Table 17. (cont.)

/SAMPLE RELATIVE STANDARD AXES EIGENVALUES ERROR IN COMMENTS ON THE DESTRAINING
/NUMBER AXES DEVIATION ATTITUDES CO-ORDINATE
SIZES OF AXES 1 INTERCEPTS SECTION CLASTS USED DISTRIBUTION AXIAL RATIO
I$ 7 1 227/05 1981 22 -- 2-36 | all random 140
1.68 | 109/50 63 22. O92. 226 I] all random Puste,
2.50 19 320/38 622 60 X- .009 III all random 1.65
$ 8 1 252/22 S73 98 Z- .237 | all random 1.38
1.46 st2 096/70 478 6. T¥4. 17 II all deltoid 1.62
1.54 12 348/06 101 G . Sk .237 III all random 1.00
8 1 252/22 799 281 Z- .084 | all random 1.38
1.41 04 088/70 1270 5 2 2¥n..042 II all random 1.46
1.44 04 348/05 297 5  X- .844 HII all random 1.00
wea 4 197/02 19 a; A 1p | all random 1.50
v4 .06 106/30 12 2 S75. 468 I] all random 4.35
1.47 .09 291/60 20 11 X= ..151 HI} all random 1.32
9 1 202/09 196 16 = Z- .044 | chert random 1H
1.10 01 108/24 78 16° 5¥= .034 Il chert random ¥.35
1.43 02 309/64 149 71 X- .030 Ill chert random 1.32
] 1 086/40 29 S ¢ée 059 | quartz random 1.00
1.09 01 192/19 74 6 f¥e. 05/7 I] quartz random 1.20
| 1.38 .02 305/44 41 20 - Ger Gar Ill quartz random 1.32
$10 1 051/26 58 26-080 | all random To
| 1.44 .03 186/56 35 ea ene . 182 II all random 1.38
| 1.91 05 306/21 60 20° = Xs. .061 III all random 1.46
| 10 1 050/29 64 33--72- 098 | chert random 4:45
4.43 04 173/45 34 Ion 2 8e. 062 ll chert random 4:25
y Me 06 300/32 66 ia: sens: 12S Ill chert random 1.58
| 10 1 057/33 138 5d = tee, 025 | quartz random 1.49
| 1.30 01 194/29 100 4B Se OP? Il quartz random 125
| 1.68 01 312/22 156 fo" “tae. G32 Ill quartz random 1.43
$11 1 202/22 18 5... S25, 096 | all random 1.00
1.05 04 294/05 66 be ANS. ST II all random 1.27
| 1.26 04 033/68 29 17. _X- .080 III all random £15
|Standard1 102/89 206 52 aes. Bas True axial ratio 1-1.5-2.5
1.541 03 267/02 54 39 Y- .097 True orientation vertical-270/00-180/00
2.518 - << OF 180/00 163 39 = X-_-.081
$ This determination is chosen as representative of the strain for that sample

ble to the test case. These are samples 5, 9 (trial 2), and 10
(trial 3). Within the suite of rocks examined these have moderate
to low strains.

The GOFIs give an estimate of the geometric fit of the deter-
mined ellipses to an ellipsoid but do not necessarily provide an
estimate of how good the ellipsoid approximates the strain
ellipsoid.

Deviations from geometric deformation

Deviations from the ideal case of geometric strain are in part
a result of irregular grain shape, viscosity contrasts and clast
composition.

Grain shape

The strain measurement technique requires that markers (clasts)
be treated as ellipsoids. The sections through the clasts are then

94

treated as ellipses. The clasts measured were never truly ellipti-
cal. They exhibit a good to very poor fit to ellipses. Many of
the clasts of all compositions are angular within the Guyet For-
mation conglomerate. Most angular are the chert and pelite
clasts. Volcanic fragments are the most rounded and they are
the best approximations to ellipses, but are not abundant. Most
abundant are sand size quartz grains which are subangular to
rounded. Larger quartz grains are generally more angular. Chert
grains which are very flat and elongate display a moderately
good fit to elliptic shapes. In general, the greater the deforma-
tion, the easier it is to fit an ellipse to the clasts.

An irregularly shaped clast will not follow the deformation
path of an ellipse. Deformation will be accommodated in irreg-
ular and unstable parts of the grain. This can be thought of
as attainment of a shape most amenable to straining. This con-
cept is discussed further in the section on ‘‘Clast composition
and mechanisms of deformation’’, in relation to the strain beha-
viour of quartz and chert. Interaction or noninteraction with
neighbouring clasts will partly govern how irregularities affect