Malcolm Wallace

University of Melbourne | MSD · School of Earth Sciences

The greenhouse-to-icehouse climate transition from the Eocene into the Oligocene is well documented by sea surface temperature records from the southwest Pacific and Antarctic margin, which show evidence of pronounced long-term cooling. However, identification of a driving mechanism depends on a better understanding of whether this cooling was also...

The evolution of the global carbon and silicon cycles is thought to have contributed to the long-term stability of Earth’s climate1–3. Many questions remain, however, regarding the feedback mechanisms at play, and there are limited quantitative constraints on the sources and sinks of these elements in Earth’s surface environments4–12. Here we argue...

Molecular phylogenetic data suggest that photosynthetic eukaryotes first evolved in freshwater environments in the early Proterozoic and diversified into marine environments by the Tonian Period, but early algal evolution is poorly reflected in the fossil record. Here, we report newly discovered, millimeter- to centimeter-scale macrofossils from ou...

The Gippsland Basin contains some of the largest hydrocarbon accumulations in Australia, and has been in production since the 1920's. These hydrocarbons are trapped by large growth anticlines offshore, in reservoirs of the Cretaceous to Eocene-aged Latrobe Group. Despite the obvious importance of these growth anticlines, the timing of their formati...

Floral Lagerstätten deposits (i.e., fossil sites with exceptional preservation and diversity) are preserved within the Miocene brown coals of the Latrobe Group, Gippsland Basin, Australia. Three independent mechanisms are conducive to their accumulation. Throughout the coal seams the conversion of plant material into charcoal (fusain) and its accum...

The Great Barrier Reef of Australia is the largest modern coral reef system on Earth. However, a similar-sized barrier reef (~2000 km long) existed on Australia’s north-western margin in the middle Miocene and to some extent, still exists today. Seismic profiles reveal that this reef system was first initiated in the late Paleogene (~34-28 Ma) and...

The Earth’s most severe ice ages interrupted a crucial interval in eukaryotic evolution with widespread ice coverage during the Cryogenian Period (720 to 635 Ma). Aerobic eukaryotes must have survived the “Snowball Earth” glaciations, requiring the persistence of oxygenated marine habitats, yet evidence for these environments is lacking. We examine...

The concurrent development of a cool‐carbonate Miocene clinoform system and the tropical reef which developed on its shelf in the North Carnarvon Basin is studied. The study, based on seismic interpretation and geometrical analysis, seeks to investigate how the architecture of the clinoforms develops in relation to the advance of the reef‐margin, p...

Neoproterozoic cap dolomites are unusual and distinctive marker units that occur after large Cryogenian glaciations. Several thin dolomite units that have features resembling cap dolomites occur within the Cryogenian-Ediacaran succession of the Adelaide Geosyncline. While each of these dolomite units has distinctive features, they also share many s...

A new mid-latitude terrestrial climate proxy record is presented for southeastern Australia. The Middle Eocene to Middle Miocene palynofloral and δ¹³C record of the Latrobe Group, Gippsland Basin, details that the climate of southeastern Australia, paleolatitude 60–50°S, supported the growth of highly diverse subtropical to cool-temperate rainfores...

New palynological analysis of the Middle Eocene to Middle Miocene Latrobe Group coals of the Gippsland Basin in Australia sheds new light on fire adaptation in Australia’s modern flora. The distribution of charcoal and fire-prone flora within brown coals is entirely controlled by facies and the paleoenvironments within the peatland, and does not re...

The Cenozoic spore-pollen zonation scheme of southeastern Australia is used to constrain the ages of marine and terrestrial strata throughout Australasia. New palynological, strontium isotope and foraminiferal data from the Torquay and Gippsland basins in southeastern Australia are here used to revise and chronologically calibrate the Oligocene and...

The Kingston Peak Formation records glacial sedimentation during the Cryogenian in Death Valley, California, and contains iron formation horizons. These iron formations are part of a thick sedimentary succession containing glaciogenic diamictites, together with mass flow breccias, conglomerates, sandstones and siltstones. The Kingston Peak iron for...

Metal and metal isotope records in carbonates have the potential to provide novel insights into ancient ocean–atmosphere redox conditions, paleoenvironmental conditions, and biogeochemical cycling. However, trace element geochemical signatures in carbonates can record either diagenetic or depositional signatures. Here we explore the variability in...

The Chuos Formation of Namibia is the sedimentary product of the Neoproterozoic Sturtian (c. 720–660 Ma) glaciation and contains massive diamictites intercalated with finely laminated iron formation. Similar Sturtian glacially associated iron formations are found globally. The iron formations are laminated and generally very pure. The diamictites a...

