GEOL 337 Lecture Notes: Fossil Preservation & Paleoecology PDF

GEOL 337—MIDTERM NOTES Hierarchical Classification of Life (King Phillip Came Over For Good Soup) Domain, Kingdon, Phylum, Subphylum, Class, Order, Family Taphonomy—fossil preservation Taphonomy: changes between an organism’s death and discovery as a fossil ○ controls...

GEOL 337—MIDTERM NOTES Hierarchical Classification of Life (King Phillip Came Over For Good Soup) Domain, Kingdon, Phylum, Subphylum, Class, Order, 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) 1. Unaltered soft parts 2. Altered soft parts 3. Unaltered hard parts 4. Altered hard parts 5. Leached fossils 6. Biogenic structures 7. 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 Altered soft parts: carbonization or mineralization of organic tissues ○ Examples through Phanerozoic ○ Preservation conditions Anoxia: oxygen depletion Obrution: rapid burial Fossil Largerstätten(“motherlodes” of fossils): great preservation of soft tissues and articulated hard parts Hard Part Preservation Unaltered hard parts: original mineral composition remains intact Mineral Organisms Calcite(LMC) Brachiopods, bryozoans, paleozoic corals, echinoderms Aragonite Molluscs, modern corals Silica Radiolaria, diatoms, some sponges  Phosphate Vertebrate bones, conodonts, inarticulate brachiopods chitin/collagen Arthropods, grapolites 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) Leached Fossils:original shell dissolves, leaving a void or filling with minerals Common in molluscs(aragonite dissolves easily) Types of fossil molds Type Features 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 Biogenic Structures 1. Biostratification  Stromatolites: Fossilized bacterial structure ○ Built by cyanobacteria in environmental where grazers are excluded High salinity, high water temp, 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 2. Trace fossils: Tracks, Trails, Burrows, Borings 3. 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 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  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 ○ Dissolution—shells dissolve in cold/freshwater Can also occur prior to burial ○ Transportation Type Definition Example Indigenous - Found in the same environment they lived in Used in paleoecology and - shuffled around, but close info to what was living there biostratigraphy Exotic - Transported from different, but (same time) environment Deposited by storms, used in - diff communities mixing and deposited together biostratigraphy only Reworked - Fossils from older rocks mixed with new sediments Can mislead age dating (remanie) Paleoecology–evolution of ecosystems Environmental changes(big and small) Helps understand ecosystem evolution and limiting factors Explains how modern ecosystems respond to climate change Shows how ecosystems become complex over time Limiting factors: control species presence and abundance Category Factors Sedimentologic - Grain size - Substrate consistency - Turbulence - Turbidity Metabolic - Temperature - Light - Salinity - Oxygen Combination - Depth Sedimentologic factors Grain size: influence type and abundance of organisms epifauna(surface) - sand: mobile(moves with waves) - mud and gravel: less mobile(easier to attach)  infauna(burrowers) - sand: easiest for burrowing - gravel: hardest for burrowing Substrate consistency: how cohesive the grains are ○ Most important factor affecting benthic organics Category epifauna(surface) infauna(burrowers) Hardground Mobile or sessile Live in borings (rock/shell) attached/cemented Firmground Mobile or sessile Excavated dwelling burrows (stiff mud) Must attach No roots go into the surface Softground Mobile or sessile Abundant feeding/dwelling (loose sediment) Adaptations to avoid sinking(increased SA) burrows Soupground Mobile or absent little/no burrowing (soupy mud) No bearing capacity Turbulence: water agitation ○ Highers in shallow environments ○ Favours filter-feeders Water movement bringing food and water to sessile organisms ○ Harmful to fragile/branching organisms Turbidity: suspended sediment ○ Harmful to filter-feeders Clogs respiratory/feeding systems ○ No effect on deposit feeders Metabolic factors Factor Details Light - affects photosynthesis and vision - sunlight diminishes in quantity and wavelength spectrum with depth - influences distribution of organisms Salinity - seawater: 35‰ - freshwater: 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(17 000 fossil species Living cephalopods ○ Exclusively marine ○ Ambush predators ○ Major groups nautiloidea(nautilus) Coleoidea(cuttlefish and squid and octopus) Soft part anatomy Tentacles: capture prey with suckers or hooks for grasping Eye: well-developed and similar to vertebrate eyes, excellent vision Radula: rasping structure for scraping food ○ Helps them eat softer prey and handle more delicate food Funnel/siphon: locomotion via