Ediacaran carbonates in the Amadeus Basin, central Australia. A thesis submitted as partial fulfilment for the requirements of the University of Queensland.
School of Earth Sciences
C and O isotope stratigraphy of CryogenianEdiacaran carbonates in the Amadeus Basin, central Australia
A thesis submitted as partial fulfilment for the requirements of the University of Queensland School of Earth Sciences Honours programme
Isaac Schultz
Supervisor: Dr. Charles Verdel
Abstract Glacial and post-glacial sediments of Marinoan (~635 Ma) and Sturtian (~735 Ma) age are found across the world and are frequently correlated through C isotope stratigraphy, made possible in part due to unique isotopic signatures exhibited by post-glacial “cap carbonates”. This study generated a composite Neoproterozoic C isotope record of the Amadeus Basin in central Australia. An additional focus of the study was to explore the possibility of diachronous deposition of the Marinoan cap carbonate (Olympic Formation) in the Amadeus Basin. A prominent exposure of the Olympic Formation at Mt. Capitor in the eastern Amadeus Basin is lithologically distinct from most other exposures, suggesting differences in depositional environment. C isotope values from Mt. Capitor are also distinct and are consistent with diachronous cap deposition. In contrast, new C isotope data from other parts of the Cryogenian and Ediacaran stratigraphy of the Amadeus Basin show relatively little regional variation. The newly generated composite Neoproterozoic C isotope record from the Amadeus Basin has important similarities with the global record.
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Table of Contents 1
Introduction ........................................................................................................................ 6 1.1
Overview ..................................................................................................................... 6
1.2
Geological background ............................................................................................... 7
1.2.1
2
3
1.3
Carbon isotope stratigraphy ...................................................................................... 10
1.4
Cap carbonates .......................................................................................................... 11
Methods............................................................................................................................ 12 2.1
Stable isotope analysis .............................................................................................. 12
2.2
Whole-rock X-ray diffraction analysis ...................................................................... 13
Results .............................................................................................................................. 13 3.1
Olympic Formation ................................................................................................... 13
3.1.1
Type locality ...................................................................................................... 13
3.1.2
Mount Capitor .................................................................................................... 16
3.1.3
Ross River .......................................................................................................... 19
3.2
4
Basin structure ..................................................................................................... 8
Ringwood Member of the Aralka Formation ............................................................ 21
3.2.1
Ringwood Station............................................................................................... 21
3.2.2
Ellery Creek ....................................................................................................... 25
3.3
Limbla Member of the Aralka Formation ................................................................. 27
3.4
Star Bore .................................................................................................................... 29
Discussion ........................................................................................................................ 33 4.1
Correlating the Olympic Formation cap carbonate ................................................... 33
4.1.1 4.2
Correlating the Ringwood Member of the Aralka Formation ................................... 37
4.2.1 4.3
Potential for diachronous deposition of the Olympic Cap ................................. 35 Ellery Creek sections ......................................................................................... 40
Correlating the Limbla Member of the Aralka Formation ........................................ 42
4.3.1
Section IRR from Ross River Homestead ......................................................... 43
4.4
Potential for diagenetic alteration ............................................................................. 44
4.5
Comparison with global C isotope record ................................................................. 45
5
Conclusions ...................................................................................................................... 48
6
Acknowledgements .......................................................................................................... 48
7
References ........................................................................................................................ 49
8
Appendix .......................................................................................................................... 52 8.1
GPS data .................................................................................................................... 52
8.2
XRD plots.................................................................................................................. 52
8.3
Data tables ................................................................................................................. 57 3
Table of Figures Figure 1 Regional-scale map displaying sampling locations, and overlain isopachs that depict sediment thickness from the top of the Bitter Springs formation to the base of the Arumbera Sandstone (Figure 2). Data from Oaks Jr et al (1991) ............................................................... 6 Figure 2 Neoproterozoic strata within the Amadeus Basin. ..................................................... 8 Figure 3 Simplified outline of thrust sheets within the eastern Amadeus Basin, after Korsch and Lindsay (1989). ................................................................................................................... 9 Figure 4 Sampling locations plotted relative to eastern thrust sheets, after Stewart et al. (1991) ......................................................................................................................................... 9 Figure 5 The diachronous and isochronous models of cap carbonate deposition, after Hoffman (2007). ...................................................................................................................... 12 Figure 6 Type locality of the Olympic cap carbonate (Wells et al 1967) ............................... 14 Figure 7 Stratigraphic log and C and O isotope data for the Olympic Formation cap dolostone type locality section (IOT). ..................................................................................... 15 Figure 8 (A) Map illustrating the locations of sections 1ED and 2ED. (B) Layered strata at Mount Capitor. (C) Laminated, fine-grained dolomite turbidites. (D) Diamictite with granite, siltstone, carbonate, and sandstone clasts. Faceted clasts circled. Upper clast exhibits striations. .................................................................................................................................. 16 Figure 9 Stratigraphic log and C and O isotope data for section 1ED. Refer to Figure 6 for stratigraphic legend. ................................................................................................................. 17 Figure 10 XRD data plot. X-axis not to scale. ........................................................................ 18 Figure 11 Stratigraphic log and C and O isotope data for section 2ED. Refer to Figure 6 for stratigraphic legend. ................................................................................................................. 19 Figure 12 Sampling location of the IRR section. .................................................................... 20 Figure 13 Stratigraphic log and C and O isotope data for section IRR. Refer to Figure 6 for stratigraphic legend. ................................................................................................................. 20 Figure 14 Locations of sections IRMT, IRI, and 2RMTR. (B) Cross-bedding found throughout dolostones in sections IRMT and IRI. (C) A typical carbonate exposure. Orangetan weathering exposure, grey when fresh. (D) An example of a stromatolite found near the top of the section. ..................................................................................................................... 21 Figure 15 Stratigraphic log and C and O isotope data for section IRMT. Refer to Figure 6 for stratigraphic legend. ................................................................................................................. 22 Figure 16 Stratigraphic log and C and O isotope data for section IRI. Refer to Figure 6 for stratigraphic legend. ................................................................................................................. 23 Figure 17 Stratigraphic log and C and O isotope data for section 2RMTR. Note that the stratigraphic log for this section is a representative estimate. Refer to Figure 6 for stratigraphic legend. ................................................................................................................. 24 Figure 18 Stratigraphic log and C and O isotope data for section EC. Refer to Figure 6 for stratigraphic legend. ................................................................................................................. 25 Figure 19 Stratigraphic log and C and O isotope data for section 3EC. Refer to Figure 6 for stratigraphic legend. ................................................................................................................. 26 Figure 20 Stratigraphic log and C and O isotope data for section ILM. Refer to Figure 6 for stratigraphic legend. ................................................................................................................. 27 Figure 21 Stratigraphic log and C and O isotope data for section TRL. Refer to Figure 6 for stratigraphic legend. ................................................................................................................. 28 Figure 22 (A) Stromatolite from SB1. (B) Location of sections SB1 through SB3. (C) Red chert nodules found near the top of SB3 at a gradational contact. .......................................... 29
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Figure 23 Stratigraphic log and C and O isotope data for section SB1. Refer to Figure 6 for stratigraphic legend. Note that the stratigraphic log for this section is a representative estimate. ................................................................................................................................... 30 Figure 24 Stratigraphic log and C and O isotope data for section SB2. Refer to Figure 6 for stratigraphic legend. ................................................................................................................. 31 Figure 25 Stratigraphic log and C and O isotope data for section SB3. Refer to Figure 6 for stratigraphic legend. Note that the stratigraphic log for this section is a representative estimate. ................................................................................................................................... 32 Figure 26 δ13C plots for 1ED, 2ED, IOT, and SB3. Bottom right plot stretches 1ED to match the height of 2ED to illustrate similarity.................................................................................. 33 Figure 27 δ13C data from Marinoan cap carbonates (open symbols) and Sturtian cap carbonates (filled symbols; Kennedy et al., 1998). Triangles – Kalahari Craton. Circles – Congo craton. Diamonds – Amadeus Basin, Australia (134.6°E, 24°S) Note – this location is approximately 5.6 km from the sections 1ED and 2ED in this study. Sections normalised to 30 m. ........................................................................................................................................ 34 Figure 28 (after Halverson et al., 2005) - Post-Marinoan δ13C record data from Svalbard (open circles), northern Namibia (filled circles), and Oman (grey circles). ............................ 35 Figure 29 δ13C data from Kennedy et al. (2001 – supplementary data). Shaded green portions represent a lithology consistent with that of the cap dolostone. Unshaded sections represent interbedded shale/limestone sequences.................................................................................... 36 Figure 30 C and O isotope data for the Ringwood Member of the Aralka Formation, and its associated covariance plot........................................................................................................ 38 Figure 31 Suggested correlation for the obtained Ringwood Member data. Vertical scale uniform except for SB section. ................................................................................................ 41 Figure 32 C isotope data for the Limbla Member of the Aralka Formation, and its associated covariance plot. ........................................................................................................................ 42 Figure 33 Suggested correlation for sections TRL and ILM of the Limbla Member. Vertical scale uniform. ........................................................................................................................... 44 Figure 34 Composite profile for the Amadeus Basin compared to Halverson et al., (2005). Red data points are from this study.......................................................................................... 47
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1 Introduction 1.1 Overview The Neoproterozoic Era was marked by periods of widespread (perhaps global) glaciations (Hoffman et al 1998, Kirschvink 1992). The evidence for these glaciations are globallyoccurring glacial deposits that are overlain by “cap carbonates” (Hoffman et al 1998). Up to three separate Neoproterozoic glacial periods have been identified: the Sturtian (735 Ma), Marinoan (635 Ma), and Gaskiers (580 Ma), the ages of which are derived from U-Pb and Re-Os geochronology studies (Bowring et al 2003, Hoffmann et al 2004, Kendall et al 2006). Sturtian and Marinoan glacial units and their associated cap carbonates are exposed in various parts of the Amadeus Basin, in the southern part of the Northern Territory (Figure 1). The purpose of this study is to determine regional C isotope variability of some of these units, in particular the basal Ediacaran cap carbonate that overlies glaciogenic strata of the terminal Cryogenian Olympic Formation. An important outcome of the project is a composite C isotope record of the Neoproterozoic stratigraphy of the Amadeus Basin.
