ERTH 16 (Mar11)

Typed

The Ordovician Environment

Could earth have had a ring??

Earth had a ring 466 MYA, impact craters found around earth that were made around thes ame time could be linked to debris falling form a ring a, new study suggest.

Temp & Climate

WHy care? becasue cold water hlds more gas inside, if you take a can of pop and heat it it will degas much faster, so cold holds it lnger. As life is in the ocean, the amount of oxygen in that ocean is gonna be held by cold water

The Great Ordovician Biodiversity Event

The GOBE is the most significant increase in marine biodiversity of the Phanerozoic

The GOBE laid the foundation for present-day biodiversity levels

• we are moving to a more familiar climate

This event postdates the Cambrian explosion by 40-50 Million years!

The sea floor is starting to look much more familiar

Three large phases

Phase 1: Plankton

Plankton are organisms that live in the water column but cannot freely swim

The timing of exactly when this kicked off is debated

We don’t really see modern types of plankton show up until much later BUT we do see lots of examples of other types of Plankton in Ordovician records

Phase 2: Benthic Communities

Benthic means organisms that live on the seafloor

While exact timings are tough the benthic phase of the GOBE came after the plankton phase

Phase 3: Reefs

Reefs are biologically produced calcium carbonate structures with some relief above the seafloor

While exact timings are tough the benthic phase of the GOBE came after the plankton phase

Other drivers of GOBE?

Perhaps changes in weathering regimes shifted nutrient availability?

Perhaps an expansion of habitats through sea level rise (transgression) increased biodiversity

And diversity driven by increased oxygen due to cooling ocean temperatures

if we have sea levels rising, there the current sea life will have to adapt to new conditions, potentially leading to shifts in species composition and the emergence of new environment for them to live, at this time there was much less glacial ice cover, which may have contributed to warmer ocean temperatures and further facilitated the proliferation of diverse marine species.

The key thing is that the GOBE is the greatest rise in biodiversity that we see in the fossil record

However, it’s pace and whether it was continuous or pulsed remains debated\ And it’s ultimate drivers also remain debated

GOBE vs Cambrian

Life in the Gobe resembled current like much more than Cambrian

Cambrian is more of a event, while the the GOBE happened in stages

The Hirnantian Glaciation

A drastic temp drop at the end of the Ordovician

The Hirnantian Glaciation is a glacial interval which is evidenced to have lasted ≈500,000 years

This was a regional NOT global glaciation

This was part of a longer term cooling trend

evidince?

• Sea level fall globally and the slight expansion of sea water in warm temps

• glacial rocks are found in fine grain material

Large glaicl drop stones found aorund high equator (not quite there)

Sealevel fall would have limited habitats

Sealevel fall and global cooling would have changed marine chemistry and ocean circulation

This ultimately led to the LATE ORDOVICIAN MASS EXTINCTION

The Late Ordovician Mass Extinction

What is a mass extinction?

• A mass extinction is an interval of rapid biodiversity loss where at least 75% of species go extinct within a short interval of time.

The Late Ordovician Mass Extinction

2 Phases: 1st Phase global cooling

Cooling temperatures would have driven sea level fall

This would have impacted available habitats, water chemistry and ocean circulation

These factors drove many species to die off.

Rapid temperature changes would have also impacted fauna that began to adapt to cold temperatures

This would have impacted available habitats, water chemistry and ocean circulation • These factors drove many species to die off.

In total from both phases: 85% of marine species, ≈50% of genera and 26% of all families

Its the change that’s important, rapid change is quite harmful, since evolution takes a very long long time

The Rise of Land Plants

Living on land has much more challenges pertaining to weather, climate, reproduction, Harmful UV, and the need for structural support.

Drought, unlikein the water trestial plants generate stomata, which creates GAS EXCHANGE, water fills the stmata and this is where PHOTOSYTHIESES happens

• Drought, unlike in aquatic environments, presents unique challenges for terrestrial plants, which generate stomata for gas exchange. Water fills the stomata, enabling photosynthesis to occur effectively, as it is essential for the plant's survival and growth in a land-based habitat.

geo record of land plants, we see lots of plant SPORES, then full plants, then full forests all about 40my appart

KAi

Exam Information

• Final Exam Date & Time: April 25 at 9 AM for 2 hours

• Important Note: No opportunities to change the exam date or time will be allowed; students are advised not to request changes.

