1. A multi-modal indirect approach Daniel P. Connelly 2009
Post presentation comments are in green
Age dating MAPCIS (Massive Australian Precambrian/Cambrian Impact Structure)
A multi-modal indirect approach
Daniel P. Connelly 2009
You will find background at MAPCIS.net
or at the GSA northeastern meeting March 2009 uploaded files, MAPCIS the Case for a Massive Australian Precambrian/Cambrian Impact Structure

2. Original Ring Discovery 2007
Discoveries are tangible measurable and not up for debate. Theories are explanations based on discoveries and are very much debatable.
Search moves from the general to specific, whether geographic area or age constraint.
Discovery Vs Theory
This discovery starts the search.
The search leads to new discoveries.
New discoveries propagate theories.

3. ~545 Ma
D. P. Connelly 2009

4. Impact Constraints Acraman Gosse Bluff 590Ma 142Ma 800km & 200km from MAPCIS center
Ejecta from Acraman does not cover MAPCIS
undisturbed
Gosse Bluff near the center is undisturbed and Acraman ejecta is not found over MAPCIS ejecta.
Rain over Gosse Bluff 2/2008

5. Alice Springs Orogeny Constraint ~450Ma
Deposited during Petermann orogeny
Uplifted during Alice Springs Orogeny
Mt. Currie Conglomerate
Mutijulu Arkose,i Ayers Rock
Deposited during Petermann Orogeny mya. Uplifted during Alice Springs Orogeny 450mya

6. Basement consistent with age?
This map is used as an example of the many 1:250,000 Geology maps used to cross check basement ages by examining exposed outcrops.
Although this 1954 map conforms with the 2008 GA Mafic Ultramafic map, there is considerable debate on the accuracy of these maps in this region.
Neoproterozoic ridges Kangaroo Island

7. MAFIC Events and MAPCIS Dating
Basic plate tectonics: When multiple events are divided, look for the youngest event to estimate the date of division. 13 29 11 10
MGr Moorilyanna Graben ~550Ma
ME29 Skipworth Event ~575
ME 26 Gairdner Event ~825
A26 Amata dyke swarm
G26 Gairdner dyke swarm
ME16 Curramulka Event ~1590
ME13 Woman in White Event ~1680
ME 11 Lunch Creek Event ~1750
ME10 Hart Event ~1780
ME 9 Mount Hay Event ~1810Ma 9
Tasman Gap 26
MGr 16 9
A26 10 11 29 26 13 16
G26
Derived from

8. Musgrave = Grenville age zircons
Zircon age diagram of suspected post impact proximal ejecta deposits
Worldwide Cambrian SS Enigma
Arenite
Distal
Grenville Age zircons
Feldspar local
A. Camacho et Al
Musgrave Provence = Impact Center
Over 120,000 Sq. Km
The enigma is solved, if one has a huge impact in the center of a Grenville Aged province. This is what appears to have happened.
Arkose
Conglomerate
P/C Boundary

9. Seven smaller impacts possibly coeval with MAPCIS
A cross check of impact age databases found this grouping of possibly coeval impacts, that appears to be associated with the predicted impact trajectory noted in dark blue .
All have evidence of a younger age constraint ~ at P/C boundary

10. Foelsche ~545Ma and Bukalara SS
Bukalara SS with shocked clasts blends into extensive regional unit.
Antrim Plateau Volcanics (Kalkarindji LIP) ~ Ma
Cover unlithified
Bukalara SS
After impact rapid burial
Infers a rapid sequence of impact, fill, and coverage by basalt.
Now
P.W. Haines &D.J. Rawlings 2001

11. MAPCIS Center Overview
Trajectory Northeast to Southwest
Radial Transpression Ridges ? Visible on 1:250, 000 Geology maps
PT Arcuate & Radial light blue
From Ayers Rock 1:250,000 Geology Map 2002
Largest known Pseudotachylite deposits, similar to Vredefort and Sudbury impacts.
1. Understand the locations shown on the next slide
Neoproterozoic Winnall, Inindia & Pinyinna beds of Mt. Conner appear to be missing from MAPCIS Center.

12. Mt. Frazer Radial Pseudotachylite
Edgoose CJ, Scrimgeour IR, Close DF 2003 Geology of the Musgrave Block, NT, NT Geological Survey Report 15
An example of PT not associated with a major fault.

13. Sampling Data from NT Geological Survey
There appears to be no attempt to date the pseudotachylite itself

14. Sample sites plotted on Google Earth
Sample B549
Derived from
Edgoose CJ, Scrimgeour IR, Close DF 2003 Geology of the Musgrave Block, NT, NT Geological Survey Report 15
Mt. Frazer

15. Sample B549 30km North of Mann Range pseudotachylite
Notable that these zircons have a metamorphic peak at 561ma , and zircon 13 exhibits a mosaic pattern.
Mosaic patterns in zircons has been associated with shock metamorphism.

16. Cumulative probability diagram of biotite ages for entire Musgrave Provence
Camacho et al., 2002
Inferred that all fault
systems in the Musgrave
Provence were activated
during the
the Petermann Orogeny.
120,000 square Km moved here and portions were exhumed from 40km deep.
Camacho All faults and shear zones were activated
Camacho et al., 2002

17. Conclusions
1. Precambrian Basement underlies all visible parts within the outer ring.
2. No known Precambrian impacts within 600km radius.
3. Ejecta from Acraman 590Ma does not overlay MAPCIS ejecta.
4. Gosse Bluff 142Ma and Alice Springs Orogeny structures are undisturbed.
5. Lower Cambrian layers, proximal and distal exhibit a Musgrave fingerprint.
6. Neoproterozoic beds appear to be missing from impact center.
7 . Moorilyanna Graben forms and the Tasman Gap opens syn-orgenic with Petermann Orogeny
8. Cambrian Bukalara SS fills and preserves Foelsche impact ~545mya.
9. Mass extinction of Ediacarans in Australia occurs at the end of Precambrian.
10. Dating of monazite and zircons nearest to pseudotachylite gives dates close to 545mya.
MAPCIS probably occurred just before the Precambrian/ Cambrian Boundary. Further research is needed to refine this dating.