Figure 1 Regional-scale map displaying sampling locations, and overlain isopachs that depict sediment thickness from the top of the Bitter Springs formation to the base of the Arumbera Sandstone (Figure 2). Data from Oaks Jr et al (1991).
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1.2 Geological background The Areyonga Formation and the Olympic Formation (Figure 2) are the Sturtian and Marinoan glacial units, respectively, in the Amadeus Basin (Field 1991, Hoffmann et al 2004). Kennedy (1996) measured C isotope data from the type section of the Olympic Formation cap carbonate (blue shading in Figure 2) and found it to have average δ13C values of -3.8‰ and -5.0‰ at its base and top, respectively. While a useful benchmark, the study of Kennedy (1996) only investigated one section of the Olympic Cap. Carbon isotope values of carbonates inherently vary with palaeo-depth, however (Hollander & McKenzie 1991, Holser 1997, Schidlowski 1987), and previous studies suggest that palaeo-depth of the Olympic Cap may have been deposited in a range of environments (Shaw et al 1991, Walter et al 1995). These observations thus raise the possibility that there is regional variation in the δ13C composition of the Olympic cap carbonate. Additional complications include various nappes and thrust sheets in the NE part of the Amadeus Basin (Stewart et al 1991), particularly given that the Olympic cap type locality is located in the midst of several of these structures. In order to (1) shed light on regional variations of the Olympic Formation, (2) fully assess the extent of carbon isotope variations in the associated Olympic cap, and (3) develop a representative C isotope curve for the region, a suite of lithological and isotopic data has been collected from a range of sampling locations.
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Figure 2 Neoproterozoic strata within the Amadeus Basin.
1.2.1 Basin structure Shaw et al (1991) observed nine stratigraphic “megasequences” (1 – earliest, 9 – latest) in the Amadeus Basin that are separated by unconformities and defined either by intervals of renewed subsidence or changes in basin shape. The basin is split into northern and southern depozones bordered by a latitudinal central ridge, that is likely to be a basement horst or thrust block (Oaks Jr et al 1991). Sturtian and Marinoan glacial rocks form parts of depositional megasequences 3 and 4. During deposition of these megasequences, the primary depozone was located in the southern part of the basin. The depozones are thought to have been created as a result of thermal subsidence following an intracratonic rift phase (Korsch & Lindsay 1989). The Petermann Ranges orogeny subsequently terminated this configuration and shifted the primary depozone to the north at the end of the Proterozoic (Shaw et al 1991). 8
The eastern Amadeus Basin is marked by structures formed during a subsequent period of shortening approximately 450 My ago (Lindsay & Korsch 1989, Figure 3; Lindsay et al 1987, Walter et al 1995). These structures are shown in more detail in Figure 4 (Stewart et al 1991).
Figure 3 Simplified outline of thrust sheets within the eastern Amadeus Basin, after Korsch and Lindsay (1989).
Figure 4 Sampling locations plotted relative to eastern thrust sheets, after Stewart et al. (1991)
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1.3 Carbon isotope stratigraphy Carbon isotope stratigraphy can be useful for correlating carbonates over local-, regional-, and even global-scales (Holser 1997, Spero et al 1997). “Cap carbonates” generally have depleted δ13C values that approach -6‰ ± 1‰ δ13C (Hoffman et al 1998). Although carbonates from different Neoproterozoic basins often display variations in δ13C of roughly 1-3‰, variations in magnitude and trend are frequently consistent across basins within the same continent or on different continents (Halverson et al 2005a, Kennedy et al 2001, Narbonne et al 1994). δ13C is therefore highly useful as a tool for the correlation of Ediacaran and Cryogenian strata, especially when used in conjunction with lithological observations and other isotopic data such as Sr, S and O (Kaufman & Knoll 1995). While they are a useful tool for correlation, carbon isotope measurements are subject to local variation. A local departure in δ13C may suggest diachronous deposition or significant variation in seawater temperature (Hoffman et al 2009b). These variations introduce complications when attempting to use absolute C isotope values as a ‘benchmark’ for global correlations. Some units, such as the Wonoka Formation of South Australia, exhibit anomalously large δ13C excursions of -8‰ to -10‰ (Bjerrum & Canfield 2011, Derry 2010, Le Guerroué 2010). Explanations for these extreme isotopic excursions range from primary mechanisms such as methane release from clathrates (Bjerrum & Canfield 2011) to secondary mechanisms such as fluid-rock interaction during burial diagenesis (Derry 2010). Processes that influence δ13C of carbonates include the addition of a carbonate with a different isotopic composition, an influx of isotopically distinct fluids during recrystallisation, or decarbonation reactions (Kaufman & Knoll 1995). Decarbonation reactions in the presence of siliciclastic rocks (i.e. the reaction of carbonates, feldspars, or quartz to produce Mg- or Ca- silicates) will produce
13
C-enriched CO2, which lowers δ13C of the carbonates that
10
remain (Kaufman & Knoll 1995). Other mechanisms for δ13C variation include decreases in primary productivity, which will result in isotopically light δ13C of inorganic C due to the preferential incorporation of
12
C over
13
C into organic matter (Schidlowski 1987), and
changes in temperature (Hoffman et al 2009b).
1.4 Cap carbonates Cap carbonate deposition seems to require a rise in carbonate alkalinity (Grotzinger & Knoll 1995, Hoffman et al 1998, Kaufman & Knoll 1995). Three models attempting to explain cap carbonate formation have been proposed, and there is substantial variation between these models (Shields 2005). The first and most widely acknowledged is the Snowball Earth Hypothesis, which states that (1) increased carbonate alkalinity occurred due to continental runoff during glaciation; and (2) subsequent negative δ13C excursions are a reflection of 13C depletion as a by-product of increased continental silicate weathering (Hoffman et al 1998). The second theory relies on oceanic upwelling of anoxic, alkaline waters in a stratified ocean (Kaufman et al 1991). The third theory is centred on the destabilisation of methane clathrates as a mechanism for spurring deglaciation. Clathrate destabilisation would result in sulphate oxidation of methane on a large scale and a subsequent increase in carbonate alkalinity (Kennedy et al 2008). There are also three models that describe the detailed timing of post-glacial cap carbonate deposition (Hoffman et al 2007, Rose & Maloof 2010). In the so-called “isochronous model,” the bases and tops of cap carbonate are the same age up-section. Chemical variations must therefore then reflect changes in basin palaeochemistry over time. The second model, termed the semi-diachronous model, holds that the base cap carbonates are diachronous, while the tops are isochronous. This relationship may be due to interplay between meltwater plumes and glacial deep-water, causing a different mode of deposition during a glacio-eustatic flood
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(Hoffman et al 2007). The third model is diachronous cap deposition, in which both the bases and tops of caps vary in age according to their position within the basin (Hoffman et al 2007). In this scenario, a basin-wide change in seawater δ13C will be recorded at the top of the cap in a deep part of the basin, and at the bottom of the cap in a shallower part of the basin (Figure 5).
Figure 5 The diachronous and isochronous models of cap carbonate deposition, after Hoffman (2007).
2 Methods 2.1 Stable isotope analysis Due to the nature of exposure at each outcrop, sampling resolution is highly variable across the 12 measured sections. A total of 315 samples were collected over 12 days in the field. C and O isotopic analysis was conducted using an Isoprime Dual Inlet mass spectrometer with a Gilson autosampler at the University of Queensland’s Stable Isotope Geochemistry Laboratory (SIGL). Each sample was micro-drilled in order to avoid veins and visibly altered parts of the sample and to produce uniformly-sized fine powder for analysis. Carbonate powders were placed into 1 ml glass septa-vials and reacted with ~0.25 ml of H3PO4 at 90 °C for 1060 seconds. CO2 was purified with a cryogenic system and measured
12
relative to an in-house reference gas. Reproducibility of δ13C and δ18O results is estimated at ≤0.1‰ based on repeated measurements of internal standards.
