Week 6 - Mesozoic Flashcards
What are the key themes of the Mesozoic Era?
Mass extinctions, flood basalt volcanism, break-up of Pangaea, hydrocarbon resources, and global sea-level rise.
What are the major periods of the Mesozoic?
Triassic, Jurassic, and Cretaceous.
What major geological event marked the beginning of the Mesozoic?
The Permian-Triassic mass extinction (~250 Ma)
What percentage of species went extinct at the Permian-Triassic boundary?
Approximately 80-95%.
What is the Siberian Traps?
A large igneous province linked to the Permian-Triassic mass extinction.
What are the consequences of large igneous province intrusions?
Venting of thermogenic gases (methane, CO₂, halocarbons), which impact atmospheric composition.
What is an example of a modern fissure eruption similar to ancient large igneous provinces?
The Grindavik eruption in Iceland (2023-2024).
What major tectonic event occurred during the Mesozoic?
The break-up of Pangaea, leading to the formation of the Atlantic Ocean.
How did mid-ocean ridge spreading affect sea levels in the Cretaceous?
Faster spreading rates increased ridge volume, displacing ocean water onto continental margins and raising sea levels.
What happened to global sea levels from the Late Cretaceous to the Miocene?
Sea level dropped by ~300m due to reduced spreading rates.
What major evolutionary developments occurred in the Mesozoic?
The rise of dinosaurs, birds, and flowering plants.
What is the Jehol Biota?
A fossil site in China with well-preserved Early Cretaceous birds and flowering plants.
What fossil evidence suggests polar forests existed during the Mesozoic?
Coniferous forest fossils found in polar regions, indicating a high-CO₂ greenhouse climate.
What are the basic elements of petroleum geology?
Source rocks, reservoir rocks, seals, and migration pathways.
What are examples of hydrocarbon reservoir rocks in the UK?
Sherwood Sandstone and Bridport Sand Formation.
What is the significance of the Blue Lias Formation?
It contains organic-rich shales that act as source rocks for oil and gas.
How did tropical sea-surface temperatures in the Cretaceous compare to today?
Cretaceous temperatures were 28-32°C, slightly warmer than modern tropical temperatures (<30°C).
What marks the end of the Mesozoic?
The Cretaceous-Paleogene (K/Pg) mass extinction (~66 Ma), likely caused by an asteroid impact.
What fossil site preserves the K/Pg boundary?
The Umbria-Marche section in Italy.
What percentage of marine species went extinct during the Permian-Triassic mass extinction?
About 76% to 95%.
What was the dominant cause of the Permian-Triassic extinction?
Massive volcanic activity in the Siberian Traps, leading to climate and atmospheric disruptions.
How did biodiversity recover after the Permian-Triassic extinction?
Marine and continental diversity gradually increased, with the rise of dinosaurs, birds, and flowering plants.
What are typical index fossils for Jurassic marine biostratigraphy?
Ammonites, such as Aulacostephanus autissiodorensis and Kosmoceras duncani.
What was a key feature of Confuciusornis sanctus, a fossil from the Early Cretaceous?
It had feathers with a modern, branched structure, showing bird evolution.
How did the closure of the Tethys Ocean affect global paleogeography?
It altered ocean currents and contributed to major climatic shifts.
What did Beerling and Osborne (2002) suggest about atmospheric CO₂ levels in the Mesozoic?
CO₂ levels were at least double modern levels, supporting greenhouse conditions.
Why were polar forests in the Mesozoic unique?
They had to adapt to long summers of continuous sunlight and dark winters.
What role did the Wytch Farm oil field play in the UK?
It is the largest onshore oil field in Europe, formed through regional tectonic processes.
What is the importance of the Bridport Sand Formation in the Wessex Basin?
It serves as a key hydrocarbon reservoir rock.
What gases were released in the Siberian trap eruptions and how did they impact the environment?
Methane, carbon dioxide, halocarbons (e.g., chlorofluorocarbons).
They contributed to climate change, ocean acidification, and atmospheric disruptions.
What were the major climatic zones in the Triassic?
Arid/semi-arid (beige) and humid (green) regions.
What is a ventifact, and what does it indicate?
A rock shaped by wind erosion, often with ‘desert varnish,’ evidence of arid conditions.
What was the climate like in the Early Jurassic (~190 Ma)?
A mix of arid and humid zones, with extensive marine environments.
What was the Central Atlantic Magmatic Province (CAMP)?
A large flood basalt province associated with the early break-up of Pangaea.
How did the break-up of Pangaea affect global sea levels?
It led to high sea levels due to increased mid-ocean ridge spreading.
How did the length and speed of mid-ocean ridge spreading influence sea levels?
Faster spreading meant more new crust, displacing ocean water onto continental margins.
