GS 421 Lecture Notes on Micropaleontology PDF

Page |1 GS 421 Lecture Notes Introduction to Micropaleontology and Microfossils Lecture 1 1. What is Micropaleontology? Micropaleontology is the branch of paleontology that focuses on the study of microscopic fossils (...

Page |1 GS 421 Lecture Notes Introduction to Micropaleontology and Microfossils Lecture 1 1. What is Micropaleontology? Micropaleontology is the branch of paleontology that focuses on the study of microscopic fossils (microfossils). These are fossils that typically require a microscope for observation due to their small size, ranging from a few microns to a millimeter in diameter. Microfossils provide invaluable insights into past environments, climate changes, and biostratigraphy, aiding in the exploration of oil, gas, and other mineral resources. 2. What are Microfossils? Microfossils are the remains of microorganisms or tiny fragments of organisms that lived millions of years ago. They are typically classified based on their chemical composition and biological origin, and they are important indicators of past geological and environmental conditions. Microfossils are found in a variety of sedimentary rocks, including limestone, shale, and chert. 3. Typical Lithologies Microfossils are Found In: Limestone: Rich in calcareous microfossils such as foraminifera and coccolithophores. Shale: Often contains organic microfossils like spores and pollen, as well as siliceous microfossils like radiolaria. May also have foraminifera beautifully preserved GS 421 Paleontology Micropalaeontology Jahnavi Punekar  Page |2 Chert: Commonly contains siliceous microfossils such as diatoms and radiolaria. Phosphatic Deposits: Known for preserving conodonts. 4. Classification of Microfossils: Microfossils are classified based on their composition and the organisms: Inorganic Microfossils – 4.1 Calcareous Microfossils: These microfossils are composed primarily of calcium carbonate. a. Foraminifera- What are they? Unicellular protists that secrete calcareous shells, called tests. Habitats: Found in both marine environments, with planktic species floating in the water column and benthic species living on or near the seafloor. Fossil Locations: Commonly found in limestones and shales. Geologic Age Range: Cambrian to present. Preservation Criteria: Foraminifera preserve well in carbonate-rich sediments; their tests may dissolve in acidic conditions. Trivia: Foraminifera are important biostratigraphic markers and are used extensively in oil exploration. b. Calcareous Nanoplankton (Coccolithophores) What are they? Single-celled algae that produce calcium carbonate plates called coccoliths. Habitats: Marine, predominantly in surface waters. GS 421 Paleontology Micropalaeontology Jahnavi Punekar  Page |3 Fossil Locations: Found in chalks and marly limestones. Geologic Age Range: Upper Triassic to present, prominent only after Jurassic and thrived during Cretaceous Preservation Criteria: Excellent preservation in carbonate-rich sediments, though coccoliths can be destroyed in highly acidic environments. Trivia: The famous White Cliffs of Dover are largely composed of coccolithophores. c. Ostracods- What are they? Small crustaceans with calcareous bivalve-like shells. Habitats: Marine, freshwater, and brackish environments. Fossil Locations: Common in limestones, shales, and marls.- Geologic Age Range: Cambrian to present. Preservation Criteria: Ostracod shells preserve well in fine-grained sediments, especially in anoxic conditions. Trivia: Ostracods are often referred to as "seed shrimp" due to the shape of their shells. 4.2 Siliceous Microfossils These microfossils are composed of silica (SiO₂). a. Radiolaria- What are they? Single-celled marine protists with intricate silica skeletons. Habitats: Found in all oceanic environments, particularly in deep waters. GS 421 Paleontology Micropalaeontology Jahnavi Punekar  Page |4 Fossil Locations: Common in deep-sea cherts and radiolarian oozes. Geologic Age Range: Cambrian to present. Preservation Criteria: Silica dissolves in alkaline conditions, but radiolaria preserve well in siliceous oozes and cherts. Trivia: Radiolarian skeletons are some of the most elaborate and geometrically complex microfossils. b. Diatoms- What are they? Single-celled algae with siliceous cell walls known as frustules.- Habitats: Marine and freshwater environments, typically in surface waters. Fossil Locations: Found in siliceous oozes, diatomaceous earth, and some shales. Geologic Age Range: Jurassic to present. Preservation Criteria: Diatoms preserve well in sediments with low rates of dissolution, especially in cold waters. Trivia: Diatoms are major contributors to global oxygen production through photosynthesis. 4.3 Phosphatic Microfossils These microfossils are composed of calcium phosphate. a. Conodonts- What are they? Microfossil remains of an extinct, eel-like vertebrate with tooth-like elements composed of apatite. Habitats: Marine environments, primarily associated with open waters. GS 421 Paleontology Micropalaeontology Jahnavi Punekar  Page |5 Fossil Locations: Found in phosphatic deposits and some limestones. Geologic Age Range: Cambrian to Triassic. Preservation Criteria: Conodont elements preserve well in phosphatic deposits and are resistant to dissolution. Trivia: Conodonts are widely used for biostratigraphy, especially in Paleozoic and early Mesozoic strata. Organic Microfossils 4.4 Acritarchs- What are they? Organic-walled microfossils of uncertain biological origin, likely representing various algae.- Habitats: Marine environments. Fossil Locations: Found in shales and other fine-grained sediments. Geologic Age Range: Precambrian to present. Preservation Criteria: Acritarchs preserve well in anoxic conditions where organic matter is protected. Trivia: Acritarchs are some of the oldest known microfossils, with occurrences dating back over 1.4 billion years 4.5. Spores and Pollen- What are they? Reproductive structures of plants, including ferns, conifers, and flowering plants. Habitats: Terrestrial environments. Fossil Locations: Common in shales, coals, and other terrestrial sediments. Geologic Age Range: Ordovician to present. GS 421 Paleontology Micropalaeontology Jahnavi Punekar  Page |6 Preservation Criteria: Spores and pollen preserve well in fine-grained sediments under anoxic conditions. Trivia: Spores and pollen are key indicators for paleoclimatic and paleovegetation reconstructions. 4.6. Dinoflagellates- What are they? Single-celled marine plankton with organic-walled cysts. Habitats: Marine and, occasionally, freshwater environments. Fossil Locations: Found in marine shales and other fine-grained sediments. Geologic Age Range: Triassic to present. Preservation Criteria: Dinoflagellates preserve well in anoxic conditions where organic matter is not oxidized. Trivia: Dinoflagellates are responsible for modern-day "red tides," which are harmful algal blooms. 4.7. Scolecodonts- What are they? Fossilized jaws of polychaete worms. Habitats: Marine environments, particularly in benthic zones. Fossil Locations: Found in marine sediments, especially shales. Geologic Age Range: Cambrian to present. Preservation Criteria: Scolecodonts preserve well in fine-grained sediments under anoxic conditions. Trivia: Scolecodonts are valuable for reconstructing ancient benthic communities. GS 421 Paleontology Micropalaeontology Jahnavi Punekar  Page |7 4.8. Chitinozoa- What are they? Flask-shaped organic-walled microfossils, possibly representing egg cases of marine organisms. Habitats: Marine environments, particularly in deeper waters. Fossil Locations: Found in shales and other fine-grained marine sediments. Geologic Age Range: Ordovician to Devonian. Preservation Criteria: Chitinozoa preserve well in anoxic conditions where organic matter is protected from oxidation. Trivia: The biological affinity of chitinozoa is still debated, making them a fascinating subject of study in micropaleontology Lecture 2 Foraminifera and Environmental Controls on Their Distribution 1. What are Foraminifera? Foraminifera are single-celled protists that produce a test, or shell, primarily composed of calcium carbonate. These microorganisms are found in marine environments and play a significant role in the carbon cycle. Their tests accumulate on the seafloor after death and contribute to sedimentary rock formations such as limestone and chalk. Foraminifera can be broadly divided into planktic (floating in the water column) and benthic (living on or within the seafloor) species. 