Dyke-induced fault and pit crater measurements and predicted dyke properties offshore NW Australia (NERC Grant NNE/R014086/1)

There are two components to this dataset: (1) fault analyses used to estimate underlying dyke properties, imaged in 3D seismic reflection data; and (2) dimension measurements and calculations of pit craters associated with the dykes and faults. This dataset specifically supplements https://webapps.bgs.ac.uk/services/ngdc/accessions/index.html#item170389. The seismic reflection data are located offshore NW Australia and image a series of Late Jurassic dykes and overlying dyke-induced normal faults; these structures occur within a sedimentary basin and are now buried beneath several kilometres of rock. The specific seismic reflection dataset used for this study so far is the Chandon 3D survey, which is available through https://www.ga.gov.au/nopims and is also deposited within the NGDC. Dyke-induced faults: Analyses of these faults uses an array of point pairs, defined by X, Y, and Z co-ordinates, that mark where certain sedimentary beds are intersected by the fault in its footwall and hanging wall. Mapping of these points for 11-14 sedimentary horizons was conducted using Petrel seismic interpretation software. From the footwall and hanging wall point pairs, the throw, heave, displacement, and dip of each fault was calculated. By measuring distances between corresponding point pairs on opposing faults, graben width properties and estimated down-dip fault continuations were calculated. The expression of dyke-induced faults observed at the surface in active volcanic areas is often used to estimate dyke location, thickness (expected to roughly equal the heave on overlying faults), and upper tip depth (expected to occur where overlying, oppositely dipping faults meet; i.e. the point of the ‘V’). This study represents the first time natural dyke-induced faults and underlying dykes have been imaged in 3D and quantitatively studied. The dataset presented here allows hypotheses concerning relationships between dyke-induced fault geometries and dyke properties to finally be tested, and provides insight into normal fault kinematics; this will be useful to structural geologists and volcanologists. Pit craters: These features are enigmatic, quasi-circular depressions that commonly occur at the surface above inferred dykes and faults. The long axis and short axis lengths, as well as the area and depression depth, of the pit crater plan-view morphologies were measured. 3D seismic reflection data reveal the pit craters are underlain by pipes, for which the height, diameter, and volumes are calculated. These pipes often connect to dykes and faults, providing the first conclusive evidence that dyking and faulting mechanisms can drive pit crater formation. However, although studies of pit craters on other planets has used their surface shape to predict subsurface processes and geology, the data presented here suggest pit crater surface expressions are not diagnostic of formation mechanisms or geology.

Date (Revision): 2022-02-18

Citation identifier: http://data.bgs.ac.uk/id/dataHolding/13607910

Point of contact

Organisation name	Individual name	Electronic mail address	Role
University of Leeds	Craig Magee	not available	Originator
University of Leeds	Craig Magee	not available	Principal investigator
British Geological Survey	Enquiries	not available	Distributor
British Geological Survey	Enquiries	not available	Point of contact

Maintenance and update frequency: notApplicable

GEMET - INSPIRE themes, version 1.0

Geology

BGS Thesaurus of Geosciences

NGDC Deposited Data
Seismic reflection surveys
Citable Data
Dykes
Faults

dataCentre

Keywords

NERC_DDC

Access constraints: Other restrictions

Other constraints: licenceOGL

Other constraints: Available under the Open Government Licence subject to the following acknowledgement accompanying the reproduced NERC materials "Contains NERC materials ©NERC [year]"

Use constraints: Other restrictions

Other constraints: The copyright of materials derived from the British Geological Survey's work is vested in the Natural Environment Research Council [NERC]. No part of this work may be reproduced or transmitted in any form or by any means, or stored in a retrieval system of any nature, without the prior permission of the copyright holder, via the BGS Intellectual Property Rights Manager. Use by customers of information provided by the BGS, is at the customer's own risk. In view of the disparate sources of information at BGS's disposal, including such material donated to BGS, that BGS accepts in good faith as being accurate, the Natural Environment Research Council (NERC) gives no warranty, expressed or implied, as to the quality or accuracy of the information supplied, or to the information's suitability for any use. NERC/BGS accepts no liability whatever in respect of loss, damage, injury or other occurence however caused.