The reason for the abundance of dolomite lithologies in Earth's early geological record compared to modern environments remains contentious. This study provides new insight into this Precambrian “dolomite problem” by revisiting one of the most controversial dolomite localities, the Beck Spring Dolomite, of Death Valley, USA. Consistent with some pr...

Zebra textures are enigmatic banded fabrics that occur in many carbonate-hosted ore deposits, dolomite hydrocarbon reservoirs and carbonate successions globally. They consist of a variety of minerals and are characterised by parallel light and dark bands that occur at a millimetre- to centimetre-scale. Based on petrological evidence, there is gener...

The primary mineralogy of marine carbonate precipitates has been a crucial factor in constraining the major element composition of ancient oceans. Secular changes in Phanerozoic marine chemistry, including Mg/Ca, have been well-documented using the original carbonate mineralogy of ooids, marine cements and biominerals. However, the history of Preca...

Peats are commonly used in paleoenvironmental and paleoclimatic studies but detailed sedimento-logical and facies models for peatlands are poorly developed relative to other sedimentary settings. A comparison of the palynology and charcoal abundances in modern and ancient Cenozoic peats (i.e., brown coals) demonstrates that, in a single cycle, thei...

There has been extensive debate about the history of Earth's oxygenation and the role that land plant evolution played in shaping Earth's ocean–atmosphere system. Here we use the rare earth element patterns in marine carbonates to monitor the structure of the marine redox landscape through the rise and diversification of animals and early land plan...

A detailed examination of the brown coal facies preserved in the Latrobe Valley Morwell 1B seam indicates that the type of peat-forming environment and the associated hydrological regime are the main factors influencing the development of lithotypes in brown coal deposits. New palynological data from the Morwell 1B seam suggests that each respectiv...

Emerging geochemical proxies have improved our understanding of the broad-scale history of Earth's oxygenation. However, paleoredox work does not always include extensive consideration of sample preservation and paleoenvironmental setting. This is particularly an issue with marine carbonates, which although being potentially ideal ocean redox archi...

The cyclic succession of brown coals in the Latrobe Valley, Gippsland Basin, Australia, records an exceptional floral and charcoal record from the Late Oligocene to Middle Miocene. New palynological, geological and charcoal data are consistent with existing colourimetry, carbon isotope, and organic geochemical and palaeobotanical data, indicating t...

The Neoproterozoic Sturtian glaciation is considered to be among the most severe glaciations in Earth history, possibly encompassing the entire planet and lasting for more than 50 m.y. Iron formations are globally associated with Sturtian glacial successions, although the influence of glaciation on the genesis of these iron formations remains conte...

Brown coal colour lithotype cycles range from 10 to 30 m thick in Oligo-Miocene coals of the Latrobe Valley, Gippsland Basin, Australia. Similar colour lithotype cycles occur in the and Lusatia German Miocene brown coals. In both the Latrobe Valley and Germany, the cycles often display well-developed colour-lightening-upward trends as defined by ne...

The late Cenozoic carbonates of the Northwest Shelf are important subsidence history archives that also cause significant sonic velocity problems affecting seismic imaging of underlying strata. Despite their substantial thickness and areal extent, these carbonates have been sampled only in engineering foundation boreholes and as cuttings and rare s...

The Early Carboniferous stratigraphy of the Irish Midlands contains one of the world?s major carbonate-hosted zinc-lead orefields covering a region of approximately 8000 km2. The large-scale nature of the sedimentary fluid flow systems that produce these ore deposits suggest it is necessary to understand not only the nature of mineralisation, but a...

Recently acquired seismic reflection data, combined with detailed subsurface stratigraphic analysis (core analysis and gamma ray logs) reveal a new view of Lower Carboniferous stratigraphy and tectonism in Ireland. Seismic stratigraphic relationships and stratal thickness variations within Tournaisian units indicates that the Ballinalack High (and...

The Holowilena Ironstone is a Neoproterozoic iron formation in South Australia associated with glacial deposits of the Sturtian glaciation. Through a comprehensive field study coupled with optical and scanning electron microscopy, X-ray fluorescence, and X-ray diffraction, a detailed description of the stratigraphy, sedimentology, mineralogy, and s...

In 2010–2011, a well on the uplifted northern edge of the Latrobe Valley (Yallourn North-1A) cored a 550 m section of mostly arenaceous sediments from the Lower Cretaceous Tyers River Subgroup. A follow-up core-hole (Yallourn Power-1) aimed at extending the Tyers River Subgroup section some 5 km south into the Latrobe Valley instead encountered Pal...