2.2 Whole-rock X-ray diffraction analysis X-ray diffraction (XRD) analysis was undertaken using a Druker D8 Advance X-ray Powder Diffractometer at the University of Queensland Centre for Microscopy and Microanalysis (CMM). Each sample was powdered with a FRITISCH Pulverisette 13 Disk Mill. The mill was cleaned with ethanol before each sample was processed. Each milling run produced approximately 7 g of sample. Approximately 6 g was back-loaded into a sample-holder and firmly tamped down using sterilised glass to ensure a homogenous, flat surface with a reduced possibility of preferred grain orientation. Nine samples were selected for X-ray diffraction analysis. The selection criteria were (1) the samples were broadly representative of at least one section; and (2) the results could be used to corroborate field observations regarding rock type. The section chosen for analysis was 1ED, a section of the Olympic cap that is dominantly dolomitic, with the exception of limestone beds at the top of the section.
3 Results 3.1 Olympic Formation 3.1.1 Type locality The type locality of the Olympic Formation is situated in the eastern Amadeus Basin (Wells et al 1967; Figure 6). At this location, the Olympic cap carbonate is made up of fine-grained dolostone, brown where weathered, and grey when fresh. There are few, if any, distinguishing sedimentary features to be found at the type locality. Beds of 5-10 cm
13
thickness occur in the upper half of the section. There is no exposed contact with underlying units.
Figure 6 Type locality of the Olympic cap carbonate (Wells et al 1967)
Kennedy (1996) described a series of four distinct lithofacies over a 4 m section at the type locality. However, no such sedimentary features were found during this study. It appears likely that the data ascribed to the type section by Kennedy (1996) belong to another location. 24 samples were collected at the type locality. δ13C values are roughly -1‰ at the base of the section and decline to about -3 to -4 ‰ at the top (Figure 7). δ18O values also decline upsection.
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Figure 7 Stratigraphic log and C and O isotope data for the Olympic Formation cap dolostone type locality section (IOT).
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3.1.2 Mount Capitor Mount Capitor is a key location in the NE part of the basin, approximately 26 km northeast of Santa Teresa (Figures 1 and 4). It is approximately 100 m in height and is made up of quartzite, diamictite, dolostone and limestone. Up to 2 m of Olympic Formation diamictite is exposed above quartzite beds of the same formation (Figure 8B). The diamictite includes an assortment of granite, carbonate, siltstone and sandstone clasts that range in size from approximately 5 mm to 500 mm in diameter (Figure 8D).
Figure 8 (A) Map illustrating the locations of sections 1ED and 2ED. (B) Layered strata at Mount Capitor. (C) Laminated, fine-grained dolomite turbidites. (D) Diamictite with granite, siltstone, carbonate, and sandstone clasts. Faceted clasts circled. Upper clast exhibits striations.
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The Olympic cap dolostone is made up of turbidites at Mount Capitor (Figure 8C). The majority of the cap is comprised of dolomitic turbidites, though the top of the cap is made up of limestone (Figures 9 and 10). A total of 84 samples were collected between the two sections (1ED and 2ED) at this location. Carbon and oxygen isotope values are relatively heavy at the base of each section and progress toward lighter values up section. XRD measurements were also made for samples from this location (Figure 10; Table 1).
Figure 9 Stratigraphic log and C and O isotope data for section 1ED. Refer to Figure 6 for stratigraphic legend.
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Figure 10 XRD data plot. X-axis not to scale.
Table 1 Relative percentages of quartz, dolomite, and calcite from selected 1ED samples.
Stratigraphic height (m) 3.35 14 18 24 30.3 34 37.5 38 38.3
Quartz (%) 19.76 14.61 10.18 7.15 8.45 9.44 6.45 4.67 8.77
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Dolomite (%) 80.24 85.39 89.82 92.85 91.55 90.56 1.71 0 0
Calcite (%) 0 0 0 0 0 0 91.84 95.33 91.23
Figure 11 Stratigraphic log and C and O isotope data for section 2ED. Refer to Figure 6 for stratigraphic legend.
3.1.3 Ross River A small outcrop of carbonate approximately 1 km north of the Ross River homestead was also investigated (Figures 1 and 12). This outcrop is comprised primarily of dolostone and contains 5 mm to 300 mm clasts of carbonates and siliciclastics. Carbon and oxygen isotope data from six samples across this section are presented in Figure 13. Although the measured section is only 0.3 m in height due to limited exposure, there is a clear up-section trend in the data toward lighter carbon and oxygen isotope values.
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Figure 12 Sampling location of the IRR section.
Figure 13 Stratigraphic log and C and O isotope data for section IRR. Refer to Figure 6 for stratigraphic legend.
20
3.2 Ringwood Member of the Aralka Formation 3.2.1 Ringwood Station Ringwood Station is located approximately 110 km E of Alice Springs (Figure 1). The Ringwood Member comprises the base of the Aralka Formation (Figure 2). It is primarily made up of dolostone and limestone (Figure 14C) and is characterised by wave ripples and stromatolites (Figure 14B, D).
Figure 14 Locations of sections IRMT, IRI, and 2RMTR. (B) Cross-bedding found throughout dolostones in sections IRMT and IRI. (C) A typical carbonate exposure. Orange-tan weathering exposure, grey when fresh. (D) An example of a stromatolite found near the top of the section.
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77 samples were collected from three sections of the Ringwood Member that are spread out over approximately 32 km in the Ringwood Station locality (Figure 14A). Figures 15 through 17 illustrate carbon and oxygen isotope data for these sections. The data are isotopically heavy and display no discernible trend. Values in 2RMTR are markedly lighter at the base of the section compared to those at the base of the IRMT and IRI sections.
Figure 15 Stratigraphic log and C and O isotope data for section IRMT. Refer to Figure 6 for stratigraphic legend.
22
Figure 16 Stratigraphic log and C and O isotope data for section IRI. Refer to Figure 6 for stratigraphic legend.
23
Figure 17 Stratigraphic log and C and O isotope data for section 2RMTR. Note that the stratigraphic log for this section is a representative estimate. Refer to Figure 6 for stratigraphic legend.
24
3.2.2 Ellery Creek The Ellery Creek (EC and 3EC) sampling locations are approximately 80 km west of Alice Springs (Figure 1). EC is primarily comprised of orange-grey carbonate and sandstone interbedded with conglomerate. The vast majority of clasts at this location are carbonate, with lesser amounts of siliciclastic and basement clasts. Exposure is generally poor along the EC section. Minor coarsening-upwards sequences are found in the middle of the section. The 3EC section includes a yellow-grey carbonate unit that is exposed over 7 m of section. C and O isotope data from 18 samples across both sections are shown in Figures 18 and 19.
Figure 18 Stratigraphic log and C and O isotope data for section EC. Refer to Figure 6 for stratigraphic legend.
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Figure 19 Stratigraphic log and C and O isotope data for section 3EC. Refer to Figure 6 for stratigraphic legend.
26
3.3 Limbla Member of the Aralka Formation The Limbla Member of the Aralka Formation was first named by Wells et al (1967). It immediately underlies the Olympic Formation and is comprised of calcarenite limestone and dolostone, interbedded with sandstone. Festooned cross-bedding is a characteristic sedimentary feature of this unit and is observed in both the limestone and dolostone units throughout the ILM and TRL sections (Figures 20 through 21).
Figure 20 Stratigraphic log and C and O isotope data for section ILM. Refer to Figure 6 for stratigraphic legend.
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Figure 21 Stratigraphic log and C and O isotope data for section TRL. Refer to Figure 6 for stratigraphic legend.
The sections TRL and ILM are located southeast of Alice Springs (Figure 1), and are separated by approximately 41 km. Figures 20 and 21 display isotope data for 52 samples from these sections. The data show that C isotope values are extremely heavy throughout this unit.
28
3.4 Star Bore Star Bore (SB) is a 1040 m thick section located 95 km southeast of Alice Springs (Figure 1). It includes three main exposed sub-sections and is comprised of stromatolites, carbonate cements, coarsening-upwards sequences, and red chert inclusions (Figures 22A and C). It is primarily composed of grey and tan dolostone, with siltstone laminations at the base. Carbon and oxygen isotope data from 61 samples for the entire 1040 m section are presented in Figures 23 through 25. The SB section will be split into three components named SB1, SB2, and SB3.
Figure 22 (A) Stromatolite from SB1. (B) Location of sections SB1 through SB3. (C) Red chert nodules found near the top of SB3 at a gradational contact.
29
Figure 23 Stratigraphic log and C and O isotope data for section SB1. Refer to Figure 6 for stratigraphic legend. Note that the stratigraphic log for this section is a representative estimate.