2. Where Do They Live? Planktic Foraminifera live in the open ocean, floating in the upper water column (epipelagic to mesopelagic zones). Benthic Foraminifera inhabit the GS 421 Paleontology Micropalaeontology Jahnavi Punekar  Page |8 seafloor, living either on the sediment surface (epifaunal) or within the sediment (infaunal). They are found in a wide range of marine environments, from shallow coastal waters to the deep sea. 3. Interesting Facts about Foraminifera Planktic Foraminifera Habitats: Found primarily in the upper 300 meters of the ocean, where sunlight can penetrate, although they can also occur at greater depths, even up to sub-thermocline. Interesting Fact: Planktic foraminifera are excellent indicators of past climate changes because their shell composition is influenced by the temperature and chemistry of the seawater they inhabit. Isotopic analysis of their tests provides a record of ocean temperatures and ice volume. Benthic Foraminifera Habitats: Benthic species are more diverse and can be found in environments ranging from intertidal zones to the abyssal plains of the deep ocean. Interesting Fact: Benthic foraminifera are essential indicators of oceanic productivity and oxygen levels. In oxygen-deprived environments, specific species that tolerate low-oxygen conditions (dysoxia) dominate the community. 4. Environmental Controls on Foraminifera Distribution The distribution of foraminifera, as well as other microfossils, is governed by physical, chemical, and biological factors. These factors influence not only their presence but also the composition of foraminiferal assemblages in different marine environments. 4.1 Physical Variables GS 421 Paleontology Micropalaeontology Jahnavi Punekar  Page |9 1. Temperature - Planktic Foraminifera: Species composition changes with temperature. Warm-water species dominate tropical and subtropical regions, while cold-water species are prevalent in polar and subpolar regions. Benthic Foraminifera: Deep-sea species tolerate colder, more stable temperatures compared to shallow-water species. Impact on Distribution: Temperature affects the calcification rate and test morphology of foraminifera, with some species thriving only in specific temperature ranges. 2. Pressure - Affects deep-sea benthic foraminifera, which are adapted to high-pressure environments of the abyssal plains. Planktic foraminifera are less affected by pressure due to their shallower habitats. 3. Light - Only affects planktic foraminifera indirectly, as some species have symbiotic algae that require light for photosynthesis. - Deep-sea benthic species are unaffected by light. 4. Depth - Depth influences the availability of food and the type of substrate, with planktic foraminifera living at various depths in the water column and benthic species living at different sediment depths. For planktic species, depth stratification also affects oxygen availability and temperature. 5. Substrate - Benthic foraminifera are highly substrate-specific. They prefer stable, fine-grained sediments in low-energy environments, but some species thrive on coarser sediments or hard substrates like rocks and shells. 6. Energy Conditions (Currents) – GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 10 Planktic Foraminifera: Ocean currents control the dispersal of foraminiferal shells, influencing their geographic distribution. Benthic Foraminifera: Strong currents can inhibit sediment accumulation and disturb benthic habitats, while low-energy conditions promote fine sediment deposition favorable to many benthic species. 4.2 Chemical Variables 1. pH - Acidic conditions (low pH) can lead to the dissolution of calcium carbonate shells, affecting both planktic and benthic foraminifera. Ocean acidification, driven by increasing CO₂ levels, poses a significant threat to their populations. 2. Dissolved CO₂ - High CO₂ concentrations lower pH and carbonate saturation, affecting calcification. Planktic foraminifera are particularly vulnerable to changes in CO₂ levels due to their reliance on carbonate to form their shells. 3. EH and Redox Conditions - In low-oxygen or anoxic environments, specific benthic foraminifera species thrive. Redox conditions, particularly in deep- sea settings, control the types of benthic foraminifera present. 4. Limiting Nutrients (Iron, Phosphorus, Nitrogen) - Nutrient availability affects primary productivity, which in turn controls the food supply for planktic foraminifera. In oligotrophic (nutrient-poor) regions, planktic species adapted to low-nutrient conditions dominate. 5. Carbonate Saturation - In undersaturated waters, calcium carbonate dissolves, leading to the poor preservation of foraminiferal shells. Higher GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 11 carbonate saturation enhances shell preservation in both planktic and benthic species. 6. Salinity - Foraminifera are highly sensitive to changes in salinity. Planktic species are most abundant in open-ocean, stable salinity environments, while benthic species can tolerate a range of salinities, from brackish estuaries to hypersaline lagoons. 4.3 Biological Variables 1. Competition - Both planktic and benthic foraminifera face competition for food resources. Species adapted to different ecological niches (e.g., depth, nutrient availability) coexist by minimizing direct competition. 2. Predation - Planktic foraminifera are preyed upon by zooplankton and small fish, while benthic species may be consumed by various benthic invertebrates. Predation pressures can influence the morphology and distribution of foraminiferal species. 3. Symbiosis - Some planktic foraminifera host symbiotic algae that provide additional nutrients through photosynthesis. This symbiotic relationship allows foraminifera to thrive in nutrient-poor surface waters. Symbiont Requirements: The symbionts require sufficient light and nutrients to survive, which limits their host foraminifera to the upper photic zone (above 100 meters). Summary: Foraminifera are sensitive indicators of past and present environmental conditions. Their distribution is controlled by a variety of physical, chemical, and biological factors, from ocean temperature and depth to competition and symbiosis. Studying these factors provides critical GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 12 insights into past climate changes, ocean circulation patterns, and marine ecosystems. Sampling Techniques in Micropaleontology 1. Types of Samples in Micropaleontology In micropaleontology, the success of analysis and interpretation depends on the collection of appropriate samples from various geological settings. Two primary types of samples are: 1.1 Outcrop or Surface Samples - These are samples collected from exposed rock formations at the surface of the Earth, typically from sedimentary rock layers visible in outcrops, riverbanks, coastal cliffs, or excavation sites. Application: Used to study surface geology, biostratigraphy, and paleoenvironmental interpretations, often representing recent to ancient depositional environments. Method: - Samples are taken directly from exposed rock layers. - For unconsolidated sediments, techniques like scraping or scooping are employed, while for hard rock, tools like hammers and chisels are used. Advantages: - Direct access to exposed stratigraphy, allowing for detailed stratigraphic context and correlation. - Cost-effective and easier to collect compared to subsurface samples. - Suitable for preliminary surveys and studies of surface geology. GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 13 Disadvantages: - Exposure to weathering and erosion may alter the microfossil preservation. - Limited access to deep stratigraphic sequences, restricting the study of deeper, older layers. 1.2 Subsurface or Drilled Cores and Cuttings- These are samples collected from boreholes or drilled wells, either as intact cores (continuous rock or sediment columns) or as fragmented cuttings generated during drilling. Application: Subsurface samples are crucial for studying deeper geological sequences, particularly in hydrocarbon exploration, paleoclimatic studies, and stratigraphy. Method: Cores: Long cylinders of rock or sediment extracted using coring tools during drilling. They preserve the stratigraphic integrity of the subsurface layers. Cuttings: Rock fragments obtained while drilling, typically collected at regular depth intervals. They provide information about the formations being drilled through. Advantages: - Access to deep, undisturbed sequences, essential for understanding buried geological layers and older rock units. - Cores offer continuous and stratigraphically preserved records. - Used in conjunction with downhole geophysical data for a comprehensive subsurface analysis. Disadvantages: - Expensive and time-consuming, requiring specialized drilling equipment. - Cuttings are often fragmented and disturbed, limiting GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 14 precise stratigraphic correlation. - The risk of contamination or loss of material when recovering subsurface samples. 