Other constraints: Available under the Open Government Licence subject to the following acknowledgement accompanying the reproduced NERC materials "Contains NERC materials ©NERC [year]"

Spatial representation type: Vector

Language: English

Topic category

Geoscientific information

Geographic identifier: EXMOUTH PLATEAU [id=924210]
British Geological Survey Gazetteer: Geographical hierarchy from Geosaurus 1979 creation

Begin date: 2021-02-01

End date: 2022-02-18

Unique resource identifier: WGS 84 (EPSG::4326)

Distribution format

Name	Version
Microsoft Excel	witheld
PDF	witheld
Comma-separated values (CSV)	witheld
Text file (TXT)	witheld

Distributor contact

Organisation name	Individual name	Electronic mail address	Role
British Geological Survey	Enquiries	not available	Distributor

OnLine resource

Protocol	Linkage	Name
WWW:DOWNLOAD-1.0-http--download	https://webapps.bgs.ac.uk/services/ngdc/accessions/index.html#item172132	Data

OnLine resource

Protocol	Linkage	Name
WWW:LINK-1.0-http--related	https://doi.org/10.5285/2edf6c47-fd18-4540-b449-b78d12422193	Citation Information - Digital Object Identifier (DOI)

Hierarchy level: Dataset

Other: dataset

Conformance result

Title: INSPIRE Implementing rules laying down technical arrangements for the interoperability and harmonisation of Geology

Date (Publication): 2011

Explanation: See the referenced specification

Pass: No

Conformance result

Title: Commission Regulation (EU) No 1089/2010 of 23 November 2010 implementing Directive 2007/2/EC of the European Parliament and of the Council as regards interoperability of spatial data sets and services

Date (Publication): 2010-12-08

Explanation: See http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2010:323:0011:0102:EN:PDF

Pass: No

Statement: To provide a framework for the fault analysis, 11-14 reflections corresponding to sedimentary beds were mapped across areas of dyke-induced faults; these horizons mapped are all offset by dyke-induced faults. The reflections picked were selected based on ease of interpretation across the desired area and to ensure a good spatial resolution to the data. Mapping was conducted in Petrel seismic interpretation software on inlines and crosslines spaced 125-250 m apart, although some horizons were autotracked in 3D. Horizon surfaces were generated from these mapped grids. Where the surfaces intersected dyke-induced faults, points were mapped on seismic lines orthogonal to the fault strikes every 125 along strike to define footwall and hanging wall cut-offs. The X, Y, and Z co-ordinates of all cut-off points was exported from Petrel and collated for each horizon using a bespoke python script that depth-converted their Z values (using data from Chandon-1, Chandon-2, Chandon-3, Investigator-1, and Yellowglen-1 borehole checkshots; https://www.ga.gov.au/nopims) and also calculated fault dip, throw, heave, and displacement between the pairs. These data were then passed through other bespoke scripts to: (1) collate all cut-off data for each fault; and (2) identify opposing cut-off pairs along the dyke-induced graben to calculate its width and predict the depth to the dyke top. These predictions were compared to depth-converted measured depths of dyke upper tips mapped in the seismic reflection data. For the pit craters, their plan-view outline was mapped on time-slices corresponding to their uppermost seismic expression; from these outlines, best-fit ellipses were generated and their long axis, short axis and area measurements extracted. The centre of each best-fit ellipse was characterised by a centroid, for which the X, Y, and Z data were noted. In addition to plan-view measurements, the height of the pit craters and their components were measured, as well as their height above underlying dykes or faults. These measured pit crater parameters were used to estimate pit crater volumes.