30
Figure 24 Stratigraphic log and C and O isotope data for section SB2. Refer to Figure 6 for stratigraphic legend.
31
Figure 25 Stratigraphic log and C and O isotope data for section SB3. Refer to Figure 6 for stratigraphic legend. Note that the stratigraphic log for this section is a representative estimate.
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4 Discussion 4.1 Correlating the Olympic Formation cap carbonate Stable isotope data The C and O isotope data for the Olympic Formation cap dolostone are from sections IOT, 1ED, 2ED, and SB3. Figure 26 plots C isotope data from these sections on the same graph.
Figure 26 δ13C plots for 1ED, 2ED, IOT, and SB3. Bottom right plot stretches 1ED to match the height of 2ED to illustrate similarity.
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C isotope data from post-Marinoan cap carbonates frequently form a distinctive curve that includes a steady decline in δ13C, with no recovery at the top of the section to positive values (Figure 27; Kennedy et al. 1998).
Figure 27 δ13C data from Marinoan cap carbonates (open symbols) and Sturtian cap carbonates (filled symbols; Kennedy et al., 1998). Triangles – Kalahari Craton. Circles – Congo craton. Diamonds – Amadeus Basin, Australia (134.6°E, 24°S) Note – this location is approximately 5.6 km from the sections 1ED and 2ED in this study. Sections normalised to 30 m.
Both 1ED and 2ED have exposed contacts with over- and underlying strata. There is a clear up-section ~5‰ shift toward lighter C isotope values in both 1ED and 2ED, a pattern that may be indicative of an overall increase in temperature during deposition across both sections (Hoffman et al 2007, Hoffman & Macdonald 2010). IOT exhibits the same trend, while SB3 does not appear to show any trend, although it exhibits negative C isotope values associated with the top of a cap carbonate. The data in Figure 28 are further evidence of this post-Marinoan trend, with isotope values shifting toward negative values and terminating at values of approximately -5‰. The recovery toward 0‰ occurs in the overlying rhythmite succession. An increase in
34
temperature may be responsible for the gradual decline in δ13C values observed globally as an increase in temperature would be expected after a period of glacial melting.
Figure 28 (after Halverson et al., 2005) - Post-Marinoan δ13C record data from Svalbard (open circles), northern Namibia (filled circles), and Oman (grey circles).
4.1.1 Potential for diachronous deposition of the Olympic Cap The δ13C data collected from the Olympic cap in this study share most of the attributes previously determined to be associated with Marinoan cap carbonates (Figure 26). However, the most complete sections (1ED and 2ED) record markedly heavier isotope values at their base than sections from other locations. Previous data from the Amadeus Basin can assist in assessing why this is the case. Additional data for the Olympic cap dolostone is provided by Kennedy et al (2001) from the Cleary Creek and Hale River localities (Figure 29). These sections record negative δ13C values at their base and decline to approximately -3.5‰ in the cap dolostone portions of each section. The recovery to 0‰ in an interbedded shale/limestone lithology is consistent with that observed by Halverson et al. (2005) in Figure 28. 35
Both the Cleary Creek and Hale River sites are within the Camel Flat thrust sheet, an allochthonous part of the basin, while the Olympic Cap locations sampled in this study are within the autochthonous part of the basin (Figure 4). There is evidence that allochthonous thrust sheets were shifted 60-70 km to the south in the Late Ordovician during the Alice Springs Orogeny (Stewart et al 1991). Given that the Cleary Creek and Hale River sampling locations are within one of these sheets, it is possible that both locations were originally up to 60 km farther north.
Figure 29 δ13C data from Kennedy et al. (2001 – supplementary data). Shaded green portions represent a lithology consistent with that of the cap dolostone. Unshaded sections represent interbedded shale/limestone sequences.
Isopach data from Oaks Jr et al. (1991) constrain total sediment thickness from the beginning of the deposition of the Bitter Springs formation (750 Ma) to the end of the deposition of the Arumbera Sandstone (530 Ma; Walter et al 1995). The Cleary Creek and Hale River sections would therefore have been deposited in a relatively thin part of the basin, presumably in a shallow environment. Conversely, sections 1ED and 2ED are located in an autochthonous
36
part of the basin associated with a thick sedimentary succession, suggesting that they were deposited in a more distal part of the basin. Furthermore, lithological characteristics of the dolostone at Mount Capitor suggest a deeper water setting (Figure 7). These features were unique to the Mount Capitor location among the surveyed sections. Due to basin geometry, it is possible that the Olympic cap carbonate was deposited diachronously (Figure 5). If so, the Mount Capitor sections represent a relatively early period of post-Marinoan deglaciation. X-ray diffraction data X-ray diffraction data for nine samples from the 1ED section corroborate field observations that there is a dolostone-limestone transition at the top of the cap. This is typical of cap carbonates from other localities (Fairchild & Kennedy 2007, Hoffman et al 2009a, Hoffman et al 1998, Sawaki et al 2010). The transition is coupled with a shift in isotope values, which is likely to indicate a significant change in seawater chemistry during the period.
4.2 Correlating the Ringwood Member of the Aralka Formation C and O isotope data for the Ringwood Member of the Aralka Formation come from the sections IRMT, IRI, 2RMTR, SB2-1, and SB2-2, which are plotted together in Figure 30. The Ringwood Member data are significantly varied. This is in part because (1) the sections are at least 10 km from each other, (2) there is varied sampling resolution in these sections due to cover, and most importantly (3) the bases of some sections (namely IRMT, IRI, SB2-1 and SB2-2) were not exposed. These four sections must therefore be put into context relative to sections (2RMTR, SB1) where the contact with the underlying Areyonga Formation is exposed.
37
Figure 30 C and O isotope data for the Ringwood Member of the Aralka Formation, and its associated covariance plot.
Figure 31 places each Ringwood Member section into context relative to previous data from Walter et al (2000). Given that the bases of sections IRI, IRMT, SB2-1 and SB2-2 are not exposed and that there are no distinct reproducible anomalies between these sections, Figure 31 outlines a tentative correlation. The vertical scale has been preserved in each section. The base of section 2RMTR coincides with the contact with the underlying Areyonga Formation, so the base of this section is regarded as a Sturtian cap. C isotope values 38
immediately overlying the Areyonga Formation are -4.7‰ (Figure 31 – blue shading) and become gradually heavier up-section, though there is a small negative spike to -3‰ at 82 m (Figure 31 – red shading). Such a recovery from light values is expected following the Areyonga glaciation (Walter et al 2000), likely due to the resumption of primary biological productivity (Holser 1997). Similarly, the base of SB1 records a negative C isotope value at its base of -3.6‰. It then experiences a spike back to a negative value of -4.2‰ at approximately 50 m, followed by a shift toward 0‰. Each of the other Ringwood sections is characterised by generally positive carbon isotope values of approximately 3‰ (IRMT, SB2-1, SB2-2, IRI). Previous data from Walter et al (2000) from the Limbla Syncline are largely similar to this from 220-450 m. However, the IRI section records markedly lighter carbon isotope values at its base compared to IRMT, so IRMT is shifted accordingly. A noticeable omission in the SB section is the Limbla Member of the Aralka Formation. Given that the Limbla Member conformably overlies the Ringwood Member, it is possible that either (1) the Limbla Member was not deposited at this location or (2) the Limbla Member was eroded at this location. Low-angle cross-bedding is observed in many of the Ringwood Member sections (Figures 12 through 15), which is a feature typically associated with a shallow-water depositional environment above wave-base. The appearance of stromatolites (Figure 12D) is further evidence of a shallow marine palaeoenvironment. Sections IRI and 2RMTR are both within the Olympic thrust sheet (Stewart et al 1991). Assuming, as before, that the thrust sheet travelled approximately 60 km south during the Palaeozoic and using the same interpretive model as before, one would expect to see lighter values in these sections. However, this is not the case, suggesting that the entirety of the 39
Ringwood Formation was deposited synchronously throughout the basin. The presence of cross-bedding in each Ringwood Member section supports this. 4.2.1 Ellery Creek sections The base of the EC section corresponds lithologically with a transition between dolostone of the Bitter Springs Formation and diamictite-conglomeratic facies of the overlying Areyonga Formation (Figure 18; Wells et al 1967). Insufficient isotope data were collected to confirm this, although isotopic values do shift toward 2‰ in the latter Ringwood Member part of the section, similar to values from IRI, IRMT, SB2-1 and SB2-2. The EC3 section records positive isotope values of approximately 2‰ and is situated in a largely covered area where the Ringwood Member is expected. Given that the EC section is sampled at a low resolution and 3EC could correlate with several sections of the available data, the sections EC3 and EC were not included in the Figure 31 correlation.
40
Figure 31 Suggested correlation for the obtained Ringwood Member data. Vertical scale uniform except for SB section.
41
4.3 Correlating the Limbla Member of the Aralka Formation C and O isotope data for the Limbla Member of the Aralka Formation are from sections ILM and TRL, which are plotted together in Figure 32.