2. Sampling Strategies The effectiveness of micropaleontological analysis relies on appropriate sampling strategies. The two main methods are: 2.1 Grab Sampling Definition: A quick and simple method in which a single sample is taken from a specific point or layer of interest. Commonly used for surface or shallow subsurface sampling. Method: - A small amount of sediment or rock is extracted from a site using tools such as scoops, shovels, or grabs (in marine settings). - In boreholes, grab sampling can involve retrieving small amounts of sediment or rock from a specific depth. Advantages: - Quick and easy to implement, ideal for exploratory studies or spot-checking specific horizons. - Minimal disturbance to the surrounding environment. - Suitable for a preliminary assessment of microfossil content and environmental conditions. Disadvantages: - Provides limited stratigraphic or spatial context, which can lead to an incomplete understanding of the site. - May miss microfossil assemblages that vary vertically or horizontally within the stratigraphy. - Not ideal for studying gradual changes over time or across facies. 2.2 Spot Sampling – GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 15 Definition: A method of collecting samples at specific intervals or depths within a defined area or section. It provides snapshots of different layers or horizons in an outcrop or core. - Method: - Samples are taken at regular or targeted intervals, such as every 10 cm in a core or at distinct stratigraphic breaks. - Used both for surface sampling (e.g., across a sedimentary section) and subsurface cores (e.g., from boreholes). Advantages: - Allows for more detailed vertical analysis of stratigraphic sequences and microfossil distribution. - Useful for biostratigraphy, as spot samples can be taken across key boundaries or transitions in the rock record. Disadvantages: - Still lacks the continuity of detailed sampling methods like channel sampling. - May miss fine-scale variations in microfossil assemblages between sampling points. 2.3 Channel Sampling – Definition: A more systematic and continuous sampling technique where a sample is collected across a continuous section of an outcrop, core, or stratigraphic unit. – Method: - A channel or trench is cut into the sediment or rock, and material is collected along the length of the channel. - This method can also be applied to cores by sampling continuously along a portion of the core length. Advantages: - Provides a continuous record of microfossil distribution and sedimentological changes over a defined interval. - Ideal for biostratigraphic studies, paleoenvironmental reconstructions, and identifying key stratigraphic boundaries. - Captures fine-scale variations in the microfossil GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 16 assemblages, providing a more complete stratigraphic profile. Disadvantages: - More time-consuming and labor-intensive compared to grab and spot sampling. - Requires careful planning and execution to avoid contamination or loss of material. - The larger volume of material collected may increase processing and storage requirements. 3. Pros and cons 4. Summary of Key Points - Outcrop or surface samples provide easy access to exposed stratigraphy but may be weathered or disturbed. - Subsurface cores and cuttings are essential for deep stratigraphic analysis, especially in hydrocarbon exploration, but are expensive and require specialized equipment. - Sampling strategies like grab sampling and spot sampling are effective for preliminary and targeted studies, while channel sampling provides the most detailed and continuous stratigraphic records. - The choice of sampling method depends on the research objectives, the geological context, and the availability of resources. These strategies form the basis for successful micropaleontological studies, providing crucial information on the stratigraphy, fossil content, and depositional history of geological formations. GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 17 Lecture 3 Foraminifera are widely used in micropaleontology due to their sensitivity to environmental changes, widespread distribution, and abundance in the fossil record. Their applications span multiple categories, including age dating, paleoenvironmental reconstructions, and paleoclimatic studies. Below is a detailed exploration of how foraminifera can be applied in different ways. --- 1. Individual Species or Taxon as Age or Paleoenvironment Indicators Certain species of foraminifera are known to thrive in specific environmental conditions or time periods, making them excellent biostratigraphic markers. Examples: - Index Fossils for Biostratigraphy: Genera like Globotruncana and Rotalipora are known as index fossils for the Late Cretaceous period. Their limited temporal ranges make them ideal for dating sedimentary layers. - Paleoenvironment Indicators: Ammonia tepida is commonly found in brackish water environments, signaling coastal and estuarine conditions. Its presence in fossil records suggests a nearshore, low-salinity paleoenvironment. Key Points: - Individual species can provide precise age constraints based on their known appearance and extinction events. Specific taxa are indicators of certain paleoenvironmental conditions, such as oxygen levels or water depth. 2. Entire Assemblage or Community as Environmental Indicators The diversity, abundance, and composition of foraminiferal assemblages can be used to infer broader paleoenvironmental conditions, such as water depth, salinity, or temperature. GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 18 Examples: - Benthic Foraminiferal Assemblages: The ratio of epifaunal (living on the seafloor) to infaunal (burrowing) foraminifera within a community can indicate oxygen levels in the seafloor sediments. A higher proportion of infaunal species, such as Bulimina, suggests low-oxygen, dysoxic conditions. Planktic Foraminiferal Assemblages: Assemblages of warm-water species like Globigerinoides ruber and cold-water species like Neogloboquadrina pachyderma can reveal past ocean temperatures and current systems. The presence of these species in deep-sea cores is used to reconstruct paleoclimates and ocean circulation patterns. Key Points: - Entire foraminiferal communities provide a more comprehensive view of environmental conditions, including temperature, salinity, and oxygen levels. Shifts in assemblages over stratigraphic intervals can indicate environmental change, such as transgressions or regressions in marine settings. 3. Shell (Test) Geochemistry as a Paleoclimate or Paleoenvironment Indicator The chemical composition of foraminiferal shells, particularly stable isotopes and trace elements can provide insights into past oceanographic and climatic conditions. Examples: - Oxygen Isotope Ratios (δ¹⁸O): The ratio of oxygen isotopes in foraminiferal shells reflects the temperature of the water in which the foraminifera lived, as well as ice volume. Higher δ¹⁸O values indicate colder periods with more ice volume (glacial periods), while lower values indicate warmer periods (interglacial periods). - This has been widely used in planktic GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 19 foraminifera like Globigerina bulloides to reconstruct Quaternary glacial- interglacial cycles. Carbon Isotope Ratios (δ¹³C): The carbon isotope composition of foraminifera reflects the global carbon cycle, including productivity and ocean circulation. Benthic foraminifera like Cibicidoides are often used to track deep-water circulation changes. Trace Elements (Mg/Ca Ratios): Magnesium to calcium ratios in foraminiferal shells provide a proxy for past ocean temperatures. This method is particularly useful for reconstructing sea surface temperatures in planktic species. Key Points: - Geochemical analyses of foraminiferal tests (shells) offer quantitative data on past temperature, salinity, ice volume, and carbon cycling. These methods allow for high-resolution reconstructions of paleoclimatic conditions, particularly in marine environments. 4. Test Preservation as a Paleo-pH and Environmental Condition Indicator The preservation state of foraminiferal shells can provide insights into paleo- pH conditions and sedimentary environments, as carbonate dissolution is influenced by the acidity of ocean waters. Examples: - Dissolution Indicators: Poorly preserved foraminiferal tests, characterized by dissolution features such as pitting and fragmentation, can indicate past episodes of ocean acidification or low carbonate saturation in deep waters. For example, shells of Globorotalia menardii found in poor condition in certain GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 20 deep-sea cores suggest more acidic conditions in the deep ocean during past warm intervals. Paleo-pH Reconstructions: By studying the relative abundance of species more resistant to dissolution (e.g., Orbulina universa), micropaleontologists can infer changes in ocean pH over time. This is important for understanding long-term shifts in ocean chemistry and carbonate saturation. Key Points: - The degree of shell preservation offers clues about past ocean acidity, which is linked to broader environmental changes, including volcanic activity, ocean circulation, and atmospheric CO₂ levels. Well-preserved assemblages suggest higher carbonate saturation, while poor preservation may point to acidification or corrosive deep waters. 