Gregory J. Retallack

University of Oregon | UO · Department of Earth Sciences

Marine life on Earth is known back to the Archean Eon, when life on land is assumed to have been less pervasive than now. Precambrian life on land can now be tested with stable isotopes because living soil CO2 is isotopically distinct for both carbon and oxygen from both marine and volcanic CO2. Our novel compilation of previously published oxygen...

Ediacaran fossils and sedimentary rocks are controversial for whether they are marine or non-marine, and this study applies the test of light rare earth over heavy rare earth weight ratios (LYREE/HYREE) to a variety of Ediacaran siliciclastic and carbonate fossil matrices. Holocene soils have light-YREE-enriched arrays (LYREE/HYREE>4.8) and modern...

Detrital zircon geochronology has been used to determine provenance, but also gives maximum depositional ages that can constrain other forms of geochronology, such as magnetostratigraphy and pedostratigraphy. Pedostratigraphy and magnetostratigraphy correlate a series of global events by spacing or intensity in a fashion comparable with a commercia...

Nonmarine rocks in sea cliffs of southern California store a detailed record of weathering under tropical conditions millions of years ago, where today the climate is much drier and cooler. This work examines early Eocene (~ 50-55 million-year-old) deeply weathered paleosols (ancient, buried soils) exposed in marine terraces of northern San Diego C...

The geological record encodes the relationship between climate and atmospheric carbon dioxide (CO 2 ) over long and short timescales, as well as potential drivers of evolutionary transitions. However, reconstructing CO 2 beyond direct measurements requires the use of paleoproxies and herein lies the challenge, as proxies differ in their assumptions...

The major evolutionary transition from fish to amphibian included Late Devonian tetrapods that were neither fish nor amphibian. They had thick necks and small limbs with many digits on elongate flexuous bodies more suitable for water than land. Habitats of Devonian tetrapods are of interest in assessing selective pressures on their later evolution...

The Pilbara craton of northwestern Australia is known for what were, when reported, the oldest known microfossils and paleosols on Earth. Both interpretations are mired in controversy, and neither remain the oldest known. Both the microfossils and the paleosols have been considered hydrothermal artefacts: carbon films of vents and a large hydrother...

Nonmarine rocks in sea cliffs of southern California store a detailed record of weathering under tropical conditions millions of years ago, where today the climate is much drier and cooler. This work examines early Eocene (50-55 million-year-old) deeply weathered paleosols (ancient, buried soils) exposed in marine terraces of northern San Diego Cou...

Paleosols are useful evidence of paleoclimates and paleoenvironments independent of fossils. Zhangye Danxia National Geopark of Gansu Province (northwestern China) has been protected for its stunning varicolored badlands of Early Cretaceous (Aptian-Albian) claystones. However, the paleoclimates and paleoenvironments forming such unique succession a...

This comment questions an hypothesis for formation of the ornamental stone “zebra rock” from Ediacaran red shales of northwestern Australia as hydrothermal alteration zones. The hypothesis is falsified by absence of Eu anomalies in REE arrays, lack of associated carbonate, low degree of chemical weathering, associated soluble gypsum, strata concord...

Recently reported specimens of the enigmatic Ediacaran fossil Dickinsonia from Russia show damage and repair that provides evidence of how they grew, and of their biological affinities. Marginal and terminal areas of wilting deformation are necrotic zones separating regenerated growth, sometimes on two divergent axes, rather than a single axis. Nec...

Ferruginous biofilms are a form of preservation of fossil leaves making detailed imprints of venation even in coarse sandstone. In modern examples, the biofilm is robust enough to persist after separation, or rotting of the leaf. The biofilms are created by filamentous, iron-oxidizing bacteria such as Leptothrix and Sphaerotilus, and have distincti...

Terrestrial weathering releases phosphorus and other essential nutrients that fuel life in Earth's surface environments and sustain oxygenic photosynthesis. Despite previous suggestions that major changes in terrestrial chemical weathering might have played a role in the global oxygen cycle in the geological past, little is known about the Earth's...

A geological history of pedogenic salts and their microbiomes can now be reconstructed from a review of thousands of described paleosols ranging in age back 3700 Ma. The current diversity of evaporite minerals within paleosol gypsic (By) horizons may have begun with kieserite (MgSO4.H2O at 3700 Ma), then barite (BaSO4 at 3458 Ma), and gypsum (CaSO4...

