Lecture 22: Quaternary Interglacials - Analogues? Flashcards
Which milankovitch cycle has dominated the glacial-interglacial cycles throughout most of the quaternary?
Obliquity
What milankovitch cycle has started to dominate the quaternary period in the most recent 1 million years?
Eccentricity
What has the transition from the obliquity to the eccentricity cycle meant for the occurrence of glacial and interglacial periods?
The glacial-interglacial cycle has become much more pronounced and clear
What are the names for the last interglacial?
Ipswichian and Eemian
What MIS is the last interglacial?
MIS 5
How many sub stages are there within MIS 5?
5
Which sub stage within MIS 5 is most closely studied for information about the last interglacial and why?
MIS 5e because it is the period when the last interglacial was most intense
Who was James Geikie?
Scottish geologist
What did James Geikie’s 1872 book consist of?
the organic deposits and Palaeolithic remains which he found in glacial tills and moraines he believed could not have occurred after tha last glacial period because there were glacial deposits on top indicating that another glacial period occurred after. Instead he claimed that this must have occurred before in a period which he called an interglacial
Who was Pieter Harting?
Dutch biologist in the late 19th century
What did Pieter Harting study and where?
Boreholes near Amersfoort in Netherlands
What did Pieter Harting find in the boreholes and what did he believe they were an indication of?
Marine sediments and shells of Mediterranean species which he believed were an indication of a previously warmer climate with higher sea levels
What did Pieter Harting name the period which he observed from boreholes? what would this later become?
Systeme Eemien - this would later become the widely recognised name for the last interglacial
Why does evidence for the last interglacial within Britain not come from peat and lake cores?
Because they normally do not stretch back far enough
What type of record does evidence from the last interglacial within Britain come from?
Archaeological and sediment record
What sort of site was analysed for the archaeological record?
Coastal/inland caves
What sort of evidence came from the sediment record in Britain?
River terraces and raised beaches
Where part of Britain does evidence for the last interglacial come from? why?
Southern parts because records further north were destroyed during last glacial maximum
What are some of the most famous sites for evidence for the last interglacial within Britain?
Bobbitshole (near Ipswich), Trafalgar square, Joint Mitnor Cave
How do river terraces provide evidence of the geological past?
In glacial and interglacial periods, river respond in certain ways that can either result in incision or aggradation. The deposits from that period can then be analysed and use the law of superposition, to reconstruct different periods
How do raised beaches and their deposits provide evidence of the geological past?
The deposits can be used to determine what sea level was at the time by dating the sediments. The sea level is a good indication of whether it is an interglacial or glacial period
What rivers contain evidence of previous river terraces?
Thames and Orwell
What areas contain evidence of previous raised beaches?
Saunton and Westward Ho!, Portland Bill, Hope’s Nose
How do caves contain evidence of geological past?
They contain evidence of many fauna such as hippopotamus, elephants and wild boars
What are some areas which contain caves which are used to analyse the past?
Joint Mitnor, Tornewton and Victoria Cave
Describe the Bobbits Hole UK type site? (type of record, depth, characteristics)
Organic rich mud that is 3.5m deep and banded by river terrace deposits from MIS 4 and MIS 6 above and below this mud layer
What was the Bobbits Hole type site found to consist of?
Ipswichian Fauna and Flora
What is a problem with the Bobbits Hole type site?
partially incomplete record following erosion in the latter stages
How was the Trafalgar Square type site analysed and what did it contain?
River Terrace deposits - archaeology consisted of hippo and hyena fossils
How were the glacial and interglacial stages and characteristics of the Ipswichian determined?
Using pollen grains from different flora to determine when it was cold or warm (glacial or interglacial)
What were 4 flora that were identified from their pollen in the record which indicated an interglacial period?
Tilia, Ulmus, Acer, Carpinus, Corylus and Quercus
What were 3 flora that were identified from their pollen in the record which indicated a glacial period?
Pinus, Betula, non-arboreal pollen
As well as the pollen grains found within the record for the Ipswichian, what were also found and how are they used?
Indicator species - provided evidence of warmer continental climate because they are the conditions they are found in today
What did Najas minor species indicate?
They are only found today in central and southern Europe. So if they are found elsewhere the climate there used to be like that of where they are found today
What did Trapa Natans species indicate?
They are only found today in China and Korea mostly today. So if they are found elsewhere the climate there used to be like that of where they are found today
What did Acer Monspesslanum species indicate?
