism to another
• Chemoautotrophs get its energy from breaking down organic matter
• Begins with green plants or phytoplankton Always

Trophic Levels

• It explains levels of the food chain Autotrophs (first level), Herbivore(second Level), Carnivore(3rd Level), and Function at 2 or more trophic levels (Omnivores)
• Trophic webs: Interacting trophic chains showing both of these are integrated full energy and matter flow in a community

Marine Paleoecology

• The study of tiering levels of marine animals are divided into three main groups, defined by sea floor and habitat Pelagic group lives in the water column benthic group lives on/in the bottom of the sea

Pelagic Groups

• Pleustonic/Neustonic are marine organisms that live in the water
• Planktonic are floaters Nektonic are swimmers

Bambach-Bush Ecospace Cube

• Describes ocean terrain factors related to organism habit, motility and survivability on the sea floor or the ocean; includes Y-axis relating to seafloor, X-axis representing food/feeding strategy, Z-axis is motility based

General Factors of Paleoecology in Earth Terrains

• Limiting Factors : throughout marine, fresh and marine terrestrial systems
• Fossil Record: the record remains more complete marine
• Terrestrial: Uses proxies (isotopes/microfossils, marine, fresh and isotope based herbivority

Behavioral Trace Fossils

• Useful for paleoecology, ichnofossil classification relates more to patterns in the surface and underground environment

Ichofossil formation

• Ichofossil formation is effected by animal habitat and other outside factors in nature. The animal behaviour causes variance in environment

Paleosols

• A collection of different layers of earth that make up a fossilized environment.

Classification of Ichnofossils

• Feeding traces (foodichna)
• Farming burrows (agrichnia)
• Wellings and Dwelling burrows are closely spaced meabders that indicate low nutrient level
• Grazing traces includes walking trails that indicate dinosaur or triol bite track ways.
• Resting traces and include fossils like the "anemone bases"
• Preditation traces include the shells of shellfish
• Spretien is used for the reworking and shifting the of burrow

Environmental Change with Depth

• As Depth Increases light/light limitation in oceans
• universal Ichnofacies; Ichnofacies indicates environment
• substrate and depth are 2 main contributors

General description of the main contributing environments on a substratum

Firmground, harding and woodgroup

Deep water groups

Skolithos, Cruziana. Zoophycos and Nereites

Sea Level change and Ichnofacies

• Shalllow marine , recorded in deep an shallow facies
• Sediment movement occurs during movement of water and environmental transition

Bivales Phylum

• Mollusls second most diverse and can live anywhere on earth
• Bivales can fossilize
• Why Study Bivalves? Everyday life, great for fossilization, functional morpholly

Bivales evolution and Features

• Bivales evoleved from the Monoplacophora to sketch

General Bivalve Morphology

• Includes features such as the soft mantel and well developed brain

Common Features in all bivales shell structures

• There is an under tension, and needs a muscle to close which provides some degree movement

Bivalve Distinguishabilty

• In distinguishing Bivales the anterior asymmtotry points to the opposite of the posterior

Bivalve Dentition

• Numerous subequal teeth • Bivale Orientation: key features are found on the left/right side of shell
• Muscle attachment points along linges

Bivales - The Internal Supports

• Include features such as the shell.

Bivale shell Ornamentation

• Growth lines: this bivalve are have caused geochemistry look at through climite

Geological history

• Bivales increased steasidy where as other types in sea declined

Trace Elements - Paleoecology

• The study of terranes of varying conditions where Bivales survived from

Bivales Classifications

• Is heavily based on geological timeline but not by the traits of the animals themselves

Bictivalvular shell

• A bivalve that has features from different species

Marine Biota

• Bivalve habits and life categorized by habitat and life style
• Bysally are organisms the attack to seal flow to to sea floor , bysattes modern typically

Various Lifestyles

• Most have been replaced, Bysallery/Modern species that can be cemented in water

Features of Sea Bottom

• Hard Bottom- Thin streamline rock
• Surficial erect cemented by oyster reef

Shell Thickness

• Shell thickness also matters most are borers in wood with modified dents

Various Other Molluiks life Styles

• Thin lining and streamlined shapes allow species to thrive
• Pecten attach their bivallery life to the bottobm by Narrow umbonal and umbonal by swimming (large muslces , symemtrcal , stability

Shape and Life of the Various Moluisks

• Different shapes indicate stability, with high degree angles in certian species.

Cephalopods

• Exlusivily marive and major groups
• Cephalopod have capture prey with tentacles

Shells in Cephalopods

• Have allow the animal to stay in water with various shells

Cephalopods Reproduction

• Reproduce to Sexual and change in morphone

Molluscan

• The surface of the organic layer provides some degree of strong
• Molluscan sheels provides some key detail and growth patterns

Cephalopods shell form

• Most are coilings , some heteromorphs

Cephalopods ornamentation and Steris

• Growth patters and Sterris allow for cephalood movmement

General notes the steris types.

• A key part of how to understand what Steris type.

Perservation of Nautilus

• Preserves outisde and inside elements

Cephalopod Subclasese'

• Provide precise geo time stamps

Ecology

• Various deep water habitats, help species survival in sea

Mesoic Ammoniod Morphospace

• General Contours and evolutionary pressures guide shells in varying degrees

Evolution of Ornamenetions

• As animal become more capable some have to adapt and develop "defensive features"

Top Species

• Morphology and general behaviour are key in survival

This lesson explores the process of fossilization. It covers various preservation methods like freezing, mummification, anoxia, and obrution. It also discusses the classification of life.