The Neoproterozoic was a time of great change in the Earth's surface and marine environments, including extensive climate variability, the widespread oxygenation of the oceans and the accompanying rise of animal life. However, the timing of ocean oxygenation remains uncertain, particularly in regard to Cryogenian seas, which were disrupted by large...

The Ombombo Subgroup of the Otavi Fold Belt, Kaokoveld, Namibia preserves a succession of clastic and carbonate sediments with unusual sedimentary features. The stratigraphy of these units is discussed here in detail for the first time since their initial definition, with particular emphasis carbonate sedimentology. Early Neoproterozoic shales of t...

A wide range of maturation parameters indicates that near-surface Devonian sequences of the eastern Lennard Shelf are immature (peak temperatures of 70–90°C). Fluid inclusion microthermometry indicates that peak temperatures in the Palaeozoic were probably around 60 to 70°C for presently exposed or near-surface rocks. Mississippi Valley-type (MVT)...

The Cryogenian Balcanoona reef complexes of South Australia consist of several dolomite platforms with well-defined backreef, reef margin and slope/basinal facies. The mature platforms have prograded large distances into the basin (N 15 km) and have high relief margins (over 1 km of relief at the platform margin). Backreef facies are dominantly ooi...

Neoproterozoic oceans provided the setting for the rise of animals, yet little is known of their chemical composition. Marine carbonates from the Cryogenian Oodnaminta Reef Complex, South Australia, reveal the chemical structure of a Neoproterozoic ocean. Pseudo-depth profiles from shallow- to deep-water reef facies have been constructed from geoch...

McLaren, S.N., Wallace, M.W., Gallagher, S.J. and Wagstaff, B.E., Tosolini, A-M, P. 2014, Chapter 12, The development of a climate – an arid continent with wet fringes, in, Prins, H. & Gordon, I. eds., Invasion Biology and Ecosystem Theory (Cambridge University Press), 256-280 ISBN: 9781107035812

Fossil, facies, and isotope analyses of an early high‐paleolatitude (55°S) section suggests a highly unstable East Antarctic Ice Sheet from 32 to 27 Myr. The waxing and waning of this ice sheet from 140% to 40% of its present volume caused sea level changes of +25 m (ranging from ‐30 to +50 m) related to periodic glacial (100,000 to 200,000 years)...

Fossil, facies, and isotope analyses of an early high-paleolatitude (55°S) section suggests a highly unstable East Antarctic Ice Sheet from 32 to 27 Myr. The waxing and waning of this ice sheet from 140% to 40% of its present volume caused sea level changes of ±25 m (ranging from -30 to +50 m) related to periodic glacial (100,000 to 200,000 years)...

The Lower Devonian Rocky Camp Member of the Murrindal Limestone, Buchan Group of southeastern Australia consists of a series of carbonate mud-mounds and smaller lagoonal bioherms. The Rocky Camp mound is the best exposed of the mud-mounds and has many characteristics in common with Waulsortian (Carboniferous) mounds. Detailed paleoecological and se...

Stratigraphic and sedimentological investigation of the interglacial succession within the Cryogenian-aged Umberatana Group of the Northern and Central Flinders Ranges reveals a complex array of sedimentary successions lying between the Sturtian and Marinoan glacial deposits. The Sturtian–Marinoan Series boundary was first defined from the Adelaide...

Analysis of the synsedimentary diagenetic phases from a pervasively dolomitised Cryogenian (~ 650 Ma) reef complex, South Australia reveals a fundamentally different style of marine diagenesis to that of Phanerozoic carbonates. Textural evidence from dolomitised and undolomitised lithologies of the Oodnaminta Reef Complex indicates that depositiona...

The ephemeral lacustrine carbonates of the Bungunnia Limestone, deposited in palaeo megalake Bungunnia, preserve a detailed record of Pleistocene palaeoenvironmental and palaeoclimatic change in southeastern Australia. Five distinct lake shorelines (Lake Levels 0–4) are visible on digital elevation models, ranging in elevation from around 70 m to 3...

The Australian continent is large and therefore exhibits a range of very different climatic zones. Broadly, the continent is characterised by arid climatic regimes: four-fifths of the landmass receiving an annual rainfall of less than 600mm (Figure 12.1) and one-half of the continent receiving less than 300mm. These arid and semi-arid regions form...