jet propulsions and water expulsion Siphuncle: regulates buoyancy by controlling gas and fluid exchange in the chambers of the shell ○ Allow the animal to adjust its position in the water column ○ In cephalopods with shells Reproduction Sexual Juvenile stages differ from adult morphology Adults show no change in morphology during growth(only inflation) Juvenile→preadult→(sexual maturity) →adult→(reproduction) →egg→(hatching) →neanoconch Molluscan shell microstructure Organic layer(periostracum): outermost, impermeable barrier Prismatic layer: vertical aragonite crystals Nacreous layer: thin interlayers of aragonite and chitin, very strong ○ Growing brick-and-mortar structure—multilayered proteins and chitin slowly mineralize by microscopic mineral “bricks” which eventually form dense nacre Shell anatomy of nautilus External ○ Aperture: where soft body and tentacles emerge from the shell ○ Peristome: raised or flared margin that encircles the aperture ○ Growth line: represent stages of the cephalopod’s growth Internal  ○ Chambers: provide buoyancy control by filling with gas or liquid ○ Septa: internal walls that separate shell into chambers ○ Phragmocone: gas-filled part of shell aids in buoyancy regulation ○ Body chamber: living space where the nautilus resides ○ Siphuncle: regulates gas and fluid exchange between chambers to control buoyancy ○ Septal foramen: opening in each septum through which the siphuncle passes Cephalopod shell form All living and most fossil cephalopods exhibit planispiral coiling Some cretaceous ammonites were completely coiled(heteromorphs) Cephalopod ornamentation and sutures Ornamentation ○ Growth lines in all cephalopod shells Grow by secreting new shell at their aperture ○ Ribs, ridges, nodes, and spines ○ Visibility Most ornamentation only shows on the external surface of the shell Made of aragonite usually not visible on internal molds or steinkerns(sediment-filled internal casts) Ornamentation degree ○ varies between species and environmental adaptations highly sculpted shells for protection or hydrodynamics, while others have smoother shells  1: creates vortices, reduces speed 2: maximizes speed 3-4: coarse ornamentation reduces speed but increases protection Flume experiments: drag coefficient on cephalopod shells Smooth shells create backflow that reduces speed ornamentation(ribs, ridges, nodes, spines) disrupts backflow, reducing turbulence and enhancing predator defense Suture: line formed where the septa(internal walls) meet the shell’s inner surface suture complexity in diminishing strain and stress in ammonoid phragmocone Increasing complexity increase resistance to implosion and attack ○ Suture line: pattern of the suture when viewed in cross-section Saddle: convex towards aperture Lobes: convex towards protoconch(apex) Preservation of nautilus Outside: displays external ornamentation Inside: shows internal septa(dividing the shell into chambers) Steinkern: preserves the shape of internal structures ○ Often revealing suture patterns Cephalopod subclasses Based on shell form and soft parts Subclass Suture type Siphuncle Shell shape Morphology Key features Nautiloidea Nautiloid Straight - longicones - chamber - cameral deposits common (orthoceratoid) cylindrical - brevicones - septum - orthoconic specimens common in the Kingston area - convolute - siphuncle - ordovician nautiloids(orthoceratoids) - involute - extinct genera: michelinoceras and oncoceras Tarphyceratoidea Nautiloid Simple Coiled - early coiled cephalopods (order) (orthoceratoid) - less common than nautiloidea Endoceroida Nautiloid Large - longicones - ventral - large predators of the Ordovician sea (order) (orthoceratoid) Eccentric siphuncle (up to 10 m long) Cylindrical - septa - closely spaced chambers Endocones - siphuncle - common in the kingston area endoconic - extinct genus: endoceras Actinoceratoidea Nautiloid Beaded Longicone - septum - common in Kingston (order) (orthoceratoid) (orthoconic) - cameral - commonly cameral or siphuncular deposits deposits - extinct genus: actinoceras Bactridoidea Simple Ventral Orthoconic - globular - minor group (order) (nautiloid-like) protoconch - ancestral to ammonoidea and coleoidea Ammonoidea Ammonoid Ventral Varies - important in biostratigraphy (complex) Mostly coiled - soft parts resemble squid/octopus - lituiticone - gyrocone - tarphycone (evolute) - convolute - involute Coleoidea Absent or N/A Internal or - includes modern squid, octopus, cuttlefish, and extinct internal shell absent belemnites Ecospace of many cephalopods Tiering: pelagic(in the water column) Motility level: freely, fast Feeding mechanisms: predatory Biostratigraphy Ammonites useful for dividing Jurassic period into biostratigraphic zones less than 1 M yrs long Ammonoid cephalopods are crucial for biostratigraphy from the Permian to Creataceous ○ To a lesser extent in the Devonian and Carboniferous Other