Field project tutorials 2002 - Day 4

Day 4: Notebook entries

Date		Location
Weather	Sunny & warm, but breezy; few clouds; cooler at higher levels.
Hazards	Steep grassy slopes (slippery in wet) and precipitous cliffs; several stream/river sections with fast-flowing water and waterfalls/rapids. Thirst; sunburn; sunbathing snakes (slow moving after hibernation).
First-aid	Dr. Geoff Lloyd
Mood
Aims	To traverse through the quartzite forming the lower thrust sheet collecting samples for thin-section preparation and subsequent strain analysis. When collecting samples in the field for laboratory analysis it is essential that they should be geographically oriented: select an obvious planar surface (this does not have to be geologically significant) and measure its strike and dip. This reference orientation can then be used to position the samples as they were in the field when you have returned to the laboratory. It is then possible to cut specimens parallel to geologically significant planes, based on geological measurements you made in the field at the sampling site.

Field Notes

Walk from GR 112 054 to 084 052 (i.e. from the top of the thrust sheet towards the thrust plane), taking oriented samples at the following locations:

110 054
092 053
087 052
084 052.

The samples were subsequently cut parallel in to mutually perpendicular specimens back in the laboratory and analysed under the optical microscope. The following observations were made, from which it is possible to derive the progressive strain history (choosing the appropriate methodology yourself) in the quartzite via use of a Flinn Plot and the following strain analysis summary template:

LOC	XY PLANE			XZ PLANE					YZ PLANE
	X/Y	Xorient	Yorient	X/Z	Xregional	Xlocal	Zorient	g	Y/Z	Yorient	Zorient
1
2
3
4

Location 70. GR 110 054.

An identical granoblastic texture with euhedral and equant quartz grains is observed on each of 3 section planes, oriented: 014/64E, 110/90, 014/25W, respectively. This microstructure is shown in Fig. 28.

Location 71. GR 092 053.

The section plane cut parallel to 110/90 (Fig. 29) shows subhedral quartz grains elongate at a high angle to the weak foliation plane (014/64E) observed in the field, which intersects the section plate as a 'stretching' lineation plunging 64/104.

The section plane cut parallel to 014/64E has granoblastic euhedral quartz grains and a very weak stretching lineation oriented 64/104 (Fig. 30).

The section plane cut parallel to 014/25W has granoblastic euhedral quartz grains and a weak horizontal stretching lineation oriented 00/194 (Fig. 31).

Location 72. GR 087 052.

The section plane cut parallel to 110/90 (Fig. 32) shows subhedral quartz grains elongate at a high angle to the foliation plane (014/64E) observed in the field, which intersects the section plate as a 'stretching' lineation plunging 64/104.

The section plane cut parallel to 014/64E has euhedral quartz grains and a stretching lineation oriented 64/104 (Fig. 33).

The section plane cut parallel to 014/25W has euhedral quartz grains and a horizontal stretching lineation oriented 00/194 (Fig. 34).

Location 73. GR 084 052.

The section plane cut parallel to 110/90 (Fig. 35) shows anhedral quartz grains elongate oblique to the foliation plane (014/64E) observed in the field, which intersects the section plate as a 'stretching' lineation plunging 64/104.

The section plane cut parallel to 014/64E has euhedral quartz grains and a strong stretching lineation oriented 64/104 (Fig. 36).

The section plane cut parallel to 014/25W has euhedral quartz grains and a strong horizontal stretching lineation oriented 00/194 (Fig. 37).

Daily Summary

(remember to summarise your observations & to begin to evolve ideas about this region).

Introduction	Day 1	Day 2
Day 3	Day 4	Day 5