Abstract

Re-examination of the Ordovician geology between Mandurama and Bigga in the Lachlan Orogen of central western New South Wales has produced new interpretations of the stratigraphy and structural geology. The Abercrombie beds have been previously inferred to comprise an Ordovician turbidite package with interbedded black shale bands. Although hampered by a paucity of fossil ages, new data suggest that the Ordovician geology of this region instead represents an imbricate stack of Lower Ordovician turbidites (Adaminaby Group) and Upper Ordovician black shales (Warbisco Shale). Structural data from the north of this region suggest that duplication occurred in a D1 event (with formation of broadly east-west to west-northwest-trending thrust slices or fold limbs) and was accompanied by formation of cleavage and isoclinal folds. Thrusting of the Adaminaby Group and Warbisco Shale over or under the Lower Ordovician Coombing Formation (southern part of the Molong volcanic belt) also occurred at this time. East-vergent imbrication and thrusting and formation of a regional near-meridional steeply west-dipping cleavage occurred in the D2 event, when D1 thrusts or folds were folded around overturned (east-vergent) D2 folds. These new data also suggest that there is a north-to-south gradient in the intensity of the D2 deformation, with D2 effects decreasing from south to north approaching the Lachlan Transverse Zone. Such a gradient mirrors similar but more subtle local changes from the north. Together, they imply that the Lachlan Transverse Zone was a major zone of weakness during north-south shortening that resulted in the formation of D1 structures but was relatively rigid in local areas during the regional D2 deformation that resulted from east-west shortening when it formed a major tear/accommodation zone. This D2 rigidity may be caused by strength imparted by the earlier emplacement of large (variably mineralised) intrusive/volcanic complexes along the transverse zone.
Google map showing geographic bounding box with values North bound -30.25 East bound 153.15 West bound 141.0 South bound -39.25
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Product Type/Sub Type

dataset - External Publication - Scientific Journal Paper

Constraints

license
Creative Commons Attribution 3.0 Australia Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

2007

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

External Publication
Scientific Journal Paper
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-30.25
East bound
153.15
West bound
141.0
South bound
-39.25

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Unknown

Digital Transfer Options

onLine

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

Metadata File Identifier

a05f7892-fa2f-7506-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

2010-10-21

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

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pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Related Links
For information on acquiring this product,
please contact the Geoscience Australia Sales Centre via:

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

Please note that support hours are 9 am to 5 pm weekdays