EART3353: Geological Mapping

EART3353: Geological Mapping

Practical Exercise part 1 - Remote Sensing interpretation assessed exercise

This week you will begin part 1 of the assessed remote sensing interpretation exercise worth 15% of your grade for this unit. The objective of this exercise is to demonstrate an ability to characterise the surface geology and regolith cover with remote sensing data.

Several remote sensing images are supplied in the GIS package, from which you will undertake this interpretation for the provided map area. Any other data from the public domain may be accessed and used with appropriate citation. This includes published GSWA maps at similar scale however these should not simply be replicated you must do your own mapping from the data GSWA may not be correct!

Air/Satellite photos World Imagery at low and high resolution (needs internet)

Landsat 8 composite image. Red = Band 7; Green= Band 5; Blue = Band 8.

The sun is shining from the northeast for this image

ASTER images: Regolith Ratios, Ferric Oxide Content, Opaque Index

ASTER Photogrammetric Digital Elevation Model

Radiometrics Total Count & Ternary images

Before beginning this exercise please ensure you have done the following:

1 completed the introductory GIS tutorial including watching the video content as needed

2 watched the following online lecture content:

Before Week 2 Remote Sensing Concepts

Before Week 3 Remote Sensing Applications

Task 1 Regolith Mapping (10 Marks)

Your first task is to characterise the regolith surficial sediment cover (or lack thereof), with the aim of defining regions of outcrop to interpret further.

To begin this interpretation, please undertake the following steps.

Construct the GIS project. At a minimum, you will need new GIS layers for the following:

Roads and tracks (you may extend the existing files) as polylines

Cultural features (e.g. mine sites and town sites, power lines etc etc) as polygons & polylines

Waterways (you may extend the existing files) as polylines

Regolith interpretations as polygons

Now, map the cultural features these will be excluded from the later mapping and to identify possible effects on other datasets.

Include roads, tracks, rail, mine sites, town sites and other infrastructure such as pipes and power lines. Pre-defined data will be a good start point but you may need to add some local information and/or update for any recent changes.

The next step is to interpret the surface hydrological system. This step is necessary as you need to understand the erosion and deposition systems that make your regolith. In particular, look to identify five zones of the sediment transport system:

Drainage divides: these will generally relate to hill tops and or ridges and geological exposure is most likely.

Higher-energy: where there is steep topography and straight, narrow, v-shaped valleys, with more acute channel intersections (angle < 60 degrees), and no floodplain these indicate dominance of debris flows (colluvium), and likely geological exposure;

Lower-energy: where there is shallower topography and broad flat-bedded valleys, with anabranching or slightly meandering channels, less acute channel intersections (angle > 60 degrees) and a floodplain these indicate active fluvial transport and likely alluvial sediment cover;

Depositional margin: where there is shallow topography, with divergent channels and alluvial fans and likely alluvial sediment cover;Lacustrine zone: where there is a broad region with no channels, very flat topography and likely lacustrine sedimentary cover..

Figure: Example classification for a catchment divide zone in red, higher-energy zone in green, lower-energy zone in yellow, depositional zone in cyan. Channels indicated in blue.

Clay vs silt = al content, k content

From the remote sensing imagery, map the surface geology into the following classes. The domains should all be relatively large:

Exposed bedrock and colluvium (gravitationally transported debris)

In remote sensing there is often not opportunity to separate colluvium from bedrock but you may see a debris flow where topography is very steep

Alluvial deposits (from fluvial transport) from water

Alluvial deposits may be further subdivided (e.g. channel deposits, floodplain, terrace, alluvial fans)

Lacustrine deposits (low-energy deposits)

Lacustrine deposits may also be further subdivided (e.g. high/low clay content, evaporite)

Aeolian deposits (sand dunes, drifts etc)

In-situ regolith (chemically weathered bedrock)

Unclassified (e.g. due to cultural features)

Fill out the characteristics of these classes in the table below to help you explain what defines these...and then you can use this to map them out try to be consistent!

If you are struggling refer to the Clarke (1994) paper and/or GSWA mapping and compare to your data.

Class Landsat C758 Regolith Ratio (ASTER) Radiometrics Ternary

Exposed bedrock & colluvium Brown red, dark/reddish, rough, layered responding to iron rich rocks, indicating fresh rock, not weathered. Dark pink pink, purple, yellow, green, elongate, rough

Varying degrees of red (brightness), SWIR, pinkness coming from vegetation more = darker, less = lighter. Dark, black, yellow-orange (increase in K + Th = felsic) near lake, dark green brown, elongate, smooth, sharp boundaries geological contact.

Mafic/ultramafic rocks due to low emitting gamma rays

Alluvial Deposits Beige, white (sands), light green (vegetation), fern pattern, thin channels. Yellow, brown, beige and green

High in red and green and low in blue Cyan, blue/green

Depleted levels of K in sediments/sedimentary

Lacustrine deposits Cyan, light blue Aeolian deposits In-situ regolith

Task 2 Exposed bedrock geology map (5 marks)

In this part of the interpretation you will understand and assign geology interpretations to the exposed bedrock and colluvium dominated area (class a from task 1), please undertake the following steps.

Using your surface interpretation, identify the areas where remote sensing & radiometric imagery may be expected to reflect the bedrock geology:

Exclude all transported cover, waterbodies and unclassified areas

Include the exposed bedrock and colluvium area these should be quite large

With extreme care, in-situ-regolith areas can be interpreted

Make a new polygon shapefile to hold your bedrock geology. This needs to have fields suitable for classifying geology into lithostratigraphic units, using the regional stratigraphy as in the below table.

Using the 1:500,000 geology map, define the character of each major lithostratigraphic unit in each remote sensing data set.

Using your table, map the exposed regions into lithostratigraphic units. Look out for possible new units that may not be in your classification and also sub-units within existing units

It is advised to begin either at the base of the stratigraphy and work upwards, unless there is a clear marker horizon higher up that you can use.

The bedrock geology and regolith interpretations may all be submitted on the same map or alternatively as two separate maps. If separate maps are submitted, you must ensure the characteristics of the map layout are identical.

Lithostratigraphic unit Landsat C758 Regolith Ratio Radiometrics Ternary

Lunnon Basalt Kambalda Komatiite Devon Consols Basalt Kapai Slate Paringa Basalt Black Flag Group Other Units Submission and Assessment:

Your interpretations should be submitted via LMS as A3-scaled map(s). PDF format is preferred over image formats. Normal late penalties and special consideration rules apply. Assessment criteria are pasted below