Figure 32 C isotope data for the Limbla Member of the Aralka Formation, and its associated covariance plot.
Carbon isotope values from the Limbla Member are uniformly heavy, in accordance with data from four previous samples from Kennedy et al. (2001). The Limbla Member was deposited after the 500 m thick Ringwood Member. The generally heavy isotope values observed are realistic given that (1) the environment of deposition is likely to be shallow 42
marine, which is favoured by biological producers; and (2) millions of years would have passed since the Areyonga glaciation, making such a recovery possible. At the base of the ILM section, a contact between the Limbla Member and a siltstone unit that overlies the Ringwood Member was observed, but no comparable contact was observed at the base of TRL. A stratigraphic comparison coupled with C isotope data is illustrated in Figure 33. There is a sequence of laminated dolostone and siltstone with carbonate clasts and cross-bedding over approximately 10 m in both sections, corresponding with a δ13C peak at 10‰ (green shading in Figure 33). The disappearance of clasts and laminations in the dolostone outcrop following this peak suggests synchronous deposition when correlating by lithology, although ILM does not include the same sandstone-conglomerate as TRL, which may be due to cover. 4.3.1 Section IRR from Ross River Homestead The IRR section contains samples with slightly positive carbon isotope values (mean values of 5.9‰; Figure 11), which decline by 1.6‰ over 30 cm. The outcrop, which consists of carbonate and siliclastic breccias overlain by dolostone, has previously been correlated with the Olympic Formation and Olympic cap (Skotnicki et al 2008). However, the C isotope data collected in this study do not support that conclusion because δ13C values of the IRR “cap” are distinctly greater than for any other known example of a Marinoan cap carbonate. When partnered with lithological and stratigraphic observations, these data suggest that the IRR strata are a part of the Bitter Springs Formation, rather than the Olympic Formation.
43
Figure 33 Suggested correlation for sections TRL and ILM of the Limbla Member. Vertical scale uniform.
4.4 Potential for diagenetic alteration Given that the samples analysed in this study are over 600 My old, it is highly likely that they have undergone significant fluid-rock interaction; further to this, some workers maintain that all Neoproterozoic rocks have undergone significant alteration (Knauth & Kennedy 2009). Covariance between δ13C and δ18O can be used to assess the extent of diagenetic alteration. A significant trend is indicative of alteration. However, many studies have addressed the issue of diagenetic alteration in carbonates and have found that original δ13C signatures are often 44
maintained even following diagenesis (Derry et al 1992, Kaufman et al 1991, Kaufman & Knoll 1995). Given the positive covariation between δ13C and δ18O in samples from 1ED and 2ED (Figure 24), it is possible that the Olympic cap carbonate sediments were diagenetically altered in a marine-meteoric mixing-zone environment at Mount Capitor (Allan & Matthews 1982, Moore 1989). However, (1) there are no abrupt, significant departures in δ18O from δ13C; and (2) there are global correlative records which corroborate the values observed in these data. It is therefore unlikely that diagenesis accounts for the major δ13C variations described above. There is little covariance between δ18O and δ13C in the Ringwood Member sections, signalling that significant diagenetic alteration is unlikely. In addition, the preservation of unaltered microstructures such as cross-bedding and stromatolites at mm-scale suggests minimal disruption of these units. However, the data are somewhat scattered, which is attributable to the varied sampling resolution of each section. There are often 20 m gaps in the data due to cover, and it has been demonstrated that δ13C can record secular variation of more than 1.6‰ over a 30 cm interval (Figure 11). The same can be said of the Limbla Member sections.
4.5 Comparison with global C isotope record A composite isotope curve detailing carbon isotope variation in each unit is presented in Figure 34 and compared to the global profile compiled by Halverson et al (2005b). This record is, to quote Halverson et al., “based unavoidably on interpretive correlations.” The Bitter Springs Formation data from Swanson-Hysell et al (2010) bear a strong resemblance to the data from Svalbard. The new Ringwood Member data from this study correlate with the positive portion of previous data from Walter et al (2000). A lack of under- and overlying contacts due to cover are a likely cause for the omissions of the negative and positive trends 45
in data from the Limbla Syncline data. The Limbla Member data are distinctively heavy and align well with the Namibian data. The beginning of a trend toward lighter values is observed in the new data, which is mirrored by that from Namibia. The Olympic cap carbonate data from this study records the same negative peak at -5‰ as the Namibia data, but records significantly heavier values at its base, which may be attributable to diachronous deposition. The overall similarity between the two records indicates that C isotopes are a viable tool for correlation between Neoproterozoic carbonates. Shifts in the curve are likely to be caused by steady-state changes in the balance of the Neoproterozoic carbon cycle, represented by the fraction of dissolved inorganic carbon (DIC) in the Neoproterozoic ocean (Johnston et al 2012, Swanson-Hysell et al 2012, Swanson-Hysell et al 2010), and moderated by episodic influxes of isotopically light C, rather than diagenetic alteration or other such localised phenomena.
46
Figure 34 Composite profile for the Amadeus Basin compared to Halverson et al., (2005). Red data points are from this study.
47
5 Conclusions The lithology of the Olympic Formation cap varies within the Amadeus Basin, suggesting differences in depositional environment. Some of these differences seem to be related to position within thrust sheets or autochthonous parts of the basin. These observations suggest that the Olympic Formation cap carbonate was deposited diachronously. Carbon isotope profiles reflect diachronous deposition between relatively deep-water, autochthonous locations versus relatively shallow-water, allochthonous locations for this unit. In contrast, clear lithological variations were not observed for measured sections of the Ringwood Member of the Aralka Formation, and there are also no clear δ13C shifts between these sections. These findings suggest that the Ringwood Member was deposited isochronously or nearly isochronously across the basin. Carbonates of the Limbla Member of the Aralka Formation record heavy, steadily declining carbon isotope values and sedimentary structures indicative of shallow water deposition in a relatively high-energy environment. The Limbla Member also appears to have been deposited isochronously across a wide portion of the basin. C isotope profiles from carbonates in the Amadeus Basin adhere to those from equivalent units found globally, further refining the global C isotope record for the late Neoproterozoic.
