Barite quarry in the “Dresser Formation” of the Pilbara Craton. These rocks are around 3.5 billion years old and contain evidence of microbial life.
Photo: Jan-Peter Duda
Long, long ago, in that dim distant past when Earth was young, and fully 3.5 billion years before creationism's god decided to create a small flat planet with a dome over it centred on the Middle East, thermophile organisms, probably bacteria or archaea were living in a lake in a volcanic caldera in what is now the Pilbara Craton in Western Australia.
This is the conclusion of a research team led by the University of Göttingen wo have just published their work, open access, in the journal, Precambrian Research. Their work is also the subject of a brief news release by the University of Göttingen.
What information do you have on the Pilbara Craton in Western Australia, in particular its age and how it was dated? The Pilbara Craton in Western Australia is one of the oldest pieces of continental crust on Earth, dating back to the Archean Eon. It is estimated to be around 3.6 to 3.8 billion years old, making it one of the most ancient geological formations known.And of course, to the chagrin of creationists, being associated with volcanic activity, the age of this formation can be determined using one of the most accurate and robust geochronologists' dating methods - U-Pb isotope ratios in zircons.
The age of the Pilbara Craton has been determined through various radiometric dating techniques, primarily using zircon crystals found within the rocks of the region. Zircon is a mineral commonly used for dating ancient rocks because it contains trace amounts of uranium, which decays into lead at a known rate. By measuring the ratio of uranium to lead isotopes in zircon crystals, scientists can determine the age of the rocks in which they are found.
In addition to radiometric dating, other methods such as stratigraphic analysis, geochemical analysis, and paleomagnetic studies have also contributed to our understanding of the age and geological history of the Pilbara Craton. These combined methods have provided valuable insights into the early Earth's formation and evolution.
To learn about the first organisms on our planet, researchers have to analyse the rocks of the early Earth. These can only be found in a few places on the surface of the Earth. The Pilbara Craton in Western Australia is one of these rare sites: there are rocks there that are around 3.5 billion years old containing traces of the microorganisms that lived at that time. A research team led by the University of Göttingen has now found new clues about the formation and composition of this ancient biomass, providing insights into the earliest ecosystems on Earth. The results were published in the journal Precambrian Research.
Using high-resolution techniques such as nuclear magnetic resonance spectroscopy (NMR) and near-edge X-ray Absorption Fine Structure (NEXAFS), the researchers analysed carbonaceous particles found rocks made of barium sulphate. This enabled scientists to obtain important information about the structure of microscopically small particles and show that they are of biological origin. It is likely that the particles were deposited as sediment in the body of water of a “caldera” – a large cauldron-shaped hollow that forms after volcanic activity. In addition, some of the particles must have been transported and changed by hydrothermal waters just beneath the surface of the volcano. This indicates a turbulent history of sediment deposits. By analysing various carbon isotopes, the researchers concluded that different types of microorganisms were already living in the vicinity of the volcanic activity, similar to those found today at Icelandic geysers or at hot springs in Yellowstone National Park.
The study not only sheds light on the Earth's past, but is also interesting from a methodological point of view. First author Lena Weimann, Göttingen University’s Geosciences Centre, explains:It was very exciting to be able to combine a range of high-resolution techniques, which enabled us to derive information about the history of how the organic particles were deposited and their origin. As our findings show, original traces of the first organisms can still be found even from extremely old material.
What is Raman spectroscopy and how is it used by geologists and palaeontologists? Raman spectroscopy is a spectroscopic technique used to study vibrational, rotational, and other low-frequency modes in a system. It relies on the inelastic scattering of monochromatic light, usually from a laser source. When light interacts with a sample, most of it is elastically scattered (Rayleigh scattering), meaning it retains the same energy and wavelength. However, a small fraction of the scattered light undergoes inelastic scattering, resulting in a shift in energy due to the interaction with molecular vibrations or rotations within the sample. This shifted light is called Raman scattered light, and by analyzing its frequency shift, information about the chemical composition, molecular structure, and crystalline structure of the sample can be obtained.The abstract and Introduction to the team's paper gives more detail of this highly technical work.
In geology, Raman spectroscopy is used for various purposes:In paleontology, Raman spectroscopy finds applications in the study of fossils and organic materials:
- Mineral identification: Different minerals have distinct Raman spectra due to their unique crystal structures and chemical compositions. Geologists can use Raman spectroscopy to identify minerals present in rocks and minerals. This identification can aid in understanding the geological history, formation conditions, and alteration processes of rocks.
- Characterization of geological materials: Raman spectroscopy can provide insights into the physical and chemical properties of geological materials such as rocks, soils, sediments, and minerals. This includes determining the presence of specific mineral phases, detecting impurities, studying phase transitions, and assessing the degree of alteration or weathering.
- Analysis of fluid inclusions: Raman spectroscopy can be used to analyze fluid inclusions trapped within minerals. By examining the composition and properties of these fluids, geologists can infer information about the conditions (e.g., temperature, pressure, composition) during mineral formation and alteration.