Last Quiz Review

• Quiz Content Overview:

  • The immediate post-snowball Earth ocean is characterized by:

    • A freshwater surface layer overlying deep salt water.

    • Stratification may have lasted from thousands to tens of thousands of years.

  • Schuron Negative Carbonaceous Excursion:

    • Occurred around 574 to 567 million years ago.

  • Evidence for increasing oxygen levels during the Ediacaran:

    • Identified through distinct patterns in brain records of trace elements.

    • Overall climate during the Ediacaran was generally warm with large inland seas.

  • Reox Sensitive Elements:

    • Elements such as rhenium, uranium, chromium, and molybdenum used to reconstruct ancient marine oxygen levels.

    • Their presence depends on seawater conditions (oxygenated vs. anoxic).

  • Snowball Earth Hypothesis:

    • Proposed that the Earth was almost entirely ice-covered at times.

  • Biakirid Biota:

    • Organisms like Rhangia and Chiracanthium are noted as appearing immediately after the last glaciation.

    • A gap of approximately 40 years separates the end of glaciation from the appearance of these organisms.

  • Ice-Level Feedback Mechanism:

    • As ice sheets expand, they reflect more sunlight, causing further cooling and further ice expansion.

  • Deposits from Snowball Earth Events:

    • Suggest formation in warm, shallow waters, leading to significant consumption of atmospheric CO2.

  • Angular Rocks in Marine Sediments:

    • Evidence supports the processes of icebergs and glacial activity dropping sediment as they melt, notably at low ocean levels.

Glacial Lake Harlan - Plume World Hypothesis

• Represents freshwater accumulation during melting phases of Snowball Earth ice.

• Hypothesizes that early organisms thrived in this freshwater environment before flooding into the oceans.

Transition from Snowball Earth to the Phanerozoic

• Marked the beginning of the Bauerzoic and the Paleozoic Era.

• Cambrian Explosion:

  • Period where significant evolutionary advancements occurred, leading to diverse animal life forms and complex ecosystems.

  • Debate exists whether this explosion reflects an increase in life or simply an increase in fossil preservation.

Fossilization Processes

• Preservation Conditions:

  • Hard parts of organisms are better preserved than soft parts, affecting our understanding of ancient life.

  • Fossilization is biased toward species with larger populations and those that thrive in sedimentary environments.

• Index Fossils:

  • Used to define specific time periods in geological history since they have short-lived ranges and widespread existence.

• Precambrian vs. Phanerozoic:

  • Difficult to use fossils for dating in the Precambrian compared to the Phanerozoic where fossil evidence is more abundant.

Great Ordovician Biodiversity Event (GOBE)

• Significantly increased marine biodiversity, marked by an evolution of multiple organisms.

• Phases of GOBE:

  • 1. Planktonic Phase: Dominated by drifting microbes in the water column.

  • 2. Benthic Phase: Expansion of bottom-dwelling organisms like brachiopods and echinoderms.

  • 3. Reef Phase: Emergence of reef ecosystems fostering diverse marine life.

• Different environmental conditions and oxygen levels played a role in these phases.

Late Ordovician Mass Extinction

• Defined as the first major mass extinction event, resulting in a significant loss of marine species (up to 85%).

• Causes:

  • Cooling temperatures leading to sea level fall, impacting habitats and survival of species.

  • Associated with global igneous events contributing to shifts in climate and habitats.

The Rise of Terrestrial Plants

• Transition from aquatic to terrestrial ecosystems presented challenges:

  • Required adaptations to conserve moisture, support structures, and overcome increased sunlight exposure.

• Innovations for Terrestrial Growth:

  • Development of lignin, allowing plants to grow taller and more resilient.

  • Evolution of root systems and mutualistic relationships with fungi (mycorrhizae) for nutrient uptake.

• Geologic Record of Plant Evolution:

  • Plant spores appeared around 450 million years ago, marking significant steps toward terrestrial life.

PDF Summary

Lecture Overview

Course: ERTH 1009/1011Lecture Title: The Ordovician and the Rise of Land PlantsInstructor: Peter CrockfordTerm: Winter 2025

• Lecturer: Elizabeth (TA for 1011)

• Class will cover mid-term results and answers, useful for final exam preparation.

Mid-term Information

• Marks available on Brightspace for both 1011 and 1009 (apologies for the delay).

• Average mark for the class: Approximately 65%.

• Students with unexpected marks should contact TAs for revision discussion.