6 Acknowledgements I would like to thank the following people: Jacqui Wong and Anya Yago for their assistance with the XRD analysis; Sue Golding and Kim Baublys for helping with the stable isotope laboratory equipment; Reena Joubert for help with field observations; my fellow Honours students for general upkeep of morale; and last but certainly not least, Dr. Charles Verdel for his mentorship and continued support throughout the year. 48
7 References Allan J, Matthews R. 1982. Isotope signatures associated with early meteoric diagenesis. Sedimentology 29: 797-817 Bjerrum CJ, Canfield DE. 2011. Towards a quantitative understanding of the late Neoproterozoic carbon cycle. Proceedings of the National Academy of Sciences 108: 5542-7 Bowring S, Myrow P, Landing E, Ramezani J, Grotzinger J. 2003. Geochronological constraints on terminal Neoproterozoic events and the rise of Metazoan. Presented at EGS-AGU-EUG Joint Assembly Derry LA. 2010. A burial diagenesis origin for the Ediacaran Shuram–Wonoka carbon isotope anomaly. Earth and Planetary Science Letters 294: 152-62 Derry LA, Kaufman AJ, Jacobsen SB. 1992. Sedimentary cycling and environmental change in the Late Proterozoic: evidence from stable and radiogenic isotopes. Geochimica et Cosmochimica Acta 56: 1317-29 Fairchild IJ, Kennedy MJ. 2007. Neoproterozoic glaciation in the Earth System. Journal of the Geological Society 164: 895-921 Field B. 1991. Paralic and periglacial facies and contemporaneous deformation of the late Proterozoic Olympic Formation, Pioneer Sandstone, and Gaylad Sandstone, Amadeus Basin, central Australia. Geological and Geophysical Studies in the Amadeus Basin, Central Australia, Bulletin 236 1: 127-36 Grotzinger JP, Knoll AH. 1995. Anomalous carbonate precipitates: is the Precambrian the key to the Permian? Palaios 10: 578-96 Halverson GP, Hoffman PF, Schrag DP, Maloof AC, Rice AHN. 2005a. Toward a Neoproterozoic composite carbon-isotope record. Geological Society of America Bulletin 117: 1181 Halverson GP, Hoffman PF, Schrag DP, Maloof AC, Rice AHN. 2005b. Toward a Neoproterozoic composite carbon-isotope record. Geological Society of America Bulletin 117: 1181-207 Hoffman PF, Calver CR, Halverson GP. 2009a. Cottons Breccia of King Island, Tasmania: Glacial or non-glacial, Cryogenian or Ediacaran? Precambrian Research 172: 311-22 Hoffman PF, Calver CR, Halverson GP. 2009b. Cottons Breccia of King Island, Tasmania: Glacial or non-glacial, Cryogenian or Ediacaran? Precambrian Research 172: 311-22 Hoffman PF, Halverson GP, Domack EW, Husson JM, Higgins JA, Schrag DP. 2007. Are basal Ediacaran (635 Ma) post-glacial “cap dolostones” diachronous? Earth and Planetary Science Letters 258: 114-31 Hoffman PF, Kaufman AJ, Halverson GP, Schrag DP. 1998. A Neoproterozoic snowball earth. Science 281: 1342-6 Hoffman PF, Macdonald FA. 2010. Sheet-crack cements and early regression in Marinoan (635Ma) cap dolostones: Regional benchmarks of vanishing ice-sheets? Earth and Planetary Science Letters 300: 374-84 Hoffmann K-H, Condon D, Bowring S, Crowley J. 2004. U-Pb zircon date from the Neoproterozoic Ghaub Formation, Namibia: constraints on Marinoan glaciation. Geology 32: 817-20 Hollander DJ, McKenzie JA. 1991. CO2 control on carbon-isotope fractionation during aqueous photosynthesis: A paleo-pCO2 barometer. Geology 19: 929-32 Holser W. 1997. Geochemical events documented in inorganic carbon isotopes. Palaeogeography, Palaeoclimatology, Palaeoecology 132: 173-82
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Johnston D, Macdonald F, Gill B, Hoffman P, Schrag D. 2012. Uncovering the Neoproterozoic carbon cycle. Nature 483: 320-3 Kaufman AJ, Hayes J, Knoll AH, Germs GJ. 1991. Isotopic compositions of carbonates and organic carbon from upper Proterozoic successions in Namibia: stratigraphic variation and the effects of diagenesis and metamorphism. Precambrian Research 49: 301-27 Kaufman AJ, Knoll AH. 1995. Neoproterozoic variations in the C-isotopic composition of seawater: stratigraphic and biogeochemical implications. Precambrian Research 73: 27-49 Kendall B, Creaser RA, Selby D. 2006. Re-Os geochronology of postglacial black shales in Australia: Constraints on the timing of “Sturtian” glaciation. Geology 34: 729 Kennedy M, Mrofka D, von der Borch C. 2008. Snowball Earth termination by destabilization of equatorial permafrost methane clathrate. Nature 453: 642-5 Kennedy MJ. 1996. Stratigraphy, sedimentology, and isotopic geochemistry of Australian Neoproterozoic postglacial cap dolostones: deglaciation, d13C excursions, and carbonate precipitation. Journal of Sedimentary Research 66 Kennedy MJ, Christie-Blick N, Prave AR. 2001. Carbon isotopic composition of Neoproterozoic glacial carbonates as a test of paleoceanographic models for snowball Earth phenomena. Geology 29: 1135 Kirschvink JL. 1992. Late Proterozoic low-latitude global glaciation: the snowball Earth. Knauth LP, Kennedy MJ. 2009. The late Precambrian greening of the Earth. Nature 460: 728-32 Korsch R, Lindsay J. 1989. Relationships between deformation and basin evolution in the intracratonic Amadeus Basin, central Australia. Tectonophysics 158: 5-22 Le Guerroué E. 2010. Duration and synchroneity of the largest negative carbon isotope excursion on Earth: The Shuram/Wonoka anomaly. Comptes Rendus Geoscience 342: 204-14 Lindsay JF, Korsch R. 1989. Interplay of tectonics and sea-level changes in basin evolution: an example from the intracratonic Amadeus Basin, central Australia. Basin Research 2: 3-25 Lindsay JF, Korsch R, Wilford JR. 1987. Timing the breakup of a Proterozoic supercontinent: evidence from Australian intracratonic basins. Geology 15: 1061-4 Moore CH. 1989. Carbonate diagenesis and porosity: Elsevier Narbonne GM, Kaufman AJ, Knoll AH. 1994. Integrated chemostratigraphy and biostratigraphy of the Windermere Supergroup, northwestern Canada: Implications for Neoproterozoic correlations and the early evolution of animals. Geological Society of America Bulletin 106: 1281-92 Oaks Jr RQ, Deckelman JA, Conrad K, Hamp L, Phillips J, Stewart A. 1991. Sedimentation and tectonics in the northeastern and central Amadeus Basin, central Australia. Geological and Geophysical Studies in the Amadeus Basin, Central Australia, Bulletin 236 1: 73-90 Rose CV, Maloof AC. 2010. Testing models for post-glacial ‘cap dolostone’ deposition: Nuccaleena Formation, South Australia. Earth and Planetary Science Letters 296: 165-80 Sawaki Y, Ohno T, Tahata M, Komiya T, Hirata T, et al. 2010. The Ediacaran radiogenic Sr isotope excursion in the Doushantuo Formation in the Three Gorges area, South China. Precambrian Research 176: 46-64 Schidlowski M. 1987. Application of stable carbon isotopes to early biochemical evolution on Earth. Annual Review of Earth and Planetary Sciences 15: 47