5. Morphology and Abnormalities in Shells as Paleoenvironmental Indicators The shape and size of foraminiferal tests can reflect environmental stressors, such as pollution, temperature changes, or changes in nutrient levels. Abnormalities in test structure are often linked to environmental disturbances. Examples: - Morphological Changes: In stressed environments, such as areas with low oxygen or high pollution, foraminifera may exhibit deformed tests. For instance, abnormalities in Ammonia and Elphidium species have been linked to hypoxia in modern coastal environments, a condition which could similarly be inferred in fossil records. - Size Variability: The size of planktic foraminifera, such as Globigerina, can vary with water temperature and nutrient availability. Larger sizes are often associated with warmer, nutrient-rich conditions, while smaller sizes may indicate nutrient stress or colder conditions. - Test Thickness and Shell Abnormalities: The GS 421 Paleontology Micropalaeontology Jahnavi Punekar  P a g e | 21 thickness of foraminiferal shells can vary in response to changes in carbonate ion concentration. Thicker shells in species like Globigerinella siphonifera may indicate periods of higher carbonate saturation, whereas thinner, malformed shells suggest environmental stressors, such as acidification. Key Points: - Morphological features, such as test size, thickness, and abnormalities, provide clues about the foraminiferal response to environmental stressors, including pollution, temperature fluctuations, and nutrient availability. - Abnormalities in fossilized foraminifera can signal past environmental disturbances, including pollution events or climate shifts. --- Summary of Key Applications of Foraminifera 1. Individual species like Globotruncana serve as biostratigraphic markers for specific time intervals and indicate particular environmental conditions. 2. Foraminiferal assemblages reveal broader paleoenvironmental conditions, such as oxygen levels, water depth, and temperature. 3. Geochemical analyses of foraminiferal tests provide quantitative data on paleotemperature, salinity, and ice volume. 4. Test preservation informs on paleo-pH and ocean chemistry, helping to reconstruct past ocean acidification events. 5. Morphology and abnormalities in foraminiferal shells offer insights into environmental stressors, including pollution and nutrient stress. Foraminifera, through their abundance, diversity, and sensitivity to environmental conditions, are invaluable tools for reconstructing past climates and environments across geologic time, contributing significantly to our understanding of Earth’s history. GS 421 Paleontology Micropalaeontology Jahnavi Punekar GS 421 Palaeontology “Micropalaeontology and Applications” Textbook: Micropaleontology Principles and Applications Saraswati and Srinivasan  INTRODUCTION Background Major groups of microfossils Sampling Processing Analysis Applications: Palaeoenvironmental Industrial  What are microfossils? Fossilized remains of micro-organisms or tiny hard parts of larger organisms. Plankton Benthic fauna Many different groups representing animals, protists, and a variety of algae.  What? Why? Microscopic fossils Need a microscope to see Probability of finding is pretty high – Most sediments contain microfossils! Abundant! –10 cm3 of sediment can yield over 10,000 individual specimens and over300 species Population studiespossible Can be recovered from small samples Grab-sampling, drill-cores etc. Global distribution: marine cosmopolitan microfossils!  Microfossils Microscopic shells- provide ages for thinner packets of sediment (as opposed to a dino femur) better time resolution Short generation time, fast evolving short species ranges; better time resolution Sensitive to ambient conditions- changes in morphology and/or ecology record slightest of environmental changes Cosmopolitan species reliable global correlations possible MICROFOSSILS TIME/DURATION (ABSOLUTE/RELATIVE DATING) BIO-GEO EVENT NATURE/IMPACT SPATIAL CONSTRAINT (FAUNAL ANALYSIS) (CORRELATION)  Classification Organic Walled Inorganic Walled q Acritarchs and prasinophytes q Calcareous nannoplankton: coccolithophores and discoasters q Dinoflagellates q Foraminifera q Chitinozoa q Radiozoa (Acantharia,Phaeodaria q Scolecodonts and Radiolaria) and Heliozoa q Spores and pollen q Diatoms q Silicoflagellates andchrysophytes ORGANIC WALLED  Acritarchs and Prasinophytes Achritarch: name coined by Evitt in 1963; means "of uncertain origin” Artificial group Any small (most are between 20-150 microns across), organic-walled microfossil which cannot be assigned to a natural group Algal affinities, probably the cysts of planktonic eukaryotic algae Derived from phytoplankton Oldest known Acritarchs from shales of Palaeoproterozoic (1900-1600 Ma) age in the former Soviet Union  Dinoflagellates Group of flagellate protists Marine/freshwater plankton Population distribution depends on temperature, salinity, or depth Photosynthetic/Mixotrophic Symbionts with coral reefs One of the largest groups of marine eukaryotes with a total of 2,294 living dinoflagellate species  Chitinozoa Large (50-2000 microns) flask-shaped palynomorphs Dark, almost opaque when viewed using a light microscope Chitinozoa first appear in the early Ordovician  Scolecodonts Jaw of a polychaete annelid (worms) Chitinous teeth + bristles Cambrian to recent Only marine polychaetes actually get preserved at all (why?)  Spores and pollen Swedish palynologist Von Post (1917): tree pollen preserved in peat for Quaternary climate Palynology (along with achrit. And chitino., all acid-resistant organic microfossils) Spores of bacteria, fungi, algae and protists rarely preserved Terrestrial plants: extremely resistant spores and pollen Spores : "lower plants" or cryptogams: pteridophytic vascular plants and bryophytes (mosses, liverworts and hornworts) Pollen : seed plants, both angioperms and gymnosperms - 15 µm INORGANIC WALLED  Calcareous nannoplankton: coccolithophores and discoasters Coccoliths are individual plates Nano scale Made of CaCO3 Varying degrees of preservation infossil record Contribute to “ooze s” and may eventually form “chalk” Coccospheres  Coccoliths formed within the cell in vesicles derived from the golgi body Vesicles fuse with the cell wall and the coccolith is exocytosed, incorporated in the coccosphere Either dispersed following death and disarticulation, or are shed continually Foraminifera  What are foraminifera??? Amoeboid protists- single celled Shell or test (preservation potential) : – Secrete CaCO3 – sediment particles – organic tests below CCD (e.g. forams of MarianaTrench) Have thin pseudopodia (like amoeba) spread out as a net to catch food Tiny- usually Ichthyostega --> Amphibia Gradualism : A feature gradually evolves (e.g. limbs are intermediate) Mosaic evolution: That evolutionary change takes place in some body parts or systems without simultaneous changes in other parts Another definition is the "evolution of characters at various rates both within and between species (limbs evolved faster than braincase, tail fin, tooth structure) eustheno- "strength" and -pteron "wing“ A genus of Class Sarcopterygii of bony fishes with sarco- “lobe” pteryx-“fins” Ichthyostega- primitive tetrapod Ikthus- “fish” stega- “roof”  Contents Species, Individual, Population, Gene Pool Evolution- to change – Theories of Evolution (4-5 theories) Lamarckism- inheritance of acquired traits Darwinism – Variation in traits – Limiting factors and struggle for existence – Natural Selection of “fittest” traits – Inheritance of these traits Mutation Theory Neo-Darwinism – Types of Evolution based on magnitude and time scales Microevolution Macroevolution – Types of Evolution based on process and resultant adaptation Divergent Convergent Parallel Coevolution  Divergent Evolution also known as adaptive radiation two or more species that share a common ancestor evolve and accumulate differences over time, leading to the development of distinct characteristics and adaptations when species become more dissimilar in response to different environmental pressures or ecological niches  Process: Divergent Evolution Homologous Organs