cephalopod groups also contribute to biostratigraphy ○ belemnites(useful in the Jurassic and Cretaceous) ○ Orthoceratoids, endoceratoids, and actinceratoids(used in the Ordovician and Silurian) Why cephalopods provide the most precise biostratigraphy 1. Rapid rates of speciation and extinction: evolve quickly, making them great markers for short time periods 2. Pelagic nature: being pelagic, they are broadly distributed across the world’s oceans in many regions 3. Abundance: relatively abundant in fossil records 4. Readily recognizable: easily identifiable features, making them great indicators for precise dating Predators invade the pelagic realm Time period Predators? Notes Neoproterozoic No - benthos - larger animals, metazoans Cambrian - demersal predators - demersal + tiering - agronomic substrate revolution - cambrian explosion Ordovician - demersal predators - ordovician biodiversification - cephalopods - macroplanktons - evolutionary trend towards tightly coiled shells start Silurian - demersal predators - cephalopods Devonian - demersal predators - nekton - cephalopods - nekton revolution - fish Cephalopod shell shape, buoyancy and stability Problem: need to maintain buoyancy while ensuring stability for movement in the water column Chambered shells provide buoyancy, but center of buoyancy and center of gravity weren’t always aligned ○ If too far apart, the organism would become unstable and tip over Solutions: ○ Endocones: internal deposits in siphuncle could help balance buoyancy ○ Beaded calcified siphuncle(actinoceratoidea): reinforced siphuncles to help regulate gas exchange ○ Cameral deposits: mineralized deposits within shell chambers to adjust weight distribution ○ Ascocones: chambered shell adaptation, potential aiding in buoyancy control ○ Brevicone: short, conical shell that may have provided better stability at the cost of speed ○ Coiling Tighter coils(involute): improve stability Looser coils(evolute): enhance maneuverability Planispiral shapes and variations ○ Evolution favoured different shell structures for speed, stability, or defense ○ Nautilus is only surviving externally shelled cephalopod due to balance of buoyancy and stability Shape parameters Parameter Formula Effect Whorl expansion rate(W) W=(b/a)2 W=1: perfect disc(high stability) W>1: stretched out shape(higher speed) Aperture distance from D=c/b Small D: involute(tight coiling) axis(D) Large D: evolute(looser coiling) Whorl cross-section S=e/d S=1: circular(resists implosion) shape(S) S55% of Arctic biomass and >90% of deep-sea biomass produce >1B tonnes of CaCo3/year Type Characteristics Planktonic foraminifera - live in water column - LMC shells - small and short-lived - limiting factors: temp and salinity - tests designed to slow sinking Benthic foraminifera - live on/in sediment surface or attached to plants/algae - HMC/aragonite shells/agglutinated sand grains (not as stable) - larger prefer oligotrophic reefs and carbonate shoal environments - most large foraminifera contain photosynthetic endosymbionts 1. Dinoflagellates 2. Diatoms 3. Red algae 4. Green algae Why endosymbionts? 1. Energy from photosynthesis: utilizing sunlight gives an energetic advantage 2. Photosynthesis promotes calcification: helps them make larger shells faster 3. Removal of waste: symbionts help larger foraminifera with waste removal by taking up waste Building a foram test: 1. Shell wall Agglutinated: takes particles and glue them together Porcelaneous: order calcite crystals(porcelain) Hyaline: crystals are perpendicular to test walls(glassy) 2. Chamber arrangement: wide variation 3. Aperture style: position and style Foraminifera evolution  Group Time period Key features Allogromiida First to evolve no test(bas fossil record) Texturlariida cambrian—recent Agglutinated test Fusulinia ordovician—permian First to form their own shell Globigerinida jurassic—recent Plankton Majority of foraminifera in oceans Foraminifera suborders Suborder Time period Test type Key features testulariina Cambrian— Agglutinated - variable shell form and grain size recent Organic or - textularia mineralized - haplophragmoides Fusulinina Carboniferous calcareous - large(few mm), spindle-shaped – - photosynthetic endosymbionts permian - prominent paleozoic group - shallow illuminated water - fusulinids(carboniferous–permian) Miliolina Carboniferous porcelaneous - distinctive coiling — - symbionts recent - Some modern taxa large - pyrgo - quinqueloculina Lagenina Silurian— porcelaneous - distinctive aperture recent calcite Rotaliina Triassic– Hyaline calcite - discoid shape recent - large orbitoid rotaliina with symbionts(cenozoic)---nummulites -pyramids -nummulites in paris basin and carpathian alps to infer strata were the same age and the first biostratigraphic correlation - paleontological obsession globigerinina Middle Hyaline - planktonic jurassic— - depth-dependent forms recent -shallow