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Shaw R, Etheridge M, Lambeck K. 1991. Development of the Late Proterozoic to Mid‐ Paleozoic, intracratonic Amadeus Basin in central Australia: A key to understanding tectonic forces in plate interiors. Tectonics 10: 688-721 Shields GA. 2005. Neoproterozoic cap carbonates: a critical appraisal of existing models and the plumeworld hypothesis. Terra Nova 17: 299-310 Skotnicki SJ, Hill AC, Walter M, Jenkins R. 2008. Stratigraphic relationships of Cryogenian strata disconformably overlying the Bitter Springs Formation, northeastern Amadeus Basin, Central Australia. Precambrian Research 165: 243-59 Spero HJ, Bijma J, Lea DW, Bemis BE. 1997. Effect of seawater carbonate concentration on foraminiferal carbon and oxygen isotopes. Nature 390: 497-500 Stewart A, Oaks Jr RQ, Deckelman JA, Shaw RD. 1991. Mesothrust versus megathurst interpretations of the structure of the northeastern Amadeus Basin, central Australia. Geological and Geophysical Studies in the Amadeus Basin, Central Australia, Bulletin 236 1: 361-83 Swanson-Hysell NL, Maloof AC, Kirschvink JL, Evans DAD, Halverson GP, Hurtgen MT. 2012. Constraints on Neoproterozoic paleogeography and Paleozoic orogenesis from paleomagnetic records of the Bitter Springs Formation, Amadeus Basin, central Australia. American Journal of Science 312: 817-84 Swanson-Hysell NL, Rose CV, Calmet CC, Halverson GP, Hurtgen MT, Maloof AC. 2010. Cryogenian glaciation and the onset of carbon-isotope decoupling. Science 328: 60811 Walter M, Veevers J, Calver C, Gorjan P, Hill A. 2000. Dating the 840–544 Ma Neoproterozoic interval by isotopes of strontium, carbon, and sulfur in seawater, and some interpretative models. Precambrian Research 100: 371-433 Walter M, Veevers J, Calver C, Grey K. 1995. Neoproterozoic stratigraphy of the Centralian Superbasin, Australia. Precambrian Research 73: 173-95 Wells A, RANFORD L, Stewart A, COOK P. 1967. t~ SHAW, RD, 1967. The geology of the northeastern part of the Amadeus Basin, Northern Territory. Rep. Bur. Miner. Resour. Geol. Geophys. Aust. II3
51
8 Appendix 8.1 GPS data Waypoint IOT
Latitude
Longitude
Elevation (m)
Description
-23.9024
134.99338
377
Olympic Fm, Ringwood Station, type locality
IRMT
-23.88444
135.01514
416
Ringwood Mbr,Ringwood Station, type locality, base of section
ILM
-23.88421
135.00688
413
Limbla Mbr, Ringwood Station, top of section
IRI
-23.9374
134.94919
378
Ringwood Mbr, section #2 Ringwood Station,base of section
2RMTR
-24.10169
134.80276
335
Ringwood Mbr,Todd River Station, base of section
EC
-23.78641
133.07576
666
Areyonga Fm, Ellery Creek, base of section
3EC
-23.78896
133.07452
665
Ringwood Mbr(?),Ellery Creek
SB
-24.20541
134.64101
386
Areyonga-Ringwood-Olympic(?), Star Bore, Todd River Station, base of section
1ED
-24.05511
134.61856
388
Olympic Fm, Mt. Capitor, base of section
2ED
-24.04875
134.60796
461
Olympic Fm #2, Mt. Capitor, base of section
TRL
-24.03486
134.63686
338
Limbla Mbr, Todd River Station, base of section
8.2 XRD plots
52
53
54
55
56
8.3 Data tables Sample name IOT0
δ13C
Stratigraphic height (m)
δ18O
Yield
0
-1.481
-4.108
1.3
IOT0-1
0.1
-1.011
-4.172
1.2
IOT0-2
0.2
-0.279
-3.564
5.7
IOT0-3
0.3
-1.450
-4.475
2.2
IOT0-4
0.4
-1.190
-4.304
2.6
1
-0.794
-2.510
0.8
IOT1-1
1.1
-1.447
-4.118
4.1
IOT1-2
1.2
-1.199
-3.794
1.5
IOT1-3
1.3
-0.875
-4.308
2.1
IOT1-4
1.4
-1.666
-4.079
0.8
IOT1-6
1.6
-1.678
-3.797
1.0
IOT1-9
1.9
-1.344
-4.024
1.1
IOT2-0
2
-1.338
-3.979
1.0
IOT2-1
2.1
-0.988
-2.710
0.8
IOT2-2
2.2
-1.163
-3.518
3.2
IOT2-3
2.3
-1.084
-3.823
1.1
IOT2-4
2.4
-1.009
-3.452
2.2
IOT13
13
-2.379
-6.994
0.8
IOT13-1
13.1
-3.669
-7.585
2.0
IOT13-2
13.2
-2.047
-5.485
2.2
IOT13-3
13.3
-2.920
-6.233
1.1
IOT13-4
13.4
-3.987
-7.074
1.0
IOT13-48
13.48
-3.480
-6.966
0.9
IOT13-55
13.55
-3.509
-8.500
1.5
1ED3-35
3.35
1.135
-3.854
4.8
1ED3-5
3.5
1.088
-3.573
2.4
1ED3-8
3.8
0.084
-4.118
1.5
1ED5-3
5.3
0.719
-3.736
1.7
1ED5-5
5.5
0.926
-4.170
2.7
1ED5-6
5.6
0.647
-4.957
1.5
1ED5-8
5.8
0.849
-4.714
2.1
1ED6-5
6.5
0.827
-4.697
1.5
1ED7-6
7.6
0.972
-4.426
1.6
1ED8-6
8.6
0.654
-4.729
3.9
1ED9-6
9.6
-1.749
-5.649
2.4
1ED10-6
10.6
-1.446
-5.397
3.0
1ED11-4
11.4
-1.758
-5.854
6.6
1ED12
12
-1.763
-6.218
0.5
1ED13-0
13
-1.812
-5.850
4.6
1ED14
14
-1.993
-5.931
2.3
1ED15-0
15
-1.355
-5.681
3.5
IOT1
57
1ED16
16
-2.105
-5.737
2.0
1ED17-0
17
-2.003
-5.819
3.3
1ED18
18
-2.212
-6.193
1.8
1ED19-0
19
-2.194
-6.233
3.0
1ED20
20
-2.187
-6.335
1.0
1ED21-0
21
-2.273
-6.125
1.5
1ED22
22
-2.260
-6.276
1.8
1ED23-0
23
-2.445
-5.909
5.1
1ED24
24
-2.358
-6.203
7.0
1ED25-0
25
-2.549
-6.099
3.6
1ED26
26
-2.348
-5.992
2.7
1ED27-0
27
-2.729
-5.793
4.3
1ED28
28
-3.018
-6.199
2.9
1ED30-3
30.3
-3.242
-5.346
10.0
1ED31-0
31
-3.423
-5.152
2.8
1ED32
32
-3.489
-5.689
2.8
1ED33-0
33
-3.726
-5.780
8.1
1ED34
34
-3.795
-5.969
4.0
1ED34
34
-3.894
-6.073
1.0
1ED34-2
34.2
-3.818
-6.619
3.0
1ED34-5
34.5
-4.117
-6.482
5.4
1ED34-5
34.5
-4.163
-6.695
4.3
1ED37-0
37
-4.289
-6.336
5.7
1ED37-5
37.5
-6.531
-14.608
2.6
1ED37-5
37.5
-5.981
-13.567
2.7
1ED37-7
37.7
-6.040
-12.374
8.9
1ED38-0
38
-5.975
-11.628
9.2
1ED38-2
38.2
-6.158
-11.984
6.2
1ED38-3
38.3
-6.304
-13.068
6.3
2ED6-6
6.6
-0.521
-4.208
4.7
2ED6-8
6.8
-0.809
-4.391
3.0
2ED7-0
7
-1.026
-4.969
0.4
2ED7-2
7.2
0.572
-5.203
1.1
2ED8-2
8.2
1.124
-3.758
1.5
2ED8-7
8.7
-1.135
-5.096
2.7
2ED9-2
9.2
-1.175
-5.428
0.6
2ED10
10
-0.974
-5.033
0.9
2ED11
11
-1.143
-5.282
1.7
2ED12
12
-1.189
-5.522
1.6
2ED13
13
-1.733
-5.819
0.2
2ED14
14
-1.322
-5.336
3.7
2ED15
15
-1.714
-5.883
1.0
2ED15-9
15.9
-1.722
-5.440
0.9
2ED16-9
16.9
-1.760
-5.825
4.2
58
2ED18
18
-1.936
-5.942
6.3
2ED18-6
18.6
-2.032
-6.372
0.6
2ED19-7
19.7
-2.011
-5.613
3.9
2ED20-9
20.9
-1.915
-5.981
3.0
22
-2.219
-6.167
2.2
22.6
-2.325
-5.948
0.3
24
-2.920
-7.931
-0.2
2ED25-3
25.3
-2.376
-6.138
0.5
2ED26-1
26.1
-2.194
-6.225
2.3
2ED28-5
28.5
-2.385
-6.050
0.2
2ED29-5