They are mostly only found in Mediterranean climates of Europe. So if they are found elsewhere the climate there used to be like that of where they are found today
What were some fauna that were found in the British Archaeological record?
Hippopotamus, Lion, Brown Bear, Bison, and other extinct species like Giant Irish Elk, Straight tusked elephant and Auroch
What project was conducted which found many of the fauna remains in Britain?
AHOB
What is the water vole clock?
Water vole teeth adapt subtly over time to changes in environment and preserve very well in the record. They can be dated to determine climate at certain times
How much evidence do we currently have for the presence of hominids within the Ipswichian and why is this odd?
Non -strange because we have evidence for their existence before in Europe and more recently. It is therefore a gap in the hominid record
What are 3 ways we collect evidence of hominids?
Fossils, Archaeological industries (stone tools) and evidence of butchery
What are the similarities and differences in insolation between the Ipswichian and Holocene?
There were similar periods of warming then thermal max. then cooling. There were also similarities in the strengthening then weakening of the summer monsoon. But, there was not Younger Dryas equivalent in the Ipswichian
What are the similarities and differences in sea ice between the Ipswichian and Holocene?
Major difference was that Arctic winter sea ice may not have extended as far south as today. Another difference may have been that the Bering Strait was ice free during MIS 5e
How much further north was the arctic/northern hemisphere sea ice boundary?
800km
What did evidence of how the Arctic responded to the Ipswichian period come from?
Rock oyster in Alaskan peninsula indicated ice-absent conditions and the presence of sea shells that normally prefer warmer conditions
What were the differences in Arctic Flora between the Ipswichian and Holocene?
Trees in Northern Alaska were growing ~80km north of today’s position and in NE Siberia Larch was growing 600km north of today’s position
What evidence was there for the changes in Arctic Flora in Alaska?
Spruce pollen, cones and leaves indicated a warmer climate
What did the combination of evidence for Arctic flora in Alaska and Siberia suggest about Arctic temperatures during the Ipswichian?
4-8 degrees Celsius above today’s levels
How does a reduced sea ice extent impact our ability to determine past climate?
less sea ice means that there was less land area back then to collect the information
How can modelling sea ice help us to determine where we will find evidence of the past climate?
We can model sea ice from the past to determine areas where the record from an ice core will stretch back to so that we can choose where to go an collect an ice core to tell us about the past
How did sea level differ during the Ipswichian compared to today/Holocene?
Sea level was about ~8m above today
Why do we study the tropics and both hemispheres for past climate?
To understand the global changes
How do foraminifera composition reflect temperature changes?
If they are found with a higher magnesium or calcium content, this means the temperature was warmer
What did the foraminifera shells dated back to the last interglacial tell us about temperature?
It was about 1-2 degrees Celsius warmer
What would the coral reef have done during the Ipswichian and what does this suggest?
Extended 500km beyond current range meaning that the oceans and probably climate was warmer
What did Turney and Jones (2010) do and what did the find?
Collected temperature records for different parts of the planet and put it together to state that during the Ipswichian, the climate was 1.5 degrees Celsius warmer
What does the study carried out by Turner and Jones (2010) mean?
The ipswichian can therefore possibly be used as analogue for the 2 degrees Celsius threshold outlined by the IPCC as a dangerous level to determine the possible impacts of climate chaange
What is the closest model put forward by the IPCC which most closely simulates the Ipswichian period? What temperature rise does it predict?
Low Emmisions model - 1.8 degrees Celsius rise
What does the business as usual model from the IPCC estimate for a temperature rise?
6 degrees Celsius
Is the Ipswichian a good analogue for the Holocene and why?
No - because it was significantly warmer, wetter, higher in sea level, smaller in ice sheet coverage and lower in atmospheric CO2
Why was the Ipswichian so different to the Holocene?
There was a greater axial tilt on the obliquity cycle and the perihelion occurred in NH summer rather than winter
What might be a better analogue for the Holocene?
MIS 11
When was MIS 11?
400 kya
Why is MIS 11 a better analogue?
Similar astronomical characteristics (eccentricity is much less than MIS 5e). Meaning there were fewer cold stages and a prolonged warm period.
What are significant limitations of MIS 11? What might is serve better as?
There were no anthropogenic influences - it serves better as a ‘what should have happened’ scenario. There is also much less evidence for this MIS because the succeeding events eroded the record
What megafauna were found in the MIS 11 record?
Cave Bear, Giant Beaver, Rhinoceros. We also found evidence for Homo Erectus and Homo Heiderlbergenesis