Cape Wrath is an apt and evocative name for this storm-swept promontory in extreme northwest Scotland. It is a mountainous land of deep fiords and rocky tops flanked with purple-flowered heath and green soggy mats of Sphagnum moss. Felix Mendelssohn, the Jewish-German composer, captured the mood of these wild, wave-swept coasts well in his overture...

Ancient Eleusis (now Elefsina), celebrated in classical Greece and Rome for its mysteries of Demeter and Persephone (Ceres and Proserpina of the Romans) is now an archeological preserve amid petrochemical plants of the outer suburbs of Athens. I visited in spring, to see the very place where legend has it that Persephone (Proserpina), the goddess o...

Once on a mountaineering trip to Mt Aspiring in a remote part of the South Island of New Zealand, we were lucky enough to have 10 consecutive days of sunny weather, during which we climbed most of the peaks around the Bonar Glacier. This was an unexpected bonus because we anticipated no more than two or three days of climbing weather on such a long...

The idea that life came from soil is arguably the most ancient human view of the origin of life. A cuneiform text dating to 2000 BC from the Sumerian city of Nippur in present-day Iraq, describes a feast of the gods, hosted by Ninmah (mother earth) and Enki (god of the waters). Exuberant from much food and wine, Ninmah created six different kinds o...

Trees and forests have a fossil record extending back some 370 million years to the middle of the Devonian geological period. In addition to fossil logs and leaves, paleosols are also a record of ancient forests. Several kinds of soils today are distinctive of forests: the fertile clayey Alfisols of Indiana’s oak-hickory forests, infertile clayey U...

The ships of the invading Greeks had left. Their seaside camp was abandoned. The Trojans, stunned and surprised at first, celebrated their victory in the long war by dragging into the city the large wooden horse left by the Greeks. In the dead of night, Greeks emerged from the horse and throwing open the city gates to fellow warriors, destroyed the...

We are trained to see life as clean and soil as dirty, but life and soil are not so different. Soils are born and die during catastrophic events such as floods and landslides. Many lives are lost or established by such catastrophes. Between these end points, soils develop and grow by addition of clay and organic matter from maturing populations of...

Most children go through a dinosaur phase. They read avidly about them, draw or color them, or place plastic dinosaur models in sculpted landscapes in the sand-box, or garden. Some of us never grow out of our fascination with dinosaurs and their world, but there is more to dinosaurs than the icon of a plastic figurine, or trading card. Dinosaurs we...

Life on this planet was almost extinguished some 252 million years ago at the boundary between the Permian and ensuing Triassic periods of geological history. This has long been known as the greatest of all discontinuities in the history of life, more catastrophic by far than extinction of dinosaurs and other creatures some 66 million years ago. Gl...

The public image of scientists has changed little over the years, despite increasing scientific and technological literacy. Mad scientists are now portrayed in movies as more greedy and antisocial than ever, consumed with the potential power of their discoveries. Few shed a tear at the violent demise of the brilliant genetic engineer, the quirky co...

Our environment today is “of the people, by the people, and for the people”, in a way that Abraham Lincoln could not have suspected in his well-known aphorism for democratic governance. We are now everywhere, changing everything, not only the buildings and fields around us, but also the air we breathe and the soil beneath our feet. The days when lo...

Soils develop through time, to rhythms like those of daily life, as well as to longer rhythms that have seen the rise and fall of civilizations. The daily rhythm of morning dew and midday sun moistens and then dries the cracks and surface of the soil. Evaporating dew adds to the invigorating chill of morning, whereas bright sun glares back from dry...

This book has been a journey around the world and deep into geological time to test ideas about life and soil in past cycles of global climate change. One guiding idea outlined in Chap. 1 is what I have called the Proserpina Principle: plants cool the planet, but animals warm it. Carbon dioxide I exhale is fixed as carbon by plants of my garden, th...

Outback Australia is a magical land of rocks and paleosols that informs us about landscapes and life of truly remote periods of geological time. The red soil and unrelenting flatness are broken by mere stumps of mountains, worn with age into mythical shapes. The great ribbed turtle-back of Uluru (formerly Ayers Rock) has the grandeur of a Gothic ca...

My own taste in science fiction leans not so much toward the great achievements of intellect created by Isaac Asimov, Philip Dick, or Arthur C. Clarke, but to the pulp fiction comics of the mid-twentieth century with its strong visual imagery. This genre of popular art has been celebrated in the “Star Wars” movies.

