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Quaternary Processes and Environments - Coggle Diagram
Quaternary Processes and Environments
Geological timescales
INTIMATE Event Stratigraphy
Saalian glaciation -> Eemian interglacial -> Weichselian glaciation (LGP) -> Bolling-Allerod -> Younger Dryas -> Holocene warming
Holocene Climatic Optimum
Mid-Pleistocene Transition
1.25mya - 700kya
Transition from 41,000yr G-IG cycles driven by obliquity to 100,000yr cycles (eccentricity)
During this transition period, both cycles overlapped and glacial periods became more severe/of higher amplitudes
Post-MPT, larger ice sheets -> sustained by albedo feedback -> pattern of longer-lasting glacials and shorter IGs
Contextualising current temp changes
Eemian interglacial (130-115kya)
Temps 1-2degreesC warmer than today
Sea levels 6-9m higher than today
Greenland ice sheet melting contributed 1-4m of this
Temperate forests dominated and expanded into former tundra areas
Marine sediments show increased biological productivity, and warmer SSTs -> suggests strong AMOC
Quaternary/post-glacial landforms -> inform past environments
Kames and kettle-holes
Eskers
BRITICE British-Irish Ice Sheet extent
Human activity
The Amazon
13-8kya -> regionally interconnected by 2kya
Regional settlement patterns with site size hierarchy (i.e. capital -> suburbs) evident in ADE waste sites (Roosevelt, 2013, studied nucleated settlement pattern over 12km)
collective organisation
Evidence by Amazonian Dark Earth soils formed from agricultural waste
Huge difference in fertility to unconsolidated Amazonian upland soils
ADE formation assoc with agri and therefore tree cropping -> secondary forests only regrow on fertile soils i.e. ADE soils -> ADE forests
High-capacity but high-risk carbon store as highly vulnerable to wildfires
Carbon storage of ADE forests comes from their below-ground biomass, versus coming from the complexity and maturity of vegetation in old growth forests
Schmidt et al.’s (2023) sample transects in the Amazon’s Upper Xingu region show ten-fold increase in key soil nutrients like potassium and magnesium, between ADE soils and background geology
previous research focus on N.American palaeocultures as Amazon though to be impenetrable ecological barrier (Roosevelt et al., 1996)
People crossed the Bering Strait into America, thought to have travelled down the Americas via the Andean chain, but stopped at the Amazon
This would have been 13kya, so pre-Holocene, but the Amazon was still in rainforest climate tolerances despite being 5degreesC colder (Colinvaux et al., 1996)
colonial assumption that the Amazon was a 'virgin' wilderness (Smith, 1980)
distinct South American palaeocultures (evidence in tools only found regionally)
Changes in vegetation patterning via preferential cultivation (Levis et al., 2017)
Over half of Amazon rainforest is made up of hyperdominant species (even when including old growth parts)
domesticated plant species are 5 x more likely to be hyperdominant than non-domesticated ones
Land bridges
Doggerland
Existence traced back to LGM (approx 26-19kya) when sea levels were 120m lower
Migration route despite gradual sea level rise during deglaciation into Holocene
Laurentide and Fennoscandian ice sheets melting -> gradual submergence of Doggerland. Wetlands in Early Holocene, islands by 8kya, final submergence accelerated by Storegga Slide tsunami approx 6.5kya
Human settlement Britain at start of Holocene, prev not consistent. Agri Rev 6kya (hunter-gatherers -> farmers)
MIS 12 in Britain
Hominims emerged about 300kya
Neanderthals present during the Eemian
G-IG cycles forced evolutionary adaptability
Proxies
Sediments
Lead-210 dating for recent sediments
14C radiocarbon dating for organic sediments
Age-depth modelling
Relies on radioactivity decay functions
To account for error, corrected to calibration curves formed from other proxies
IntCal20
MarineCal20
SHCal20
Coral reefs
Lake sediments
Annual varves
Tephrochronology
Speleothems
Cave in China?
Palaeoecology
Diatoms
Chironomids
Pollen
Other plant macrofossils
Ice cores (see age-depth modelling)
Greenland leads the inverse change in Antarctica by ~200yrs
Methane concentrations for validation as 10yr atmos life
Climate forcings
Radiative forcing
Orbital forcing
Milankovitch cycles
Precession
Obliquity
Eccentricity
'Pacemaker of the Ice Ages' (Hays, Imbrie and Shackleton, 1976) i.e. timing not amplitude
Feedbacks
Ocean circulation
AMOC shutdown - Heinrich events
Younger Dryas thought to be triggered by Laurentide drainage into N.Atlantic -> AMOC shutdown
2 to 6 degreesC temp decr in NHemi over just a few decades
Animal activity changes
Death of megafauna
