Hydro geology slides 11 to 20
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Transcript of Hydro geology slides 11 to 20
![Page 1: Hydro geology slides 11 to 20](https://reader033.fdocuments.net/reader033/viewer/2022042716/55c2b081bb61ebf22b8b47da/html5/thumbnails/1.jpg)
Hydrogeology WorkshopGeological History (3)
Permian and early Triassic times
• (~290 – 230 Ma);
• Surrounded by high ground;
• Arid/desert climate @ 15 - 20 degrees north of the equator;
• Land of braided rivers and flash floods.
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•~15 – 20 degrees north of the equator, arid/desert
climate;
•Eroding higher ground to the south and west;
•Subsiding basin north-south oriented basin;
•Huge amounts of material washed down, often as
flash floods;
•Braided rivers system, flowing from south to north,
meanders across the basin floor;
•Pretty inhospitable to life, even ignoring that 95% of
species had just gone extinct.
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Hydrogeology WorkshopGeological History (4)
Keep your eye on the
blue line.
• Hills eroding;
• Extension faults cause the
basin to subside;
• Sediments fill subsiding
basin.
All of this and this
ends up in here
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Upper Mottled Sandstone
(a.k.a. Wilmslow Sandstone)
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Transition Beds (between Upper Mottled
Sandstone and Helsby Sandstone)
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Helsby Sandstone
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Hydrogeology WorkshopGeological History (5)
Middle Triassic (~230 - 220 Ma)
•Lower relief and low-lying basin
receives mainly fine grained material
(silt and mud);
•Lakes form and evaporate, leaving
gypsum & anhydrite deposits.
•Periodic marine incursions.
Isolated areas of saline water
evaporate to leave extensive
deposits of rock-salt.
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•Lower topographic relief, sluggish river system only capable of
transporting fine-grained material silt/mud;
•Lakes form and evaporate;
•Periodic incursion of seawater, followed by evaporations;
•Mudstones and siltstones with evaporites, including significant rock-
salt deposits.
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Hydrogeology WorkshopGeological History (6)
Resulting Stratigraphy (handout)
Date (Ma) Period Epoch
Geology Map Formation No.
Old' clasisification New classification
DescriptionGroup Formation Group Formation
~230
Tria
ssic
f6d
Keuper
Keuper Saliferous Beds
Merc
ia M
udsto
ne G
roup
Wlkesley Halite Mainly rock-salt with this red mudstones
f6c
Middle Keuper Marl Middle Mudstone Mostly red-brown silty mudstone with anhydrite nodules. Silstones in lower part.
f6b
Lower Keuper Sailiferous Beds Northwich Halite Thick beds of red-brown rock-salt, separated by this mudstone horizons.
f6a
Lower Keuper Marl Lower Mudstone Alternating beds of musdstones and siltstones. Gypsum present and thin beds of rock-salt toward top.
f5
Keuper Waterstones Tarporley Siltstones Alternating beds dark red and greean shale (mudstone) and pink-red sanstones (fine grained). Silty toward the top.
~240
f4
Keuper Sandsdtones w/ Keuper Sandstone/Conglomerate.
Sherw
ood S
andsto
ne G
roup
Helsby Sandstone Mainly coarse grained, red-brown, grey/buff sandstones with pebbly bands and comnglomerates.
f3
Bunte
r
Upper Mottled Sandstone Wilmslow Sandstone Fine to medium grained soft red-brown sandstones mottled buff and grey. Some mudstones. Few pebbles.
~245
f2
Pebble Beds Chester Pebble Beds Medium and coarse grained red-brown sandstones. Scattered pebbles and some thin conglomerates.
~250
Permian
ef1
Lower Mottled Sandstone Kinnerton Sandstone Fine to medium grained soft red-brown sandstones. Some thin mudstones near top.
~290+ Carboniferous
d6b
Erbistock Beds Upper Coal Measures
Alternating mudstones and seatearths with a few thin sandstones.
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Hydrogeology WorkshopGeological History (7)
Then came the Ice Ages.......