Cause: Adaptive Radiation similar structure but different functions  Key points for divergent evolution Common Ancestry: Divergent evolution always begins with a common ancestor. Two or more species share a genetic heritage and certain traits due to their shared evolutionary history. Adaptation to Different Environments or Niches: Divergent evolution typically occurs when groups of organisms inhabit different environments or ecological niches. Each group faces unique selective pressures and challenges, which drive the evolution of distinct traits and adaptations. Accumulation of Differences: Over time, each lineage within the diverging group accumulates genetic and phenotypic differences. These differences can be in terms of morphology (physical characteristics), behavior, physiology, and genetics. Development of New Species: In some cases, the process of divergent evolution can lead to the formation of new species. When populations within a group become reproductively isolated from one another, they can no longer interbreed, and over time, genetic differences accumulate, ultimately resulting in the formation of separate species. Other Examples of Divergent Evolution Darwin's Finches: One of the classic examples of divergent evolution comes from the Galápagos Islands, where Charles Darwin observed a group of finches that had evolved different beak shapes and feeding behaviors to exploit various food sources on different islands. These adaptations allowed the finches to occupy distinct ecological niches. Mammalian Limbs: The limbs of mammals, including humans, horses, bats, and whales, share a common ancestry but have evolved divergently to serve different functions. For example, the forelimbs of a human, a bat, and a whale have adapted for grasping, flying, and swimming, respectively. African Rift Lakes Cichlids: In the African Rift Lakes, cichlid fish have undergone remarkable diversification. Different species of cichlids have evolved various body shapes, feeding strategies, and coloration patterns based on their habitats and dietary preferences within the lakes. (sympatric) Marsupial Mammals in Australia: Australia is known for its unique marsupial mammals, such as kangaroos, koalas, and wombats. These marsupials evolved divergently from their placental counterparts in other parts of the world, resulting in distinct adaptations and ecological roles.  Convergent Evolution describes the independent evolution of similar traits or characteristics in unrelated or distantly related species because different species have adapted to similar environmental or ecological conditions, even though they do not share a recent common ancestor results in analogous structures or functions in different organisms  Process: Analogous Convergent Organs Evolution Cause: Colonizing the same habitat similar function but different structure/origin  Key Points on Convergent evolution Independent Evolution: In convergent evolution, similar traits or features evolve independently in different lineages. This occurs because similar environmental pressures or ecological niches lead to the selection of similar traits. No Common Ancestry: Unlike divergent evolution, where species share a common ancestor and evolve different traits, species exhibiting convergent evolution do not share a recent common ancestor that possessed the similar trait in question. Functional Similarity: Convergent evolution often leads to the development of similar functions or adaptations in different species, even though the underlying genetic and structural mechanisms may be distinct.  Examples of Convergent Evolution Wings in Birds, Bats, and Insects: The development of wings for flight has occurred independently in birds, bats, and insects. While the wing structures and origins of flight are quite different in these groups (birds have feathers, bats have modified forelimbs, and insects have exoskeletal wing structures), the function of flight is similar. Echolocation in Bats and Dolphins: Bats and dolphins are distantly related species, yet both have evolved the ability to use echolocation for navigating and hunting in their respective environments. They emit high-frequency sounds and use the returning echoes to determine the location of objects or prey. Camera-Like Eyes in Octopuses and Vertebrates: Octopuses have highly developed camera-like eyes with a single lens, similar to the eyes of vertebrates like humans. This convergent evolution of sophisticated eyes allows both groups to perceive and react to their surroundings effectively. Thorns and Spines in Plants: Various unrelated plant species have independently evolved thorns, spines, or prickles as a defense mechanism against herbivores. These structures deter herbivores from consuming the plant's tissues, even though the plants themselves are not closely related. Gliding Adaptations in Sugar Gliders and Flying Squirrels: Sugar gliders, marsupial mammals native to Australia, and flying squirrels, placental mammals found in different parts of the world, have both evolved adaptations for gliding through the air. They possess specialized membranes that allow them to glide between trees in their respective habitats.  Parallel Evolution Parallel evolution is a specific subset of convergent evolution. It occurs when two or more closely related species that share a recent common ancestor independently evolve similar traits or characteristics due to similar environmental or ecological pressures. the similar traits arise in distinct lineages with a recent shared ancestry, rather than in unrelated or distantly related species  Key points for Parallel Evolution Shared Ancestry: In parallel evolution, the species exhibiting similar traits share a common ancestor that possessed the trait to some degree. However, the trait may have been relatively undeveloped or exhibited in a different form in the common ancestor. Independent Evolution: Despite their shared ancestry, these species independently evolve similar traits in response to similar selective pressures. This can involve genetic changes and adaptations that are specific to each lineage. Similar Traits: Parallel evolution results in the development of similar traits or adaptations in different lineages, often in response to comparable environmental or ecological conditions. These traits may serve the same function or purpose in each lineage.  Examples of Parallel Evolution Marsupial Mammals in Australia and Placental Mammals in Other Continents: In Australia, marsupial mammals such as the marsupial mole and the marsupial "mouse" evolved similar adaptations to their placental counterparts in other parts of the world. For example, the marsupial mole and the placental mole both have adaptations for burrowing, even though they are not closely related. Antifreeze Proteins in Fish: Certain fish species in both the Arctic and Antarctic regions have evolved antifreeze proteins that allow them to survive in extremely cold waters. These proteins independently evolved in response to the need to prevent ice crystals from forming in their bodies. Stick Insects: Stick insects (phasmids) are known for their remarkable camouflage. Similar forms of mimicry and camouflage have evolved independently in different lineages of stick insects, allowing them to blend into their respective environments. Gill Evolution in Cavefish: Cavefish from different caves and regions around the world have independently evolved adaptations for living in dark, subterranean environments. One common adaptation is the loss or reduction of eyesight and the development of enhanced sensory organs, such as taste buds and lateral line systems, to navigate and find prey in complete darkness.  Convergent vs Parallel Evolution These animals have evolved similar adaptations (mouth) for obtaining food because they occupy similar niches. What can you infer about their phylogeny from their geographic locations? THINK ABOUT IT YOURSELF  Coevolution Interactions between species can cause microevolution – Changes in the gene pool of one species can cause changes in the gene pool of the other The Red Queen Effect: organisms must constantly adapt, evolve, and proliferate – to gain reproductive advantage – to survive in an ever-evolving opposing organisms in an ever-changing environment Hypothesis explains two different phenomena: – the constant extinction rates – the advantage of sexual reproduction Can also be symbiotic coevolution – Angiosperms and insects (pollinators) – Corals and zooxanthellae – Rhizobium bacteria and legume root nodules “Now, here, you see, it takes all the running you can do, to keep in the same place.