Citation

Geoscience Australia provides most of its products for free under a Creative Commons Attribution 4.0 International Licence. We only require that you reference the use of our data or information using the following citation:
Durney, D.W. & Kisch, H.J., 1994. A field classification and intensity scale for first-generation cleavages. AGSO Journal of Australian Geology and Geophysics  15:3:257-295. Australian Geological Survey Organisation, Canberra.

Abstract

The chief morphological characteristics and lithological associations of naturally occurring cleavage fabrics are reviewed with the aim of differentiating qualities that represent fabric type from those that represent fabric intensity, and incidental partings from the cleavage fabric itself. This leads to field-based descriptive classifications for types and intensity of rock cleavage which unify diverse previous observations and allow a more formal approach to the description of cleavage. Particular attention is given to first-generation cleavage and incipient cleavage in clastic rocks of low to very low metamorphic grade, although all cleavage types are considered. Two main divisions of cleavage type are recognised: (a) penetrative and (b) non-penetrative, according to the spacing of cleavage domains (where present) with respect to the width of dominant clastic (or detrital) grains. Each division includes three types, each of which is closely related to the lithology and texture of the parent rock (type 1, clay and slaty penetrative types; spaced, crenulation and scaly non-penetrative types). Each of the six cleavage types may display one (or less commonly both) of two kinds of intensity modulation at the mesoscale: shear zones and stripes. Fissility, defined as the small-scale crack-structure which develops along planes of bedding- and cleavage-fabric anisotropy in weathered mudrocks, is proposed as an index property reflecting the relative intensity of cleavage, bedding and intersection fabrics in these lithologies. Fissility-ratios can be quantified in the field by measurements of dimensional ratios of fissility-fragments. The ratios are given named class intervals and are quantitatively discussed with the aid of a logarithmic 3-axis diagram. A reference field-example illustrates a full progression of relative cleavage-fissility intensity from none, through incipient, to strong, in relation to a natural strain gradient. The influences of rock type, initial bedding anisotropy, strain and style of tectonic deformation on fissility-ratios are also discussed. Fissility-ratios provide a rapid means of evaluating the effects of regional variations of total fabric and deformation intensity in a given rock type in low- to very low-grade metamorphic environments; they also represent a new tool that may assist in the study of weak deformations, incipient cleavage, sensitivity of different rock types to cleavage development, deformational or tectonic regimes (as reflected by fissility-fragment shape fields) and fabrics in undeformed mudrocks.
Google map showing geographic bounding box with values North bound East bound West bound South bound
Downloads
For information on acquiring this product,
please contact Geoscience Australia Client Services via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Product Type/Sub Type

nonGeographicDataset - GA Publication - Journal

Constraints

license
Creative Commons Attribution 4.0 International Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

1994

Product Type

nonGeographicDataset

Topic Category

geoscientificInformation

Keywords

GA Publication
Journal
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Lineage

Unknown

Digital Transfer Options

onLine

DISTRIBUTION Format

pdf

Distributor

Role
distributor
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address

Metadata File Identifier

fae9173a-7152-71e4-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

2015-05-19

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

Role
pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Downloads
For information on acquiring this product,
please contact Geoscience Australia Client Services via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).