Halogen ratios (Br/Cl and I/Cl) and concentrations provide important information about how sedimentary formation waters acquire their salinity, but the possible influence of organic Br derived from sedimentary wall-rocks is rarely quantified. Here, it is demonstrated that Br/Cl versus I/Cl mixing diagrams can be used to deconvolve organic Br contri...

The extraordinary abundance of dolomite in the Proterozoic challenges our understanding of Precambrian marine environments. Here we show that synsedimentary marine dolomite precipitation was pervasive within Cryogenian reef complexes from the Adelaide Fold Belt, South Australia. Although these reefs are composed of dolomite, textural evidence indic...

The Cryogenian succession of the Northern Flinders Ranges reveals a complex sedimentary record between the Sturtian and Marinoan glacial deposits. A major unconformity separates the Sturtian and Marinoan-aged sedimentary successions in the area. This forms a subaerial erosion surface with terrestrial and marginal marine infill directly above the An...

The Murray Basin is a low-lying but extensive intracratonic depocentre in southeastern Australia, preserving an extraordinary record of Late Neogene sedimentation. New stratigraphic and sedimentologic data allow the long-term evolution of the basin to be re-evaluated and suggest a significant role for: (1) tectonism in controlling basin evolution,...

Profiles of five Paleogene rivers reconstructed from basalts that flowed down them show a complex landscape. All five flow fields are in Victoria's Eastern Uplands, two in the Baw Baw region in the southwest and three in the Nunniong–Deddick region in the east. Three flow fields (Toorojil, Aberthomson, Timbuchan) originate on high plateaus (

Extreme global climate change in the Late Neogene is well known. In Australia, climate changed from wet conditions in the Late Neogene to the arid conditions that characterize much of the continent today. We constrain the nature and timing of the onset of aridity in southeastern Australia by detailed stratigraphic analysis of palaeo megalake Bungun...

An examination of the deeply incised Ediacaran Wonoka canyons in the Adelaide Geosyncline (most recently interpreted as subaerial valleys) demonstrates their submarine origin, and confirms them as some of the best examples of ancient outcropping submarine canyons in the world. The entire canyon-fill succession is interpreted to be of deep-water (be...

A detailed sedimentological and chronostratigraphic analysis of the Umberatana Group in the northern Adelaide Geosyncline has uncovered a depositional history involving the rapid progradation (at least 20 km) of a giant reef complex (up to 1.1 km relief) during mid-Cryogenian interglacial times. The reef complex, which occurs in the Balcanoona Form...

Sediments of the Loxton–Parilla Sands form a progradational strandplain that stretches for over 350 km across the Murray Basin, in southeastern Australia. The strandplain comprises over 600 individual ridges, with stratigraphic and strontium isotope data indicating these strandlines are Late Miocene to Early Pliocene in age, with deposition beginni...

The Otway, Gippsland and central coast basins (including the Torquay Basin, Sorrento Graben and Port Phillip Basin) preserve one of the most complete records of Mesozoic and Cenozoic sedimentation in southern Australia. However, robust age constraints on sedimentation are scarce. Strontium isotope analysis of calcitic bioclasts from the Jan Juc Mar...

A combined sedimentary and isotopic analysis of the Sturtian-aged Tindelpina cap carbonate in South Australia has revealed a strong relationship between sedimentary facies and δ13Ccarb. Depositional water depths for the cap carbonate are difficult to constrain, however, a lack of diagnostic shallow water structures and the inferred magnitude of pos...

Paleo Lake Bungunnia covered more than 40 000 km 2 of southern Australia during the Plio-Pleistocene, although the age and origin of the lake remain controversial. The Blanchetown Clay is the main depositional unit and outcrop at Nampoo Station in far-western New South Wales provides the most continuous lacustrine section preserved in the basin. He...

Foraminiferal analysis of Miocene to recent strata of the Northwest Shelf of Australia is used to chart West Pacific Warm Pool (WPWP) influence. The assemblage is typified by ``larger'' foraminifera with ingressions of the Indo-Pacific ``smaller'' taxa Asterorotalia and Pseudorotalia at around 4 Ma and from 1.6 to 0.8 Ma. A review of recent and fos...

The carbon-isotope and palynological record through 580 m thick almost continuous brown coal in southeast Australia's Gippsland Basin is a relatively comprehensive southern hemisphere Middle Eocene to Middle Miocene record for terrestrial change. The carbon isotope δ¹³Ccoal values of these coals range from − 27.7‰ to − 23.2. This isotopic variabili...

