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Some comments

Vertical exaggeration On all the profiles you’ve drawn the vertical and horizontal scales are not the same Whelan Cove – Canning: vertical scale is 1:5000, horizontal scale is 1: This is ten times vertical exaggeration

This: …should be this.

This… …should be this.

And this… …should be this.

Much easier to compare the shape of these two than…

… these two, even though here their vertical scales are identical.

Calculating vertical exaggeration Vertical exaggeration (VE) is the vertical scale divided by the horizontal scale Remember that scales are ratios to begin with If vertical scale is 1:5000 and horizontal scale is 1:50000 the VE is = (1/5000)/(1/50000) = 50000/5000 = 10 If vertical scale is 1:20000 and horizontal scale is 1:50000 the VE is = (1/20000)/(1/50000) = 50000/20000 = 2.5

Structure and Geological Maps

Rule of Vs (vees) Helps in reading geological maps As a contact changes elevation, when viewed from overhead (map view), it shifts in the direction of dip i.e., a contact “vees” in the direction of dip

Rule of Vs a)Shallowly dipping contacts make “large” Vs b)Horizontal contacts run parallel to the topographic contours c)Steeply dipping contacts make “small” Vs d)Vertical contacts run straight across topographic contours

Shallowly dipping contacts

Horizontal contacts

Steeply dipping contacts

Vertical contacts

Horizontal (parallel to contours) Shallow dip (big “vees”) Steep dip (small “vees”) Vertical dip (runs straight across topo)

Question 1 what is the value of the contours?

Question 1 position the contours

Question 1 draw the surface

Question 1 where do the contacts cut the surface?

Question 1 what is the orientation of the contacts? Hotizontal!!! (contacts follow contours)

Question 1 fill the units

Question 1 finished! At least part (a)

Question 2a 3 is younger than 2 is younger than 1

Question 2a therefore contact between 3 and 2 slopes towards 3 (i.e., 3 is on top of 2)

Question 2a likewise contact between 2 and 1 slopes toward 2 (i.e., 2 is above 1)

Question 2a contacts between 3 and 2 join; separate 3 from 2 everywhere

Question 2a separate 2 from 1

Question 2a colour/shade

Question 2a label

Question 2b let’s just focus on the boundary between layers 2 and 3

Question 2b rule of vees tells us that the 2/3 boundary on the west side dips…

Question 2b …to the east

Question 2b rule of vees tells us that the 2/3 boundary on the east side dips…

Question 2b …vertically

Question 2b complete the line…and draw the others in the same way!

A couple of points… Rock units are assumed to be planar and of equal thickness throughout the area Wider outcrop in one place and narrower outcrop in another indicates differences in dip When drawing sections try to maintain thickness of units around folds.

Contacts are parallel and units maintain thickness

Structure labs/drawing Recent labs often “sloppy” Take time to draw contacts properly –Units must maintain thickness –Contacts should be parallel and “smooth” –Contacts should be in the right place –Angles should be approximately correct (use a protractor if you cannot draw angles to within 10°) and consistent

Block diagrams… See if you can work these ones out for yourself But ask questions Hint: look at the strike and dip symbols.

Dykes and faults This exercise is fairly intuitive Note: we cannot tell the absolute sense of motion on a fault thus we indicate relative motion with two “half” arrows

Strike and dip Put strike FIRST (up to 3 digits) Then DIP (only 2 digits) Then DIP direction 110 / 25 NE

Drawing a strike and dip symbol (important for final test) What is the orientation determined? 115/37 NE

Drawing a strike and dip symbol 115/37 NE What is the strike? 115 What is the dip direction? NE What is the dip? 37 Done! Remember that if it is a cleavage measurement, the symbol is like this… N

Geological Maps

Wolfville map Information is available on the: MAP …on the LEGEND …and on the CROSS-SECTIONS Also some more detailed information in the “Descriptive Notes”

Wolfville Map questions 6 – (relatively straightforward) questions Some hints –Use the legend and cross-sections –“a deep well” means hundreds of metres (scale of the cross sections) –Contacts are: Conformable (bedding) Cross cutting (faults, intrusions, unconformities) –For question 12, think of the rule of vees –For question 13, think of your fieldtrip to Black River