Overall, Raman spectroscopy is a valuable analytical tool for geologists and paleontologists, providing detailed information about the composition, structure, and history of geological and paleontological materials.
- Identification of biomolecules: Raman spectroscopy can help identify and characterize organic molecules present in fossils, such as proteins, lipids, and pigments. This can provide insights into the composition, preservation, and evolutionary relationships of ancient organisms.
- Assessment of diagenetic alterations: Diagenesis refers to the physical and chemical changes that occur in organic and inorganic materials during the process of fossilization. Raman spectroscopy can be used to study these diagenetic alterations, including the degradation of organic matter and the mineralization of fossils.
- Understanding fossilization processes: By analyzing the mineral phases and organic components of fossils using Raman spectroscopy, paleontologists can gain a better understanding of the processes involved in fossilization, such as permineralization, recrystallization, and replacement.
HighlightsAn additional problem for creationists, on top of the fact that the dating of these volcanic rocks used about the most accurate geochronological method available - Uranium-Lead isotope ratios in zirconium crystals - and one which couldn't conceivably give a false result that made 10,000 years look like 3.5 billion, is the fact that, as extremophiles, these organism were already fairly advanced and almost certainly didn't evolve in the lake in the volcanic caldera but came from elsewhere, which means that their ancestors evolved sometime earlier even than 3.5 billion years ago.
- Black bedded barite from the 3.5 Ga Dresser Formation.
- Hydrothermal cycling of biogenic Paleoarchean organic material.
- High-resolution structural analysis of carbonaceous matter (NEXAFS, NMR)
Abstract
Carbonaceous matter (CM) in Archean rocks represents a valuable archive for the reconstruction of early life. Here we investigate the nature of CM preserved in ∼ 3.5 Ga old black bedded barites from the Dresser Formation (Pilbara Carton, Western Australia). Using light microscopy and high-resolution Raman mapping, three populations of CM were recognized: (i) CM at the edges of single growth bands of barite crystals (most frequent), (ii) CM within the barite matrix, and (iii) CM in 50–300 μm wide secondary quartz veins that cross-cut the black bedded barite. Raman spectra of CM inside black bedded barite indicated peak metamorphic temperatures of ∼ 350 °C, consistent with those reached during the main metamorphic event in the area ∼ 3.3 Ga ago. By contrast, CM in quartz veins yielded much lower temperatures of ∼ 220 °C, suggesting that quartz-vein associated CM entered the barite after 3.3 Ga. Near edge X-ray absorption fine structure (NEXAFS) and solid-state nuclear magnetic resonance (NMR) revealed a highly aromatic nature of the CM with a lower aliphatic content, which is in line with the relatively elevated thermal maturity. Catalytic hydropyrolysis (HyPy) did not yield any hydrocarbons detectable with gas chromatography–mass spectrometry (GC–MS). Secondary ion mass spectrometry (SIMS) based δ13C values of individual CM particles ranged from − 33.4 ± 1.2 ‰ to − 16.5 ± 0.6 ‰ and are thus in accordance with a biogenic origin, which is also consistent with stromatolitic microbialites associated with the black bedded barite. Based on these results we conclude that CM at growth bands and inside the barite matrix is syngenetic and only the CM inside quartz veins, which represents a minor portion of the total CM, is a later addition to the system. Furthermore, we discuss different pathways for the input of CM into the barite-forming environment, including the cycling of biological organic material within the hydrothermal system.
1. Introduction
Life’s emergence and early evolution on the young Earth are still incompletely understood. This is in part due to the complicated identification of unambiguous microbial biosignatures in our planet’s oldest rocks (Lepot, 2020, Runge et al., 2022b). Solid carbonaceous matter (CM) preserved in rocks is commonly considered as being derived from organisms and thus may provide a powerful means to track life through deep geological time. However, CM preserved in early Archean rocks might as well have originated from various abiotic sources such as meteorites and/or Fischer-Tropsch type (FTT) synthesis, limiting its applicability as a deep-time biosignature (Brasier et al., 2002, Brasier et al., 2005, De Gregorio et al., 2011, Gourier et al., 2019, Lindsay et al., 2005.1, McCollom et al., 1999, McCollom and Seewald, 2007, Mißbach et al., 2018, Rasmussen and Muhling, 2023, Rushdi and Simoneit, 2001, Sephton, 2002.1). In addition, even the least thermally altered early Archean rocks (Pilbara Craton and Barberton Greenstone Belt) have undergone prehnite-pumpellyite- to lower greenschist-facies metamorphism, complicating matters even further (Hickman, 1983, Terabayashi et al., 2003, Tice et al., 2004). This commonly results in a loss of source-specific CM features such as distinctive molecular structures or uneven distributions of homologs (cf. Mißbach et al., 2016, Vandenbroucke and Largeau, 2007.1). An additional problem is the potential post-depositional emplacement of CM (including hydrocarbons), which is particularly critical in early Precambrian rocks, given their long geological history (Brocks, 2011.1, French et al., 2015, Rasmussen et al., 2008). Despite these challenges, however, some studies were able to detect indigenous molecular compounds in early Archean rocks (Duda et al., 2018.1, Marshall et al., 2007.2, Mißbach et al., 2021, Reinhardt et al., 2024).