“ - Lewis Carroll  Coevolution the mutual and often reciprocal evolutionary changes in two or more species that interact closely with each other Reciprocal Evolution: Coevolution involves the reciprocal evolution of interacting species. Changes in one species can lead to changes in the other, and this reciprocal process continues as the two species influence each other's traits and behaviors. Diverse Interactions: Coevolution can occur in various ecological interactions, including: – Predator-Prey Interactions: As predators evolve better hunting strategies, prey species may evolve improved defenses. – Host-Parasite Interactions: Parasites may evolve ways to better exploit their hosts, while hosts evolve defenses to resist parasitism. – Mutualistic Relationships: In mutualistic interactions (e.g., pollination, mutualism between plants and pollinators), species may coevolve to enhance the benefits they receive from one another. – Competition: In competitive interactions, species may evolve traits or behaviors that allow them to outcompete one another.  Examples of Coevolution Predator-Prey Coevolution: – Cheetahs and gazelles: Cheetahs are fast runners, and their prey, gazelles, have evolved to be swift and agile to evade capture. This coevolutionary arms race has led to the development of speed and agility in both predator and prey. Host-Parasite Coevolution: – Host immune systems and pathogens: As pathogens evolve to evade the immune systems of their host species, hosts may develop new immune defenses. This ongoing coevolution is seen in the ever-changing relationships between hosts and pathogens, including bacteria and viruses. Mutualistic Coevolution: – Flowers and pollinators: Flowers have evolved various shapes, colors, and nectar rewards to attract pollinators like bees and butterflies. In response, pollinators have evolved traits that allow them to efficiently collect nectar and pollen from specific types of flowers. Plant-Herbivore Coevolution: – Milkweed plants and monarch butterflies: Monarch butterflies lay their eggs on milkweed plants, and the caterpillars feed on milkweed leaves. Milkweed plants have developed toxins that deter most herbivores, but monarch caterpillars have evolved resistance to these toxins. Ant-Plant Mutualism: – Certain plants have evolved specialized structures, such as hollow thorns, to house and protect ants. In return, ants defend the plants from herbivores.  Rates of Evolutionary Change G. G. Simpson: “Tempo & Mode in Evolution” (1944) applied principles of modern synthesis (e.g. population genetics) to fossil record macroevolution ≈ microevolution amplified Two ways to measure evolution → Phylogenetic rate Taxonomic rate  1) Phylogenetic Rate Rate of Morphological change rate of change of character or group of characters in a lineage Rate = Change/ Unit Time  Rates of Evolution of Single Characters Haldane (1949): macroevolutionary changes in the dimensions of fossils can be compared darwin = change in e / m.y. (ln x2 - ln x1 /change in t) Transformation : Since the difference between two natural logarithms is a dimensionless ratio, ANY trait may be measured in any unit. e.g. jaw length 34 mm to 56 mm over 12 my ln (34) = 3.526; ln (56) = 4.025 rate of change = ? Evolution of Equine Lineage  McFadden (1992): 408 specimens 26 ancestor - descendent pairs 4 characteristics of teeth General trend: pointy, narrow (leaf eater) → wide, flat (grazer) 26 X 4 = 104 estimates of evolutionary ∆ 0.05 - 0.1 darwins mainly positive, but also some reversals  Comparing Rates ∆ in size of Ceratopsids = 0.06 darwins ∆ in skeletal dimensions of Passer domesticus after intro. to N. Am. = 50 - 300 darwins artificial selection: 60,000 darwins! continuous fossil records show low rates, masking frequent advances & reversals  Concerns with this measurement characters evolve at different rates (mosaic evolution) rate of change is not constant through time conservative characters: general adaptations, don’t change much over time derived characters: specialized, rapid evolution  2) Taxonomic Rate Replacement of taxonomic “units” origination & extinction (cladogenesis) Quantified: (# taxa originate - # taxa extinct) / unit time Or just the inverse of the average duration of a species ie. Rate = (Age of species)-1  Taxonomic Rates Rate of Origination or Extinction = No. of new O or E taxa Time Interval Per Capita Rate of O or E = No. of new O or E taxa x 100 No. of taxa in a time interval of interest Normalized Per Capita Rate of O or E = No. of new O or E taxa x 100 No. of taxa x time interval  Speciation Evolutionary process by which populations evolve into new species Modes- Allopatric, Parapatric, Peripatric, Sympatric Process- Cladogenesis and Anagenesis  Other Terminologies: Speciation w.r.t. time Speciation: Evolutionary process of forming of a new species.. Gradual transformation Lineage splits From old to new species Two or more new species No change in diversity Increase in diversity PHYLETIC TRANSITION SPECIATION  Cladogenesis & Anagenesis Speciation at t1 & t2 a & c contemporary b goes extinct Cladogenesis: – Branching speciation Anagenesis: Speciation without branching (phyletic transition)  https://textimgs.s3.amazonaws.com/boundless-biology/figure-11-03-01.jpe#fixme http://www.bio.miami.edu/dana/pix/horse_anagenesis.jpg https://prophoto7journal.files.wordpress.com/2016/08/9768671_orig.jpg  Chronospecies Problem in the fossil record: taxonomy based on preserved morphological characteristics ONLY Can you separate anagenesis from cladogenesis?? Identification of many chronospecies Chronospecies: descendent recognized as separate spp. Taxonomic Pseudo- extinction :O ↑Phylogenetic Rate leads to ↑ Taxonomic Rate rapid rate of morphological change leads to high rate of taxonomic replacement morphology time  Species through Time Biologists: species and populations well-defined based on morphological, genetic, and geographic separation Paleontologists/Evolutionary biologists- species through geologic time as one species evolves into another, taxonomic boundaries must somewhere be crossed no convenient gaps between species through time- transitional forms and missing links: where do they belong? Paleontologists ENTIRELY have to rely on morpho- differences of hard parts/preserved material, geographic difference and their experience! LOTS of loopholes and “educated guesses”  Species through a Geologists Eye Behavioral, soft-part morphologic and genetic definition will just not work Only hard-parts or tracks-n-trails! Chronospecies: Species in context of time (ref. evolutionary lineages) Morphospecies: “a group of individuals that have some reliable characters distinguishing them from other species” (more of a compromise sigh..) Species concept will depend on sample size of fossils observed (few samples of a very variable species may result in “splitting” E.g. Triceratops!! 80 yrs of collecting, 30 species all in just two counties of Wyoming… turns out all were one species (male, female, old, juvenile..)  Time makes it Tricky TIME Subjectivity in defining species!! Modified from Simpson, 1961b “An evolutionary species is a lineage... Evolving separately from others and with Its own unitary evolutionary role and tendencies...” Fixes to the Time Problem? Time-gaps in fossil record can result in morphologically distinct remains being preserved and the intermediate forms not preserved (good and bad for the paleontologist) TIME MORPHO- TREND Fixes to the Time Problem? Another way around it is to assume that most evolutionary change happened rapidly after a speciation event.. (small populations from which new species emerge may never make it to the fossil record) S.E. TIME S.E. S.E. MORPHO- TREND Mass Extinctions Topic 14 Illustrations come from multiple “The Big Five” sources including my own Or Six creations Or Seven Used for teaching purposes only  TRIGGERS Ecosystem/ Accelerated Geochemica ✓ Extraterrestrial Impact Extinction l Rates Perturbatio ✓ Large scale Volcanism n ✓ Extreme Climate Shifts ✓ Global Tectonics Mass Extinctions ONGOING EXTINCTIONS ? Often Linked to Loss of A >70% Catastrophi species c Trigger MASS EXTINCTIONS THE K-PG MASS EXT. DECCAN VOLCANISM OCEAN ACIDIFICATION PROXIES AND PROBLEMS CONCLUSION  The “Big Five” Deccan volcanism + Chicxulub Impact ~66 Ma; 80% Greenhouse warming, nuclear winters Marine toxicity/acidification Terrestrial trophic collapse CAMP volcanism Greenhouse warming ~201 Ma; Possible marine acidification/dysoxia 76% Ma; ~252 Emeishan + Siberian Trap volcanism 95% Greenhouse warming Marine acidification ~370 Ma; 70% Land plants + Erosion Marine anoxia + Black shales ~440 Ma; 85% Orogeny (Caledonian/Acadian? Land plants? CO2 drawdown + Climate change Data: Raup and Sepkoski Glaciation and Sea Level Fall Number of Genera → MASS EXTINCTIONS THE K-PG MASS EXT. DECCAN VOLCANISM OCEAN ACIDIFICATION PROXIES AND PROBLEMS CONCLUSION Paleozoic Era: Stratigraphy the largest mass extinction in history wiped out approximately 90% of all marine animal species "explosion" in diversity of multicellular life appearance of almost all living animal phyla within a few millions of years  The Burgess shale Lagerstatten Burgess shale quarry was discovered by Alexander (Charles) Walcott in the early 1900s The diversity of Cambrian fossils there is due to a Lagerstatten Depositional environment: bottom of an algal reef  Burgess Shale Fauna Anomalocaris Cambrian Explosion Marella splendens Marella splendens Sponge Vauxia glacilenta Olenoides serratus  Other Cambrian life Trilobites – type of arthropod (“jointed feet”), major predator, swimmer (nekton) Archaeocyathids – related to sponges Inarticulate brachipods (“lamp shells”) End of the Cambrian mass extinction got rid of many trilobites and all archeocyaths; cause may be marine transgression  Ordovician Epoch – 443-488 Ma International Stages 443.7 Mass extinction-2 443 Two mass extinctions Hirnantian at the end-Ordovician Mass extinction-1 445 Rawtheyan 488 First major diversity of life followed by major mass extinction; What caused it? During the Ordovician continents of Laurentia, Baltica, Siberia Separated from the supercontinent Gondwana; Iapetus ocean narrows.  