Historical Geology final

Mechanisms of the End-Permian mass extinction

The end permian extinction=252 Ma, and largest in history

• Massive volcanism

• Global warming (8-10 celcius increase)

• ocean anoxia

• ocean acidification: dissolved CO2, lowered the pH and harmed the CaCO3 organisms

• Methane release: destabilized methane hydrates

• Destructive wildfires: charcoal evidence

• Ozone destruction: increased UV radiation stress

Which didn’t have a meteor impact?

• end of the Permian- volcanism/climate stress

• late-devonian: environmental stresses

• end-triassic: central atlantic magmatic province volcanism

Major trends in paleozoic plants

• ordovician: first land plants(non vascular, moss)

• Silurian: first vascular plants

• devonian: first forests (lycopsids, ferns, progymnosperms)

• carboniferous: huge coal-swamp forests, dominance of lycopsids and ferns

• permian: expansion of gynosperms (drier climate seed favored plants)

Timing of Vertebrate expansion onto land

• earliest tetrapods appear in late devonian (360 Ma)

• full terrestrial ecosystems develop in Carboniferous

NEWARK supergroup that tell us their sediments were deposited in a river

• cross-bedding

• ripple marks

• channel-fill geometry

• mudcracks at floodplains

• conglomerates+ sandstones with directional flow structures

NEWARK supergroup that tell us their sediments were deposited in a lake

• varves

• fine-laminated mudstones

• fish fossils

• desiccation cracks at lake margins

Types of fossils in the Newark Supergroup

• footprints/trace fossils

• fish fossils

• plant impressions

• insects

Why are skeletal body fossils rare?

• oxidizing conditions in lake/rift environments oxidize bone

• high sediment reworking in rivers destroys shells and bones

• acidic lake waters in some rift systems dissolve calcium phosphate

• poor preservation potential in coarse fluvial sediments

Cretaceous- Early Paleogene+Early life

Role of Iridium in discovering the K-Pg impact

• Iridium is rare on Earth but abundant in meteorites.
  
  

• Globally distributed iridium spike at the K-Pg boundary triggered the impact hypothesis (Alvarez et al., 1980).
  
  

• Coincides with shocked quartz, microtektites, and the Chicxulub crater.