Important clues to the earliest life on our planet come from the 3.48 billion-year-old (Ga) Dresser Formation (Pilbara Craton, Western Australia) (van Kranendonk et al., 2008.1), which has been only mildly metamorphosed (prehnite-pumpellyite- to lower greenschist-facies, peak temperatures of ∼ 300 °C) (Delarue et al., 2016.1, Hickman, 1983, Terabayashi et al., 2003). The Dresser Formation belongs to the lower part of the Warrawoona Group and is exposed in the North Pole Dome in Western Australia. It comprises a variety of lithologies, including metavolcanic and metasedimentary rocks and hydrothermal deposits (Buick and Dunlop, 1990, Djokic et al., 2017, Nijman et al., 1998, Runge et al., 2022.1a, van Kranendonk, 2006, van Kranendonk and Pirajno, 2004.1). Hydrothermal veins of the Dresser Formation mainly consist of black chert and barite and permeate pillow basalts of the older North Pole Basalt (Djokic et al., 2021.1, Duda et al., 2018.1, Lindsay et al., 2005.1, Nijman et al., 1998, van Kranendonk et al., 2008.1, van Kranendonk, 2006).
Particularly noteworthy are massive black bedded barite deposits that are spatially associated with stromatolitic microbialites consisting of metal sulfides such as pyrite and sphalerite (i.e., FeS2 and ZnS, respectively) (Baumgartner et al., 2020.1, Baumgartner et al., 2019.1, Harris et al., 2009, Mißbach et al., 2021, Philippot et al., 2007.3, van Kranendonk et al., 2008.1, Walter et al., 1980) (Fig. 1). Regarding the origin of the black bedded barite, early studies suggested a hydrothermally driven replacement of evaporative gypsum deposits that precipitated in a shallow water marine lagoon (Barley et al., 1979, Buick and Dunlop, 1990, Dunlop and Groves, 1978). More recent work, however, has proposed direct precipitation of barite from hydrothermal fluids (Runnegar et al., 2001.1) in a subaquatic volcanic caldera environment (Lindsay et al., 2005.1, Mißbach et al., 2021, Nijman et al., 1998, Ueno, 2007.4, van Kranendonk et al., 2008.1, van Kranendonk, 2006, van Kranendonk et al., 2001.2, van Kranendonk and Pirajno, 2004.1).
Barite is highly stable across a broad range of temperature, pressure, and redox conditions and only poorly soluble (Griffith and Paytan, 2012, Hanor, 2000), making it a promising target for studies of Archean CM. Barites of the Dresser Formation contain various amounts of CM, with total organic carbon (TOC) contents of up to 0.31 wt% (Mißbach et al., 2021). Organic-rich portions show a distinct dark-grey to black color and are therefore termed “black barite” (cf. Mißbach et al., 2021). Furthermore, the black bedded barites preserve abundant primary fluid inclusions (Harris et al., 2009) containing various indigenous carbon-bearing gases such as CO2, COS, CH4, and numerous volatile organic molecules (Mißbach et al., 2021). This is of great geobiological relevance since these compounds may have have been available in the outflowing hydrothermal fluids and fueled microbial communities associated with the barite deposits (Mißbach et al., 2021). The origin of these organic molecules could be due to the large-scale hydrothermally driven redistribution of organic matter in early Archean subaquatic systems (“Hydrothermal Pump Hypothesis”: Duda et al. (2018.1)). However, the nature of CM in the Dresser barites and its relation to these processes is still poorly understood.
Fig. 1. Field photos from the study area. At the sampling site (a, b) and its vicinity (c), black bedded barites of the Dresser Formation contain distinct stromatolitic microbialite interbeds. The white dashed line in (a) shows the contact between chert and barite deposits. Note that reddish colors are due to surface weathering of metal sulfide minerals such as pyrite.
Here we investigate the chemical and structural nature of CM in the black bedded barites from the ∼ 3.5 Ga Dresser Formation using a multifaceted analytical approach. This involves various state-of-the-art analytical techniques, including petrographic microscopy, high-resolution Raman spectroscopy, near edge X-ray absorption fine structure (NEXAFS) spectroscopy, solid-state nuclear magnetic resonance (NMR) spectroscopy, secondary ion mass spectrometry (SIMS), and catalytic hydropyrolysis (HyPy) combined with gas chromatography–mass spectrometry (GC–MS). The findings of our study help to reconstruct the nature of an early Archean habitat, including depositional processes and the influence of microbial life.
Just your regular comprehensive refutation of creationism by revealing the real-world facts that run counter to the cult’s foundational dogmas. Another will be along shortly.
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