For many people soil is dirt, a substance beneath consideration, a nuisance to be eradicated from our lives. But dirt is just soil out of place, like a weed in the garden. There is monotony to house cleaning and ordinariness to the soils in our immediate neighborhood. It is not until you dig, look closely, or travel widely, that the spectacular var...

Devonian evolution of woodlands has been envisaged as a protracted increase in size of vascular plants, which can be reconstructed from fossil stumps and trunks. However, Late Silurian and Early Devonian nematophytes such as Prototaxites would have towered over land plants, including vascular plant trees, in the same fossil plant assemblage, until...

Biological regulation of planetary temperature has been explained with the Daisyworld model, in which reflective-cooling white daises balance absorbing-warming black daisies. This article advances the proposition that cooling "daisies" of Daisyworld represent carbon sequestration and consumption by productive soils and ecosystems, such as grassland...

The so called “boring billion” (1800–800 Ma) of Late Paleoproterozoic and early Mesoproterozoic time can now be reassessed from the evidence of diverse paleosols in the Ruyang Group (1749–1561 Ma) in Henan Province, China. Widespread marine sulfidic facies is the reason for the term “boring billion”, but terrestrial facies and paleosols were far fr...

After the Elatina glaciation of Snowball Earth, at least four distinct glacial advances and sea-level retreats punctuated Ediacaran time: Gaskiers glaciation (580 Ma), Fauquier glaciation (571 Ma), Bou-Azzer glaciation (566 Ma) and Hankalchough glaciation (551 Ma). Tillites or diamictites are commonly controversial, but periglacial paleosols with d...

The Cryogenian Period (717–635 Ma), or ‘Snowball Earth’, was an unusually cool period of Earth history when glaciers extended to low latitudes. Past ideas on causes of this widespread glaciation include increased consumption of atmospheric carbon dioxide by silicate weathering due to continental drift into tropical paleolatitudes, or by voluminous,...

The discovery of Dickinsonia in India allows assessment of biogeographic provinces and plate tectonic reconstructions for the late Ediacaran. The fossils were found in the roof of Auditorium Cave at Bhimbetka Rock Shelters, a UNESCO World Heritage Site for Paleolithic and Mesolithic cave art, near Bhopal, Madhya Pradesh. The fossils are identical w...

The drying power of air, or vapour pressure deficit (VPD), is an important measurement of potential plant stress and productivity. Estimates of VPD values of the past are integral for understanding the link between rising modern atmospheric carbon dioxide (pCO 2 ) and global water balance. A geological record of VPD is needed for paleoclimate studi...

The largest mass extinction in the history of life was during the Late Permian, ca 252 Ma. New evidence from stable isotopic composition and Bk metrics of paleosols from the Late Permian to the Middle Triassic in the southern Karoo Basin of South Africa, reveal at least four atmospheric carbon dioxide spikes, coinciding with extinctions on land and...

Paleosols are characterized with new chemical and petrographic data from the Tonian (776–729 Ma) Chuar Group in the eastern Grand Canyon, Arizona. Paleosols have been discovered at 66 stratigraphic levels in a 1622 m sequence largely of marine shales and thin intertidal stromatolitic dolostones. A purple paleosol association includes gypsum “desert...

Ediacaran to Cambrian red sandstones of the Northern Territory, including Arumbera Sandstone, and Grant Bluff and Central Mount Stuart formations, have been reexamined and sampled in order to reconstruct paleoenvironments from sedimentary facies and paleosols. Sedimentary facies include green-gray calcareous sandstone (Member III of Arumbera Sandst...

Coal balls are calcareous peats with cellular permineralization invaluable for understanding the anatomy of Pennsylvanian and Permian fossil plants. Two distinct kinds of coal balls are here recognized in both Holocene and Pennsylvanian calcareous Histosols. Respirogenic calcite coal balls have arrays of calcite δ¹⁸O and δ¹³C like those of desert s...

Zebra rock is an ornamental stone from the early Ediacaran, Ranford Formation, around and in Lake Argyle, south of Kununurra, Western Australia. It has been regarded as a marine clay, liquid crystal, groundwater alteration, unconformity paleosol or product of acid sulfate weathering. This study supports the latter hypothesis and finds modern analog...

Over the past decade, we recorded exact locations of in situ fossils and measured calcareous nodules in paleosols of the Oligocene and lower Miocene (Whitneyan–Arikareean) John Day Formation of Oregon. These data enable precise biostratigraphy within an astronomical time scale of Milankovitch obliquity cycles and also provide mean annual precipitat...