The Ordovician At this time, the area north of the tropics was almost entirely ocean, and most of the world's land was collected into the southern super- continent Gondwana. Throughout the Ordovician, Gondwana shifted towards the South Pole and much of it was submerged underwater. Early to Middle Ordovician: Mild climate, warm and humid weather Great Ordovician Biodiversity Event (GOBE) All but one group (Graptolites) attained highest diversity during the Ordovician The Ordovician is best known for the presence of its diverse marine invertebrates, including graptolites, trilobites, brachiopods, and the conodonts (early vertebrates). A typical marine community consisted of these animals, plus red and green algae, primitive fish, cephalopods, corals, crinoids, and gastropods. More recently, there has been found evidence of tetrahedral spores that are similar to those of primitive land plants, suggesting that plants invaded the land at this time.  “EXPLOSION in MARINE DIVERSITY” Adaptive radiation - not innovation Diversification to take advantage of new eco-niches Articulate brachiopods Bryozoans Graptolite Graptolites Conodonts Bivalve: Spirifer Conodont Echinoderms Rugosa corals Rugose coral Tabulate corals Trilobite Mollusks - nautiloids Bivalves Gastropods Trilobites  Ordovician life Graptolites (Graptolithnia) are creatures that made their first appearance in the Cambrian but are considered index fossils of the Ordovician Look like “rock writing” , hence their name Are hemichordates! Go extinct during Carboniferous First land “plants” land-based lichen or fungi as early as 1.1 by Conventionally, there is good evidence for liverwort- like plants during the Ordovician – no vascular tissue, so short plants, near water The presence of plants will alter not only atmosphere chemistry, but also the rate of weathering Colonization of Land by Plants and Animals First successful and abundant land vegetation in Devonian All major groups of fishes evolved by middle to late Devonian Ostracoderms: primitive jawless fishes covered in armor of bony plates; Evolved at end of Ordovician.  Diversification of Animals in Ordovician Shallow wager, shelf environment bottom dwellers and floaters, few active swimmers All major phyla present by Cambrian. First Chordates (Ostracoderms- jawless fishes) appear at end of Ordovician.  End of Ordovician extinction Second largest mass extinction (except for the end of Permian) 450 to 440 my 85% of marine species extinct Late Ordovician: Gondwana finally settled on the South Pole → massive glaciers formed → sea levels dropped → shallow seas drained. Mass extinctions that characterize the end of the Ordovician; 60% of all marine invertebrate genera and 25% of all families went extinct.  EXTINCTIONS: BRACHIOPODS Major mass extinctions (Ashgill crisis) with more than 150 out of 180 genera extinct TWO CRISES (1) early Hirnantian: 60%of genera extinct; most devastating for shallow water tropical & temperate faunas WHY? ONLY LOW DIVERSITY COSMOPOLITAN FAUNA in early Hirnantian: marks the spread of cold-water high latitude faunas related to global cooling (2) second extinction in middle to late Hirnantian (end of extraoridnarius zone). Deep as well as shallow water genera extinct. Recovery in early Silurian. 443.7 Mass extinction-2 Hirnantian Mass extinction-1 445 Rawtheyan  EXTINCTIONS: Graptolites Most severe mass extinction during late Ashgill crisis – Late Rawtheyan extinction : only a few species survived Extinction was relatively sudden and unexpected Hirnantian Onset of recovery ASHGILL Extinction event Rawtheyan  EXTINCTIONS: Conodonts Conodont extinction almost as severe as for Graptolites: 33 out of 38 species extinct Extinctions occurred in late Hirnantian (perseculptus zone) - during graptolite recovery Conodonts entirely disappeared in high latitudes (Gondwana) Recovery was rapid Conodont extinctions 33 of 38 species extinct During time of graptolite recovery Hirnantian ASHGILL Graptolite extinction event Rawtheyan  EXTINCTIONS: Trilobita First Ordovician trilobites mass known extinction from Cambrian in Trilobites (540Ma) – similar Reached to Brachiopods max diversity in Cambrian Two extinctions separated by phase of low diversity, Cosmopolitan, cold-water faunas. First Extinction: of 113 genera 71 survived (3-4 families extinct) Second Extinction: of 71 genera only 45 survived. At family level 10 of 11 extinct. Water Column Problem? Extinctions were selective: all pelagic trilobites extinct (agnostids, cyclopygids) and many shelf taxa. all groups with planktic larval stages extinct - no adult pelagic forms evolved ever again Phacops shallow water (endemic) species relatively unscathed  EXTINCTIONS: REEFS ORDOVICIAN & SILURIAN reefs consisted primarily of tabulate corals (colonial corals) and stromatolites About 70% went extinct - but this was less than in other mass extinctions when reefs were completely wiped out.  Ordovician Predators Conodonts Nautiloids Ostracoderms (aranapsids) Eurypterids (sea scorpions)  Eurypterida - “sea scorpions” Extinct Paleozoic group, lived in shallow water, brackish, lagoons, Reached more than 2 m length May have been amphibious, breathing air; May be ancestral to scorpions Suffered major Ord. Extinctions Record poorly known  MOLLUSCA - Nautiloidea Marine mollusc with straight, curved or coiled shell. Diverse in Ordovician, but not well known and conflicting records as to “major mass extinction” or “minor event” Extinctions had no effect on higher taxonomic orders  Extinctions Recovery 1st 2nd Late Ordovician Early Silurian reefs Ordovician (Hirnantian) Mass Extinction (marine) High burial of organic matter High productivity Glaciation Keller et al., EGU Conference Abstract, 2006 after Hammarlund et al., 2012  RECAP: THE ASHGILLIAN CRISIS Gondwana Onset Major SL Fall EXTINCTION moves to Climate Glaciation Reduction PULSE-1 south pole Cooling Gondwana Niches ACTIVE Water Deep Upwelling Enhanced Enhanced Column Circulation Nutrients Productivity Organic C Dysoxia? Water EXTINCTION Sudden Stagnation Column PULSE-2 SL Rise Circulation Poisoning GS 421 Palaeontology Lecture Notes Jahnavi Punekar End-Ordovician Mass Extinction Occurred about 450 to 440 million years ago, marking the second largest mass extinction event, responsible for wiping out 85% of marine species. Two distinct pulses of extinction occurred during this period. Ordovician Epoch (443-488 Ma) The Ordovician was characterized by diverse marine ecosystems. The land was mostly concentrated in the southern supercontinent Gondwana, which was moving towards the South Pole. Early and Middle Ordovician: mild climate with warm, humid conditions. Great Ordovician Biodiversity Event (GOBE): a significant diversification in marine life, with most marine invertebrates reaching peak diversity. Ordovician marine life: included graptolites, trilobites, brachiopods, conodonts, cephalopods, corals, crinoids, gastropods, and early vertebrates like conodonts. Triggering Factors of Extinction Glaciation and Sea-Level Fall: As Gondwana moved to the South Pole, massive glaciers formed, causing global cooling. Sea levels dropped drastically, leading to the draining of shallow seas, which were home to diverse marine life. Pulse 1 (Early Hirnantian): 60% of genera, especially those in tropical and temperate shallow waters, went extinct. Cold-water cosmopolitan fauna replaced tropical ecosystems during this cooling period. Pulse 2 (Late Hirnantian): Extinction affected both deep and shallow water species. Post-extinction, species recovery began in the early Silurian. Impacts on Marine Life Brachiopods: 1 GS 421 Palaeontology Lecture Notes Jahnavi Punekar