History of the Late Cenozoic Flashcards
What was the main orogenic process in the Late Cenozoic?
Mountain building of the Himalayas and Alps
What can be used to work out the past effect of sea ice volume effect?
Magnesium calcium ratio
More temp more Mg thus affected sea oxygen isotopes
What would the effect of all of the greenland land ice melting?
Sea level would be hundreds of meters higher diluting salinity losing the gulf stream
What stability problem is experienced by Antarctica?
The east side is very stable being wholly on land but the western side is surrounded by water and more dynamic
What would the effect of the whole of the western Antarctic ice sheet melting?
York and cambridge would become coastal town
What is the history of the west Antarctic ice sheet?
It has been prone to collapse in warm periods (sensitive to CO2 climate warming)
What produced CO2 in the Eocene?
India - Asia collision with resulting metamorphism and volcanics
What happens to the carbon cycle when the Tibetan plateau formed?
Increased weathering (Frost shatter), reducing the atmospheric C reservoir
What does global mean rate of chemical weathering depend upon?
Availability of fresh rocks and mineral surfaces brought about by fast tectonic uplift
What did increased weathering brought about by the Tibetan plateau ~55Ma do to earths climate?
cools global climate and starts transition to icehouse earth
What is evidence of the start of glaciers in the alps and the Mediterranean?
Massive increase of sediment flux
What is the Uk stratigraphy controlled by?
Tectonic subsidence and uplift
Global sea level changes
What was the transition of the Uk stratigraphy?
From sedimentary basins to regional uplift and compression
What caused compression and uplift in the UK?
Upward movement and collision of the alps and Mid-Atlantic ridge spreading
What was early Palaeogene deposition in the uk dominated by?
Shallow marine basins of the south of England especially the London and Hampshire basins
What was occurring in the Midlands in the early Palaeogene uk?
It was being eroded by the North Atlantic igneous province
What is the determining factor of deposition of the London basin?
By temperature and its relationship with sea levels
Where is one of the best examples of the Hampshire basin?
Alum Bay on the isle of wight - with the Bracklesham formation
What is the orientation of the Alum bay Bracklesham formation?
Near vertical hinting at tectonic rotation/ tipping
What dies the reading formation consist of?
Consists of clays and marls mottled with reddish iron oxide stain - palaeosols
What was the Reading formation originally?
grey soils deposited on a flood plain
What type of folding is present in Alum bay?
Monocline
What occurs towards the base of the Reading formation in Alum bay?
Thin conglomerate as a result of an unconformity
What type of landscape can be seen on the top of the chalk in Alum bay?
It has been eroded unevenly due to presence of limestone creating castic landscape
What is the London clay made up of?
Mix of unconsolidated mudstone with coarser sand and silt beds
How is the London clay controlled by transgressive-regressive cycles?
Clay deposition in deeper water during transgression
Deposition of sands and silts in shallower waters during regression
What was the environment like at the time of the London clay?
Sub-tropical seen by presence of turtle and alligator fossils ad palms in the midlands
What would sea temp have been around the time of the London clay?
Around 30* (Known due to research by Tom Dunkley in Ireland which showed se temp was 27)
What was the importance and complication of the London clays importance?
Was used for underground and cross rail but it is very unstable when exposed to water creating a concrete acid
What is the poole formation?
lower part of the Bracklesham Group, non-marine deltaic facie
What are the characteristics of the poole formation?
consists of sands, grey clays with plant debris & lignite beds and pipe clay (ball clay) beds
What is the barton clay?
Grey clay with white aragonitic shells
Related to very shallow marine shoreline deposits
What clasts can be seen in the Barton clay and what does it indicate?
Limestone casts which should be many units/ time below but must have been uplifted and eroded to be worked into the formation
What caused the end of the S.England Palaeogene depostion?
Evidence of regression in the Bouldnor and Bembridge formations
How old has the loch neigh depresseion been dated to?
By drilling sediments around the exterior is shows an age of 10 million years