Problematic fossils are described from Late Ediacaran to Early Cambrian red sandstones of the Arumbera Sandstone, Grant Bluff, and Central Mount Stuart Formations in central Australia, within a new systematic classification of Vendobionta. Arumberia banksi has been one of the most problematic of Ediacaran fossils, at first considered a fossil and t...

The accuracy of CO2 hindcasting using fossil Ginkgo stomatal index is ripe for revision for three reasons: exponential rise in atmospheric CO2 over the past decade, discovery of a Kew herbarium specimen of Ginkgo picked in 1754, and increased sophistication of a pedogenic CO2 paleobarometer as an independent parallel record. Past mass extinctions c...

Two upper Middle Permian palaeosols, consisting of coal and pyrite intercalated with a 20 cm thick limestone, were found near Mount Emei in the SW Sichuan Basin, China. The macro- and micromorphology and physico-chemical properties, in conjunction with the mineralogical composition of the palaeosol horizons were investigated. This type of palaeosol...

Soil is defined by the Soil Science Society of America as the natural unconsolidated mineral or organic material on the immediate surface of the Earth produced by biological, chemical, or physical weathering. Soil has been subjected to, and shows effects of, genetic and environmental factors of: climate (including water and temperature effects), an...

Boron content is an indicator of paleosalinity for Mesozoic and Cenozoic clayey sediments, but is compromised by clay diagenesis in deeply-buried sediments of Paleozoic and Ediacaran age. This study of North American, Russian, and Australian, Paleozoic and Ediacaran fossils showed tight covariance of B (ppm) and K (wt%), confirming common wisdom th...

Soils at ancient Greek temples in Greece are distinct for each deity, reflecting an economic basis for their cults, but did this pattern also extend to classical Greek colonies? This study of 24 temples in southern Italy reveals little assimilation by Greek colonists of indigenous cults at first, because their temples are on the same kinds of soils...

Interflag sandstone laminae are thin, silty to sandy, layers between thicker sandstone beds, and a new name for sedimentary structures recently called “shims”, and “microbial mat sandwiches”, from Ediacaran fossil localities of Nilpena, South Australia. They have been regarded as structures unique to Precambrian marine environments, but both the ag...

Paleosols have been discovered in the late Devonian (Famennian) Shaliushui Formation near Pingchuan City, Gansu province, China, and are recognized by evidence of root traces, soil horizons and soil structures. Root traces are remnants of substantial woody plants, reaching deeply within profiles as clayey infills and as drab-haloed root traces. Soi...

SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP Citation for this article: Retallack, G. J., J. M. Theodor, E. B. Davis, S. S. B. Hopkins, and P. Z. Barrett. 2018. First dinosaur (Ornithopoda) from Early Cretaceous (Albian) of Oregon, U.S.A. Journal of Vertebrate Paleontology. DOI: 10.108...

A lens of black schist within 3.7 Ga quartzites of Greenland may be Earth's oldest known alluvial paleosol. The suspect metamorphic rock is a lens in orthoquartzite of berthierine schist with crystals of ripidolite, but it has a truncated top above dark gray grading down to gray color, ptygmatically folded surface cracks filled with silt grains, an...

A back to the future approach to climate change refines Neogene records of paleoclimatic cooling and drying as future climate states for a warming world. Near Alcoota station in central Australia is a late Miocene fossil mammal site for Alcoota (10 Ma) and Ongeva (8 Ma) local faunas. The Alcoota fauna includes the largest known land bird (Dromornis...

Retallack, G.J., May 2018. Leaf preservation in Eucalyptus woodland as a model for sclerophyll fossil floras. Alcheringa xxx, xxx–xxx. A comparison of 29 identifiable vascular plant species in litter beneath Eucalyptus woodland with at least 74 species living nearby showed that the litter is a poor representation of standing vegetation. The leaf li...

Behavior of Columbian mammoths (Mammuthus columbi) is revealed by a newly discovered trackway at the Pleistocene locality of Fossil Lake, Oregon. Our 8 by 20 m excavation of the mammoth trackway found 117 tracks, including one 20-m-long adult trail, partial trackways of 3 additional adults, a yearling and a baby all heading generally west. The trac...

The history of the growth of continental crust is uncertain, and several different models that involve a gradual, decelerating, or stepwise process have been proposed¹⁻⁴. Even more uncertain is the timing and the secular trend of the emergence of most landmasses above the sea (subaerial landmasses), with estimates ranging from about one billion to...

