4 FOSSIL FORMATION AND STRATIGRAPHY

Question 1

Trace fossils

Answer 1

1. Tracks, footprints, burrows or scratches from organism left in sediment
2. Marks are buried and become rock
3. No body shape or organic material

Question 2

Index fossil

Answer 2

1. It is distinct
2. Globally widespread
3. Abundant
4. Limited to a particular geological time
5. Robust and preserves well

Question 3

The significance of index fossils in generating a geological timescale

Answer 3

• Their presence indicates widespread environmental changes, such as mass extinctions
• Limited life span is relatively dated to create a scale, which can be matched up with, and compared to, other fossils to define geological periods of time

Question 4

Relative dating

Answer 4

Determining relative order of events without exact age

Question 5

Absolute dating

Answer 5

Determining specific age through methods eg. Radiocarbon dating, uses igneous rocks and isotopes (rates of decay = time of creation)

Question 6

Superposition

Answer 6

Idea that undisturbed layers of rock have the youngest layer on top and oldest on the bottom

Question 7

Uniformitarianism

Answer 7

Geological events of the past occurred in the same way, at the same rate, and by the same natural processes as they do today.
eg fossilization, erosion, deposition, volcanism, evolution, and oceanic and climate events.

Question 8

Permineralization

Answer 8

• Fossilization process involving minerals transported by water
• Occurs when minerals fill in all open spaces of an organism or organic tissue
• Mineral deposits form internal casts within these spaces

Question 9

Mass extinction events (Cretaceous)

Answer 9

• 66 MA
• Cretaceous-Paleogene extinction event wiped out the dinosaurs, along with 60-76% of all life on Earth.
• Deccan Trap
• A widely accepted theory suggests that an asteroid impact occurred in the Yucatán Peninsula in Mexico, causing the extinction event.
• The impact would have released a large amount of debris into the atmosphere, leading to a drop in global temperatures.
• Localized effects of the impact may have included fires, earthquakes, tsunamis, and acid rain.

Question 10

Mass extinction events (PERMIAN-TRIASSIC EXTINCTION)

Answer 10

• 252 MA
• The Permian-Triassic was the deadliest extinction in history: 96% of all life perished. Permian strata abundant in fossils
• Scientist believe that volcanic activity in Siberia put massive amounts of carbon dioxide into the atmosphere.
• Bacteria that thrive on CO2 began producing methane.
• Large quantities of both gases warmed the planet and oceans, making acidic rain , creating a highly toxic environment for life.

Question 11

ORDOVICIAN-SILURIAN EXTINCTION

Answer 11

• 440 MILLION YEARS AGO (MA)
• Since most fauna was marine at the time, 86% of life was lost.
• Abundant plant life removed carbon dioxide (CO2) from the air, causing global cooling and glacier formation.
• This led to a drop in sea levels, reducing habitat.
• Later came global warming and sea level rising again.
• Creatures that had adapted to the cooler climate were unable to survive the increased temperature.

Question 12

LATE DEVONIAN
EXTINCTION

Answer 12

• 365 MA
• About 75% of life died off during this period.
• One theory suggests that land plants developed deep roots, releasing an abundance of nutrients into the oceans that fed algae. Because of this, algae blooms consumed vast amounts of oxygen (O2) in the oceans, suffocating many species.