WJEC A2 Geology
BGS Mapwork
Recognising Geological Structures
I.G.Kenyon
Moreton-in-Marsh
Horizontal beds
1:50,000 Sheet 217
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
Moreton-in-Marsh
1:50,000 Sheet 217
Graben
Ticks on faults indicate
downthrown side
Horst
Graben
Moreton-in-Marsh
1:50,000 Sheet 217
Outliers-areas of younger rock
completely surrounded by older rock
Cheddar 1:25,000 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
Cheddar 1:25,000 Sheet ST 45
N
North side dips more
steeply (dips 42-60°)
Outcrops narrower
Oldest bed
in the core
of the fold
Repeated outcrop
pattern, only core bed
is not repeated
Slight plunge to the east as core
bed gets narrower in outcrop
Asymmetrical Anticline
South side dips more gently
(dips 25-30°) Outcrops wider
Cheddar 1:25,000 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
Monmouth 1:50,000 Sheet 233
Beds above and below unconformity
have parallel outcrop patterns and
the same dip and strike values
C3 quartz conglomerate forms a
parallel unconformity between the
upper and lower old red sandstone
Angular overstep
unconformity here
between the carboniferous
limestone and the upper
coal measures
Craven Arms 1:25,000 Sheet SO48 Solid & Drift
Account for the V shaped pattern
of outcrop of bed b7b here
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
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
Haverfordwest 1:50,000 Sheet 228
Describe the main
fold structure here,
refer to strike and
dip values, symmetry
and plunge
Chepstow 1:50,000 Sheet 250
Describe the main fold structure
here, refer to strike and dip
values, symmetry and plunge
Approximate
position of fold axis
Chepstow 1:50,000 Sheet 250
This fault dips east at 79°,
identify the fault type
Identify this deposit and
account for its distribution
on this map extract
Haverfordwest 1:50,000 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
Haverfordwest 1:50,000 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
Hawes 1:50,000 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
Chepstow 1:50,000 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
Cockermouth 1:50,000 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
Ayr 1:50,000 Sheet 14(W)
If this fault dips steeply to the
SSW, what is the type of fault?
Ayr 1:50,000 Sheet 14(W)
Describe the main fault trends on the extract above. Identify
2 Grabens, 2 Horst Wedges and an area of Step Faulting
Carmarthen 1:50,000 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
Carmarthen 1:50,000 Sheet 229 Solid
F1
F2
Name the types of faults F1 and F2 on the cross section above
Alloa 1:50,000 Sheet 13 Solid
Account for the repeated outcrop of bed dc2 on the map extract above
Alloa 1:50,000 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.
Alloa 1:50,000 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
Brough-under-Stainmore 1:50,000 Sheet 31 Solid
Describe the outcrop of the quartz dolerite qD and
outline the likely nature of this igneous intrusion
Chapel en le Frith 1:50,000 Sheet 99 Solid
Identify 2 major fold structures on the map extract above
Refer to dip and strike, symmetry and plunge where appropriate
Chapel en le Frith 1:50,000 Sheet 99 Solid
Describe the relationship between geological
structure and topography on the cross section above.
Comment on the areas highlighted by the boxes.
Winchester 1:50,000 Solid & Drift
a
b
Cross section
shown on next slide
Identify the major fold structure on the map extract above
Winchester 1:50,000 Solid & Drift
a
b
Describe and explain the relationship between
topography and structure on the cross section above
Falmouth 1:50,000 Sheet 352 Solid & Drift
Grampound Grit
Inliers-outcrops of older rock completely
surrounded by younger rocks
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
The End
Ash deposits of the Las Canadas
Volcano, Tenerife, Canary Islands