The monsoonal paleoclimate of India has been critical for understanding the tectonic history of Himalayan and Tibetan uplift over the past 60 My. Monsoonal circulation in deep time has been inferred from variation in stable isotopes of tooth enamel, diatom blooms, and dust influx in the Indian Ocean and the advent of C4 grasses, but these proxies a...

Protonympha is an enigmatic fossil represented by two species from the Middle Devonian (Protonympha transversa) and Late Devonian (Protonympha salicifolia) of New York. Although interpreted in the past as a polychaete worm or starfish arm, Protonympha is not found with marine fossils, but with fossil plants. This fossil plant community was a swamp...

Subaerial volcanic flank and floodplain facies of the 3.46. Ga Panorama Formation have been recognized on the basis of trough cross-bedded sandstones, lapilli tuffs, and abundant nodularized barite sand crystals, like those noted in other Archean non-marine facies. These barite-nodular layers are interpreted as alluvial paleosols for the following...

Liu (2016) provides elegant evidence for pyritization of bedding planes at Ediacaran fossil localities of Newfoundland, but fails to demonstrate the ‘death mask' model of moldic preservation for two reasons. First, his petrographic thin sections do not include unpyritized fossils beneath the pyrite, so that his field observations of pyritized fossi...

Coastal-plain paleosols in the 3.0 Ga Farrel Quartzite of Western Australia have organic surface (A horizon) and sulfate-rich subsurface (By) horizons, like soils of the Atacama Desert of Chile, Dry Valleys of Antarctica, and 3.7 Ga paleosols of Mars. Farrel Quartzite paleosols include previously described microfossils, permineralized by silica in...

Palaeosols are ancient soils formed in sedimentary successions between events of sedimentation, erosion and volcanic activity. Soil formation is regulated by circumstances of climate, vegetation, topographic relief, parent material and time. These factors are quantified by nomopedology, in the form of climofunctions, chronofunctions and other relat...

Retallack, G.J., June 2016. Ediacaran fossils in thin-section. Alcheringa 40, xx–xx. ISSN 0311-5518 Megafossils from the Ediacaran Period (635–541 Ma) have been controversial in part because many are mere impressions in coarse-grained rocks. New examination of these fossils in petrographic thin-sections reveals various features that inform understa...

Although Precambrian (>550 Ma old) landscapes have been largely considered devoid of life and do not yield obvious traces indicative of terrestrial fossils (e.g., plant roots), there is now ample evidence for pervasive and diverse microbial communities on land billions of years before the Phanerozoic. Modern “biological soil crusts” or “biocrusts”...

The conventional wisdom of vintners is that alkalinity, and thus less sour and more rounded taste, are enhanced in wine and grapes challenged by low-nutrient soils. A common thread here is pH, an objectively measurable variable that is both a part of wine taste and a proxy for soil fertility. The role of low-pH soils is supported by metadata on Ore...

Not a single paleosol had been described from rocks of Ediacaran age until 2011, but 354 Ediacaran paleosols have been described by 20 different authors since then. Some of these newly recognized paleosols have proven controversial, so this paper reviews 20 distinct tests to determine whether a particular Ediacaran bed could be a paleosol, or not....

Ediacaran fossils of Mistaken Point and other localities in Newfoundland have been reconstructed as denizens of a deep, dark ocean, based on a turbidite interpretation of their sedimentary context. Objections to this view include geochemical indications of fresh water and volcanological and sedimentological evidence that they lived in soils of coas...

Microbially induced sedimentary structures (MISSs) are common in siliciclastic shallow marine settings following the end-Permian mass extinction, but have been rarely reported in terrestrial ecosystems. Here, we present six types of well-preserved MISSs from the upper Sunjiagou Formation and lower Liujiagou Formation of Induan (Early Triassic) age...

Protonympha is an enigmatic fossil represented by two species from the Middle ( P. transversa) and Late Devonian ( P. salicifolia) of New York. Although interpreted in the past as a polychaete worm or starfish arm, Protonympha is not found with marine fossils, but with fossil plants of a community dominated by lycopsids. This community was a swamp...

The global Late Ediacaran Shuram–Wonoka carbon isotope anomaly has been regarded as the largest and longest known isotopic anomaly in the ocean, assuming that all Ediacaran carbonate is marine. Disregarding carbonate in South Australia shown here to be palaeosol or palaeokarst, the synchronous marine organic–carbonate excursion is only −8‰ for δ13C...