WJEC A2 Geology

1
WJEC A2 Geology
BGS Mapwork
Recognising Geological Structures
I.G.Kenyon
2
Moreton-in-Marsh 150,000 Sheet 217
Horizontal beds Evidence symbols Bed outcrops
run parallel to contour lines Outcrop
pattern controlled by relief/topography

Youngest bed
Oldest bed LLi

No strike and dip values can be given
3
Moreton-in-Marsh 150,000 Sheet 217
Graben
Ticks on faults indicate downthrown side
Horst
Graben
4
Moreton-in-Marsh 150,000 Sheet 217
Outliers-areas of younger rock completely
surrounded by older rock
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Cheddar 125,000 Sheet ST 45
Inlier-an area of older rock completely
surrounded by younger rocks
Older Carboniferous Limestone
Younger Triassic red mudstone
Unusually this inlier also forms a hill
6
Cheddar 125,000 Sheet ST 45
N
Repeated outcrop pattern, only core bed is not
repeated
North side dips more steeply (dips 42-60)
Outcrops narrower
Anticlinal Axis
Oldest bed in the core of the fold
Slight plunge to the east as core bed gets
narrower in outcrop
Asymmetrical Anticline
South side dips more gently (dips 25-30)
Outcrops wider
7
Cheddar 125,000 Sheet ST 45
MMG overlaps DCg here
DCg shows angular overstep here as it extends
over several older rocks

Lower older series dip North 60-80 and
strike East-West

DCg is a basal conglomerate and is
unconformable on the older carboniferous rocks

Upper younger series are horizontal
8
Monmouth 150,000 Sheet 233
Beds above and below unconformity have parallel
outcrop patterns and the same dip and strike
values
Angular overstep unconformity here between the
carboniferous limestone and the upper coal
measures
C3 quartz conglomerate forms a parallel
unconformity between the upper and lower old red
sandstone
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Craven Arms 125,000 Sheet SO48 Solid Drift
Account for the V shaped pattern of outcrop of
bed b7b here
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Malmesbury One inch Sheet 251 Solid Drift
Describe the strike and dip of the Carboniferous
beds here
Identify the relationship between beds d5 and f6
here
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Malmesbury One inch Sheet 251, Solid Drift
Describe the main fold structure here, refer to
strike and dip values, symmetry and plunge
Name this feature
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Haverfordwest 150,000 Sheet 228
Describe the main fold structure here, refer to
strike and dip values, symmetry and plunge
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Chepstow 150,000 Sheet 250
Describe the main fold structure here, refer to
strike and dip values, symmetry and plunge
Approximate position of fold axis
14
Chepstow 150,000 Sheet 250
This fault dips east at 79, identify the fault
type
Identify this deposit and account for its
distribution on this map extract
15
Haverfordwest 150,000 Sheet 228
Identify this feature
Describe and identify the main fold structure in
the map extract above. Refer to dip and strike
values, symmetry and plunge where appropriate
16
Haverfordwest 150,000 Sheet 228
Identify the relationship between beds (b4 and
d4) and (d2 and d4) in this box
Describe and identify the main fold structure in
the map extract above. Refer to dip and strike
values, symmetry and plunge where appropriate
17
Hawes 150,000 Solid Drift
Describe the evidence on the map for the
Carboniferous beds GL and DBL being horizontal
Describe the fold structures in the InG beds
within this box
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Chepstow 150,000 Sheet 250
Describe the strike and dip of the Carboniferous
beds BRL, BRD, GuO and CDLin this box
Identify an angular unconformity on the map
extract and locate examples of overstep and
overlap
19
Cockermouth 150,000 Sheet 23
If the Crummock and Waverbank Faults dip North
East, what type of faults are they?
Identify an area of Step-Faulting and a Horst
Block on the map extract
20
Ayr 150,000 Sheet 14(W)
If this fault dips steeply to the SSW, what is
the type of fault?
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Ayr 150,000 Sheet 14(W)
Describe the main fault trends on the extract
above. Identify 2 Grabens, 2 Horst Wedges and an
area of Step Faulting
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Carmarthen 150,000 Sheet 229 Solid
This fault plane dips steeply to the South East.
Identify the type of fault
This fault plane dips steeply to the South East.
Identify the type of fault
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Carmarthen 150,000 Sheet 229 Solid
F1
F2
Name the types of faults F1 and F2 on the cross
section above
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Alloa 150,000 Sheet 13 Solid
Account for the repeated outcrop of bed dc2 on
the map extract above
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Alloa 150,000 Sheet 13 Solid
Describe and identify the major fold structure on
the map extract above. Refer to dips and strikes,
symmetry and plunge where appropriate.
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Alloa 150,000 Sheet 13 Solid
Metamorphic Aureole
The Ochil Fault dips at a high angle to the
South. Which is the downthrown side? What type
of fault is the Ochil Fault? Account for the
variation in width of the metamorphic aureole
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Brough-under-Stainmore 150,000 Sheet 31 Solid
Describe the outcrop of the quartz dolerite qD
and outline the likely nature of this
igneous intrusion
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Chapel en le Frith 150,000 Sheet 99 Solid
Identify 2 major fold structures on the map
extract above Refer to dip and
strike, symmetry and plunge where appropriate
29
Chapel en le Frith 150,000 Sheet 99 Solid
Describe the relationship between geological
structure and topography on the cross
section above. Comment on the areas highlighted
by the boxes.
30
Winchester 150,000 Solid Drift
a
b
Cross section shown on next slide
Identify the major fold structure on the map
extract above
31
Winchester 150,000 Solid Drift
a
b
Describe and explain the relationship between
topography and structure on the cross section
above
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Falmouth 150,000 Sheet 352 Solid Drift
Inliers-outcrops of older rock completely
surrounded by younger rocks
Grampound Grit
River Allen
Mica-rich dykes (Minette)
Truro School
River Kenwyn
Falmouth Series
Portscatho Series
Quartz Porphyry Dykes
Mylor Series
Sediments are Devonian 408-360 Ma
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The End
Ash deposits of the Las Canadas Volcano,
Tenerife, Canary Islands