29.5
-2.590
-5.946
0.8
2ED30-5
30.5
-2.472
-5.779
0.5
41
-3.648
-6.014
0.6
42.1
-3.950
-6.295
0.5
44
-4.465
-7.726
0.3
2ED46-7
46.7
-4.161
-5.927
0.0
2ED47-5
47.5
-4.024
-5.560
6.2
2ED47-7
47.7
-4.286
-6.010
5.6
2ED49-6
49.6
-4.298
-5.795
6.2
2ED50-7
50.7
-6.547
-12.064
4.1
2ED50-9
50.9
-3.067
-7.100
6.3
51
-5.746
-9.637
1.9
51.3
-4.706
-10.730
2.5
0
6.688
-0.296
14.7
IRR0-06
0.06
6.229
0.001
12.0
IRR0-12
0.12
5.948
-0.067
4.7
IRR0-18
0.18
5.913
-0.300
10.2
IRR0-24
0.24
5.587
-0.453
10.5
IRR0-3
0.3
5.018
-1.158
5.9
TRL5-1
5.1
9.172
-9.414
1.2
6
8.191
-7.411
1.4
TRL8
8
8.320
-7.351
0.9
TRL10
10
8.146
-9.139
1.1
TRL11
11
8.123
-7.824
0.7
14.2
9.798
-9.900
4.8
TRL17
17
7.326
-8.437
1.7
TRL28
28
8.086
0.463
2.7
TRL28
28
7.950
0.657
4.2
TRL29
29
6.032
-8.613
3.4
2ED22 2ED22-6 2ED24
2ED41 2ED42-1 2ED44
2ED51 2ED51-3 IRR0
TRL6
TRL14-2
TRL30
30
8.429
-9.332
1.4
34.5
7.672
-6.844
3.2
TRL35
35
9.000
-8.828
3.6
TRL48
48
5.862
-3.270
0.5
48.5
7.248
-6.527
0.6
TRL34-5
TRL48-5
59
TRL49
49
8.779
-8.260
4.8
49.5
6.704
-12.046
4.9
TRL50
50
8.257
-8.452
3.1
TRL51
51
7.635
-8.116
1.9
TRL51-6
51.6
6.816
-5.310
1.3
TRL53-4
53.4
1.411
-4.424
3.8
TRL53-4
53.4
1.435
-4.505
13.8
TRL54-6
54.6
7.521
-9.264
1.1
TRL57-6
57.6
6.512
-7.600
1.0
TRL57-8
57.8
6.846
-8.263
1.2
TRL67-6
67.6
5.162
-5.073
0.7
TRL80-1
80.1
4.946
-4.905
1.0
81
6.297
-2.347
3.9
81.5
6.348
-4.174
5.9
TRL83
83
5.246
-4.506
1.8
TRL84
84
5.222
-2.171
3.9
ILM0
0
7.335
-9.870
15.3
ILM1
1
7.278
-8.992
0.8
ILM1-5
1.5
7.504
-8.698
9.5
ILM2-5
2.5
7.756
-8.538
1.4
TRL49-5
TRL81 TRL81-5
ILM3
3
8.770
-8.235
8.5
3.5
8.940
-8.963
4.6
6
9.964
-6.958
8.5
ILM6-3
6.3
9.543
-7.977
10.5
ILM6-6
6.6
9.722
-8.617
12.1
7
9.784
-6.315
6.4
ILM7-5
7.5
9.660
-6.454
13.1
ILM8-5
8.5
10.140
-6.825
13.9
ILM10
10
8.752
-6.415
28.6
ILM12
12
9.093
-5.577
12.5
ILM13-5
13.5
8.737
-6.089
19.7
ILM14-5
14.5
9.436
-8.789
6.2
ILM18-5
18.5
9.289
-7.244
7.4
20
8.424
-8.846
-0.2
20.7
7.816
-7.345
1.7
30
8.439
-7.597
6.5
43.5
4.459
-4.937
6.8
0
3.028
-5.132
2.2
0.6
2.817
-5.259
1.0
IRMT2
2
3.006
-5.329
0.6
IRMT9
9
2.637
-6.532
1.0
IRMT10
10
2.376
-7.450
0.8
IRMT25
25
1.923
-4.865
3.3
IRMT26
26
2.152
-5.196
0.5
ILM3-5 ILM6
ILM7
ILM20 ILM20-7 ILM30 ILM43-5 IRMT0 IRMT0-6
60
IRMT36
36
2.741
-7.617
0.0
IRMT38
38
2.644
-6.831
1.1
IRMT41
41
3.205
-4.365
-0.1
IRMT54
54
3.311
-3.520
0.7
IRMT57-5
57.5
4.062
-2.604
1.0
IRMT58-5
58.5
3.965
-3.388
4.2
IRMT70-5
70.5
2.586
-4.836
0.7
IRMT71-2
71.2
2.889
-3.276
0.3
IRMT71-7
71.7
3.317
-3.359
0.6
72
3.259
-2.883
2.7
79.3
3.328
-3.761
1.9
81
3.155
-3.081
1.1
86.5
3.356
-2.993
0.4
IRMT95
95
0.964
-2.993
1.7
IRMT113
113
1.673
-7.163
1.5
IRMT120
120
3.339
-2.003
1.2
IRMT190
190
2.500
-2.149
0.6
IRMT190-15
190.15
2.571
-2.634
3.6
IRMT190-3
190.3
2.519
-2.565
1.6
IRMT190-38
190.38
2.184
-2.390
0.2
IRMT72 IRMT79-3 IRMT81 IRMT86-5
IRI1
1
0.540
-0.988
0.6
IRI8-5
8.5
2.146
-0.718
0.6
IRI26-5
26.5
0.772
-0.606
0.6
IRI27
27
1.356
-1.446
0.9
IRI34
34
0.076
-3.699
0.9
IRI37
37
0.271
-3.659
-0.2
IRI58
58
1.684
-2.801
-0.1
IRI91
91
0.371
-2.642
0.6
IRI99
99
1.963
-3.906
0.6
IRI105
105
2.612
-3.833
1.6
IRI107
107
2.724
-5.572
3.6
IRI223
223
1.751
-8.495
0.5
IRI223-5
223.5
1.427
-11.357
0.4
IRI224-5
224.5
0.897
-8.343
0.1
242
2.035
-11.475
2.3
244.5
3.343
-12.693
2.2
IRI242 IRI244-5 IRI246
246
1.941
-11.031
2.3
247.2
2.809
-12.198
0.8
IRI252
252
1.167
-7.860
1.2
IRI253
253
2.202
-6.984
3.3
IRI255
255
1.862
-6.767
2.4
IRI257
257
4.254
-5.137
2.5
IRI259
259
2.890
-5.453
0.9
0
-4.672
-7.718
0.6
IRI247-2
2RMTR0
61
2RMTR0-2
0.2
-3.755
-6.041
0.9
2RMTR44
44
-1.397
-5.650
2.5
2RMTR48
48
-1.077
-5.370
1.8
2RMTR70
70
-0.438
-5.657
0.7
2RMTR80
80
-1.820
-5.784
2.6
2RMTR81
81
-2.573
-5.035
5.2
2RMTR82
82
-3.070
-4.907
6.2
2RMTR89
89
-0.366
-6.207
2.5
2RMTR93
93
0.267
-5.082
2.9
2RMTR134-4
134.4
0.407
-2.699
1.2
2RMTR160-9
160.9
-1.102
-4.319
0.6
2RMTR171-2
171.2
-0.243
-2.170
4.2
2RMTR173-9
173.9
0.367
-0.834
4.6
2RMTR188-6
188.6
-1.442
-4.525
0.9
2RMTR191-4
191.4
0.230
-1.826
2.4
2RMTR195-1
195.1
-0.428
-4.565
1.4
2RMTR196-4
196.4
-1.004
-3.475
2.8
2RMTR196-9
196.9
-0.254
-3.178
7.1
2RMTR200-3
200.3
0.355
-2.165
4.6
2RMTR201-1
201.1
0.196
-4.329
6.6
2RMTR206-9
206.9
-0.035
-2.588
6.0
2RMTR207-9
207.9
-0.564
-4.381
6.7
2RMTR212--9
212.9
-2.365
-4.786
0.9
2RMTR218-9
218.9
-0.529
-4.870
2.3
2RMTR222-4
222.4
-1.124
-1.862
1.3
2RMTR229-4
229.4
-1.225
-2.937
0.9
SB0-0
0
-3.569
-6.824
2.6
SB0-5
0.5
-0.920
-4.777
3.4
SB1
1
-0.160
-4.410
17.0
SB1-5
1.5
-0.724
-4.343
5.2
SB3-5
3.5
-0.298
-4.948
5.6
SB5-5
5.5
-0.580
-4.489
1.0
SB10-5
10.5
-0.071
-2.947
3.5
SB16
16
-0.624
-6.975
3.3
SB19
19
-0.660
-6.254
3.2
SB22
22
1.273
-3.551
11.2
SB32-5
32.5
-0.295
-5.434
13.4
SB34
34
-2.095
-13.205
2.2
SB35
35
0.036
-2.539
5.5
SB40
40
-2.515
-6.269
4.4
SB43-5
43.5
-1.513
-3.809
5.2
SB44-5
44.5
-0.518
-6.849
6.4
SB45
45
-1.136
-6.523
2.3
SB46
46
-0.810
-5.391
4.6
62
SB49
49
-2.363
-2.799
3.0
SB50-2
50.2
-1.085
-3.997
6.4
SB50-5
50.5
-4.238
-4.817
1.9
SB51-5
51.5
-1.745
-3.689
5.6
52
-1.760
-4.068
4.6
SB53-5
53.5
-2.785
-5.176
0.9
SB498
498
3.022
-5.184
4.0
SB499
499
3.315
-3.151
6.2
SB500
500
3.305
-5.490
1.6
SB501
501
3.120
-5.436
1.7
SB512
512
3.569
-10.955
3.5
SB519
519
3.137
-10.518
3.9
523.5
3.739
-5.971
7.1
SB527
527
3.971
-4.957
7.7
SB529
529
3.478
-3.481
2.0
SB988
988
2.027
-4.438
3.1
SB989
989
3.977
-3.012
13.4
SB990
990
3.250
-2.977
15.3
SB994
994
3.906
-4.553
5.4
SB995
995
1.566
-5.858
6.2
SB1024
1024
-1.712
-4.428
8.7
SB1025-1
1025.1
-3.514
-5.790
5.2
SB1025-2
1025.2
-2.536
-4.318
5.1
SB1025-4
1025.4
-2.796
-5.363
8.4
SB1025-5
1025.5
1.173
-8.229
14.5
SB1025-5
1025.5
0.803
-8.278
1.0
SB1025-6
1025.6
-3.165
-5.967
3.3
SB1025-8
1025.8
-2.970
-6.402
22.8
SB1025-9
1025.9
-3.350
-5.696
3.7
SB1026-2
1026.2
-2.898
-5.536
13.7
SB1026-4
1026.4
-4.323
-7.231
1.1
SB1026-6
1026.6
-3.279
-5.365
7.6
SB1026-7
1026.7
-4.637
-8.292
3.6
1027
-2.451
-5.365
6.2
SB1027-6
1027.6
-3.151
-5.446
18.7
SB1027-7
1027.7
-3.805
-5.412
11.2
SB1033-5
1033.5
-2.579
-5.106
2.8
SB1036-7
1036.7
-3.301
-4.907
12.8
1037
-3.254
-4.815
5.2
SB1037-2
1037.2
-3.652
-6.121
2.7
SB1037-5
1037.5
-3.536
-5.833
6.7
SB1037-8
1037.8
-3.950
-5.642
11.9
1038
-3.409
-5.158
8.3
0
2.505
-2.502
4.7
SB52
SB523-5
SB1027
SB1037
SB1038 3EC0
63
3EC0
0
2.469
-2.605
5.1
3EC1
1
1.489
-2.223
4.8
3EC2
2
1.981
-1.858
1.4
3.5
0.603
-2.021
7.2
3EC6
6
1.533
-2.251
8.8
3EC7
7
0.979
-5.244
3.6
EC0
0
3.208
-5.534
7.2
0.75
3.307
-4.569
6.7
2
1.572
-5.227
15.2
2.5
1.875
-5.340
10.0
EC103-5
103.5
-1.836
-10.560
13.9
EC103-7
103.7
-2.148
-10.011
4.7
3EC3-5
EC0-75 EC2 EC2-5
EC107
107
2.520
-1.365
9.1
EC109-4
109.4
-1.100
4.692
9.2
EC109-8
109.8
-0.703
3.241
15.1
EC116
116
2.095
-4.265
4.3
EC141
141
2.441
-2.473
9.9
64