Ashgill Crisis: More than 150 out of 180 genera went extinct. Shallow water faunas, especially tropical species, were most affected, leaving behind a low diversity of cold-water cosmopolitan fauna. Graptolites: Late Rawtheyan extinction: the most severe extinction during the Ordovician. Most species were wiped out, leading to a sharp decline. The extinction occurred unexpectedly, and recovery followed in the early Silurian. Conodonts: Conodont extinction paralleled the graptolites, with 33 out of 38 species going extinct. Conodonts disappeared in high latitudes, but the recovery was relatively rapid. Trilobites: Trilobites, a dominant group from the Cambrian, faced significant losses during the Ordovician extinction. First wave of extinction: 71 out of 113 genera survived. Second wave of extinction: of the surviving 71 genera, only 45 survived. This event marked the extinction of all pelagic trilobites. Reefs: Ordovician and Silurian reefs were primarily composed of tabulate corals and stromatolites. About 70% of reef organisms went extinct, though the impact was less severe than in other mass extinctions. Paleoenvironmental Changes End-Ordovician Climate Shifts: As glaciers expanded and sea levels fell, shallow marine ecosystems were destroyed, triggering the first extinction pulse. A sudden rise in sea levels following glaciation may have caused additional environmental stress, leading to the second pulse of extinction. This includes Circulation changes: Active 2 GS 421 Palaeontology Lecture Notes Jahnavi Punekar deep circulation, enhanced nutrient upwelling, and organic carbon burial may have contributed to marine anoxia and dysoxia, exacerbating extinction events. Stagnation and toxicity: The combination of reduced shallow marine habitats and stagnant, nutrient-poisoned water columns led to further biotic stress and extinctions. Key Lessons from the End-Ordovician Extinction Mass extinctions often result from a combination of global environmental changes and catastrophic events. In the case of the End-Ordovician, global cooling, sea-level fluctuations, and marine anoxia were primary factors. These events highlight the vulnerability of ecosystems to rapid environmental shifts, particularly in marine settings where most biodiversity resides. In the last five years, significant advancements have reshaped our understanding of the End- Ordovician mass extinction (445 Ma). While global cooling and glaciation were traditionally thought to be the primary causes, recent studies highlight additional, complex drivers behind this biodiversity crisis. Volcanism and Mercury Evidence: New research suggests that increased volcanism, as indicated by elevated mercury (Hg) concentrations in sedimentary records, may have triggered environmental shifts. These volcanic eruptions released large amounts of greenhouse gases, contributing to global warming before the onset of glaciation. Mercury anomalies have been linked to volcanic activity in South China and Laurentia, showing a strong correlation with extinction pulses Oceanic Anoxia and Euxinia: The expansion of euxinia (sulfidic, oxygen-poor waters) has emerged as a key factor, especially during the second extinction pulse. Fe-speciation and molybdenum concentration studies have revealed that these anoxic and euxinic conditions developed in the oceans, disrupting marine ecosystems and causing widespread loss of benthic (bottom-dwelling) and nektonic (swimming) organisms This "double whammy" of climate change and euxinia likely exacerbated the extinction event. 3 GS 421 Palaeontology Lecture Notes Jahnavi Punekar Multi-Causal Factors: Rather than being driven by a single factor, recent research highlights a coincidence of causes. Global cooling initially drove extinctions among tropical marine species, while habitat destruction, euxinia, and possibly ocean acidification followed, intensifying the crisis THIS SUMMARY FIGURE 4 GS 421 Palaeontology Lecture Notes Jahnavi Punekar 1. δ18O as a Palaeoclimate Proxy How δ18O works: Oxygen isotopes are a primary tool for reconstructing past climates. Oxygen has two main isotopes, 16O and 18O, with 16O being lighter and more common. During colder periods, more 16O is trapped in ice sheets, leaving oceans enriched in the heavier 18O isotope. This relationship is preserved in marine sediments, especially in carbonate shells of organisms like foraminifera. In the stratigraphic record, Positive δ18O excursion (higher values): Indicates colder global temperatures or increased ice volume, as heavier isotopes like 18O are more prevalent in the ocean waters. Negative δ18O excursion (lower values): Suggests warmer global climates with melting ice sheets, leading to the release of lighter isotopes (16O) back into the ocean. In the figure: The δ18O curve shows a positive excursion during the Hirnantian glaciation, which corresponds to cooler climates and ice growth during the Late Ordovician. 2. δ13C as a Palaeoproductivity Proxy How δ13C works: Carbon has two stable isotopes: 12C and 13C. The ratio between these isotopes (δ13C) in marine carbonates and organic matter reflects the balance between organic carbon burial (which preferentially removes 12C) and the release of carbon back into the atmosphere or ocean. Positive δ13C excursion (higher values): Indicates increased organic carbon burial, often associated with heightened biological productivity or large-scale burial of organic matter, leading to a drawdown of atmospheric CO2. Negative δ13C excursion (lower values): Could suggest reduced organic productivity or increased release of carbon from organic sources back into the ocean-atmosphere system. In the figure: The δ13C shows significant variation, with positive excursions likely linked to enhanced carbon burial during cooling periods, potentially driven by increased productivity or changes in carbon cycling associated with the extinction event. 3. δ34S as a Palaeoredox Proxy 5 GS 421 Palaeontology Lecture Notes Jahnavi Punekar How δ34S works: Sulfur isotopes, particularly δ34S, help reconstruct the redox state of ancient oceans. Sulfate-reducing bacteria preferentially use lighter isotopes of sulfur (32S) during anaerobic respiration, leaving seawater enriched in the heavier isotope (34S) under anoxic or euxinic (sulfidic) conditions. Positive δ34S excursion (higher values): Suggests enhanced sulfate reduction, often indicating anoxic or euxinic conditions in marine environments. Negative δ34S excursion (lower values): Can imply more oxygenated conditions, as less sulfate is used up by anaerobic bacteria, leading to less isotope fractionation. In the figure: The δ34S values show both positive and negative fluctuations. Positive excursions likely correspond to periods of widespread ocean anoxia and euxinia, particularly during the second extinction pulse. Summary of the Proxies in the Figure In this figure, the δ18O data suggest significant global cooling during the Hirnantian glaciation, which aligns with the positive excursion seen in the middle panel. The δ13C profile shows fluctuations that likely correspond to changes in ocean productivity and carbon burial, with positive excursions indicating increased burial during cooler periods. Lastly, the δ34S record reflects shifts in ocean redox conditions, with the positive spikes indicating increased sulfate reduction and anoxia, particularly during the second pulse of the Late Ordovician mass extinction. Together, these proxies depict a complex interaction of cooling, changes in marine productivity, and the spread of anoxic conditions, all of which contributed to the environmental stress driving the extinction. 6 Late Devonian Crisis Silurian – Devonian First global distribution of trilobites and brachiopods land masses moved closer, eliminating major barriers to migration Lower Devonian ammonoids appeared (shells form limestone deposits) Fishes diversify bivalves, crinoids and blastoid, echinoderms, graptolites Trilobites - most groups disappeared by the end- Devonian On land: trees and forests appear for the first time, so do insects. tetrapods evolve. Devonian seas dominated by brachiopods, (spiriferids) tabulate and rugose corals, which built large reefs, red algae contributed to reef building Devonian Silurian Marine Life Silurian Devonian oceans dominated by reef-builders: stromatoporoids and corals Tabulate corals Rugosa corals ("horn corals”) common from Ordovician to the Permian abundant in Middle Ordovician to Late Permian. Possibly evolved in Lower Cambrian - Some solitary rugosans reached 1m - Some species formed large colonies. Rhodophyta Reef builders! All major groups of fishes evolved by middle to late Devonian Colonization of Land by Plants and Animals First successful and abundant land vegetation in Devonian TERRESTRIAL SYSTEM Plants: early Devonian only small plants (