• Final exam format will mirror that of the mid-term, but it will be longer.

Final Exam Details

• Date: April 25

• Time: 9 AM

• Duration: 2 hours

• Format: 120 multiple choice and True/False questions

Quiz Questions Summary for 1011

Key Quiz Items (Quiz 6)

• Post-Snowball Earth ocean: Freshwater surface layer overlying a deep salty layer.

• Shuram negative carbon isotope excursion: Occurred 574-567 Ma.

• Evidence of Ediacaran oxygen levels: Marine trace element patterns.

• Ediacaran climate: Characterized by warmth and extensive inland seas.

• Redox sensitive elements (Re, U, Cr, Mo): Used to infer ancient marine oxygen levels.

• Snowball Earth hypothesis: Earth was likely covered in ice from pole to equator.

• Ediacaran biota appearance: Not immediately post-Snowball Earth.

• Ice-albedo feedback: Expanding ice sheets reflect more sunlight, promoting cooling.

• Cap carbonate rocks: Indicative of warm shallow water formation after glaciation.

• Ice-rafted dropstones: Evidence of icebergs depositing rocks.

• Volcanic activity during Snowball Earth: Continued to emit CO2.

• Glacial Lake Harland: Freshwater body during Snowball Earth’s melting.

Pleistocene Overview

Age Divisions

• Calabrian: 1.8 to 0.774 Ma

• Chibanian: 0.774 to 0.129 Ma

• Holocene: Divided into Greenlandian, Northgrippian, and Meghalayan ages.

The Cambrian Explosion

• Marks the emergence of most major animal groups in the sedimentary record.

• Also referred to as Cambrian Radiation or Cambrian Diversification.

Taphonomy and Fossil Record

Key Concepts

• Taphonomy: Study of how living organisms become fossils.

• Preservation potential: Hard parts (bones, shells) preserve better than soft tissues.

• The likelihood of fossilization depends on physiology, behavior, and geochemical conditions.

Index Fossils and Geologic Time

Examples of Index Fossils

• Cenozoic Era: Pecten gibbus, Calyptraphorus velatus.

• Mesozoic Era: Scaphites hippocrepis, Perisphinctes tiziani.

• Paleozoic Era: Mucrospirifer mucronatus, Palmatolepus unicornis.

Trace Fossils

• Ichnofossils represent evidence of an organism's presence without physical remains.

The Great Ordovician Biodiversity Event (GOBE)

Overview

• Represents the most significant increase in marine biodiversity during the Phanerozoic era, occurring 40-50 million years post-Cambrian explosion.

GOBE Phases

Phase 1: Plankton

• Included Chitinozoa, Acritarchs, and Graptolites.

Phase 2: Benthic Communities

• Included Brachiopods and Echinoderms.

Phase 3: Reef Development

• Included Bryozoans, Sponges, and Coral.

Drivers of GOBE

• Possible causes include shifts in nutrient availability and habitat expansion due to sea-level rise, alongside increased oxygen levels from cooling ocean temperatures.

The Hirnantian Glaciation

Characteristics

• Lasted about 500,000 years; considered a regional glaciation.

• Part of a long-term cooling trend affecting habitats and marine biodiversity.

The Late Ordovician Mass Extinction

Causes

• Factors included cooling temperatures affecting habitats and changing ocean circulation.

• Resulted in the extinction of approximately 85% of marine species.

• Two phases: global cooling and subsequent global warming.

The Rise of Land Plants

Innovations for Terrestrial Life

• Adaptations to harmful UV light and drought included the development of pigments and stomata.

• Nutrient acquisition strategies involved symbiotic relationships with fungi and the evolution of roots.

• Lignin: Key structural compound enabling plants to support themselves on land.

The Geologic Record of Land Plants

• First forests dated at approximately 390 million years ago in Gilboa, NY.

Summary of Key Terms

• Coral, Chitinozoa, Stromatoporid, Bryozoan, GOBE, Regression, Transgression, Graptolite, Rise of Land Plants, Ordovician, Silurian, Devonian, Hirnantian, Signor Lipps, Lignin, Mycorrhizal Fungi.

Example Questions for Review

• How does GOBE relate to temperature as a major atmospheric gas?

• What is marine transgression, and how does it affect biodiversity?

• Why does regression limit habitats for marine organisms?

• When did plants first colonize land?

• What is a stomata, and how does it help terrestrial plants?