Analysis of a Cryogenian interglacial platform margin in the Adelaide Geosyncline reveals a strong carbonate δ13C-facies relationship. Detailed chronostratigraphic correlation between sections ranging from shallow platform facies to deep basinal facies indicates the presence of a carbon isotopic gradient of between 8 and 11‰ in time-equivalent stra...

Foraminiferal analysis of Miocene to recent strata of the Northwest Shelf of Australia is used to chart West Pacific Warm Pool (WPWP) influence. The assemblage is typified by "larger" foraminifera with ingressions of the Indo-Pacific "smaller" taxa Asterorotalia and Pseudorotalia at around 4 Ma and from 1.6 to 0.8 Ma. A review of recent and fossil...

Phosphates are present on the surface of the Mio-Pliocene unconformity in the Otway, Port Phillip and Gippsland basins of south-east Australia. The phosphates occur as lenticular lag deposits and include reworked phosphatic intraclasts, vertebrate bone and teeth. In situ phosphatized burrows are also found in sediments of Late Miocene and Early Pli...

Strontium isotope data indicate that sediments of the Norwest Bend Formation were deposited within a large estuarine system during the Latest Miocene to Early Pliocene (probably > 5 Ma). The Norwest Bend Formation is divisible into two members; a lower sand-dominated member and an upper oyster coquina member. These two units are separated by an irr...

Since the idea of the Pliocene Kosciusko Uplift in the Southeastern Highlands of Australia was first introduced, there has been considerable debate about the validity of this Cenozoic uplift event. Until the mid 1990s, most researchers argued that most highland relief was present by the Cretaceous. Since the late 1990s, there has been a paradigm sh...

A palynological study of oil exploration wells in the Gippsland Basin southeastern Australia has provided a record of southern high latitude climate variability for the last 12 million years of the Cretaceous greenhouse world. During this time, the vegetation was dominated by a cool to temperate flora of Podocarpaceae, Proteaceae and Nothofagidites...

The 100-m thick Middle Miocene Yallourn brown coal seam was the last of the major Latrobe Valley Group seams to form in the Gippsland Basin (southeastern Australia) and the final major coal to form in Australia. Coal deposition coincided with the Middle Miocene climatic optimum. During this warm period of relatively high sea-levels, high water tabl...

The modern Bass Canyon is one of the world's largest submarine canyon systems that is entirely located within a cool-water carbonate environment. Five large shelf-breaching and three slope-confined tributary canyons coalesce on the lower slope and enter the massive deep-water Bass Canyon at 3000 m depth. Normal slope sediments consist predominantly...

The Gippsland Basin on Australia's southeastern continental margin is host to a number of large shelf-breaching canyons that form part of the Bass Canyon system. Analysis of high-resolution bathymetry data and biostratigraphically controlled shallow seismic data across the shelf and upper slope and associated canyon heads shows that widespread eros...

A thick, areally extensive subsurface sequence of Upper Devonian carbonates occurs on the Barbwire Terrace in the Canning Basin of Western Australia. It is a platform sequence in which most of the shallow water lithologies have been thoroughly dolomitized. Slightly deeper water marls have remained as limestones. The major, regional dolomite type is...

Basaltic eruptions across the Central Highlands of Victoria have sealed in-place Early to middle Cenozoic palaeodrainage systems (also known as deep leads). The basal gravels of the deep leads have been mined extensively in the past for their rich placer-gold deposits. Detailed mapping of the distribution of all palaeorivers has been carried out us...

The warm greenhouse world of the Late Cretaceous created oceans that were poorly stratified latitudinally and vertically. Periodically these oceans experienced globally significant events where oxygen minimum zones enveloped the continental margins. Evidence of the effect of one of these Ocean Anoxic Events (OAEs) is preserved in the southern high...

Digital elevation and magnetic data from the southern Victorian basins (Otway, Port Phillip, Gippsland Basins) have enabled the recognition of a vast Late Miocene – Pliocene strandplain succession that is a correlative of the Murray Basin Loxton – Parilla strandplain. A combination of ferricrete formation and erosional dissection has made the stran...

The in situ stress field of south-eastern Australia inferred from earthquake focal mechanisms and bore-hole breakouts is unusual in that it is characterised by large obliquity between the maximum horizontal compressive stress orientation (SHmax) and the absolute plate motion azimuth. The evolution of the neotectonic strain field deduced from histor...

Carbonate-sulphide cement stratigraphic relationships in the host rock and ore have been used to constrain the age of mineralisation at the Silvermines zinc-lead-barium deposit. The base-metal sulphides post-date planar dolomite and replace stylolites. Furthermore, the pre-mineralisation planar dolomites also replace stylolites. These and other dia...