There are no confirmed microfossils older than 3,500 million years (Myr) on Earth, probably because of the highly metamorphosed nature of the oldest sedimentary rocks 1 . Therefore, studies have focused almost exclusively on chemical traces and primarily on the isotopic composition of carbonaceous material,which has led to controversies regarding the origin of isotopically light reduced carbon 2 . Schists from the approximately 3,700-Myr-old Isua supracrustal belt in southwest Greenland contain up to 8.8 wt% graphitic carbon that is depleted in 13 C, and this depletion has been attributed to biological activity 3,4 . However, because non-biological decarbonation reactions and Fischer-Tropsch-type synthesis 5 can produce reduced Page 1 of 11 carbon with similar isotopic compositions, non-biological interpretations are possible 2 . Apatite with graphite coatings, within iron formations from the ca. 3,830-Myr-old Akilia supracrustal belt in southwest Greenland has been interpreted as the metamorphosed product of biogenic matter 6 , supported by the presence of biologically important heteroatoms within the graphite 7,8 . However, it has been suggested that some graphite in the Akilia iron formations was deposited by metamorphic fluids 8,9 . This latter interpretation is echoed in the Nuvvuagittuq supracrustal belt (NSB) by the presence of poorly crystalline, fluid-deposited graphite that coats apatite 10 , demonstrating that some apatite-graphite occurrences are produced abiotically during fluid remobilization and high-grade metamorphism.The NSB in northeastern Canada represents a fragment of the Earth's primitive mafic oceanic crust.The NSB is composed predominantly of basaltic metavolcanic rocks (Extended Data Fig. 1 Data Fig. 2). The presence of well-preserved, 20-3,000-µm chalcopyrite crystals within the NSB jasper and carbonate iron formations (Extended Data Fig. 3a) demonstrate the lack of postdepositional oxidation.Most NSB rocks were subjected to upper amphibolite-facies metamorphism around 2,700 Myr ago 14,20 . Here we describe parts of the NSB that were less affected by deformation (Supplementary Table 4) and focus on sites where metamorphic grade appears not to have exceeded lower amphibolite facies 17 . This setting is evidenced by local outcrops in the southwestern margins of the belt that preserve primary chert, diagenetic calcite rhombohedra with poikilitic textures, and minerals of low metamorphic grade such as euhedral stilpnomelane and minnesotaite in chert that lack pseudomorphic retrograde textures.

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The end-Pliensbachian extinction event (187 Ma) has been interpreted either as one of 10 global periodically recurring mass extinctions of the past 250 m.y. or as a minor localized European event. Elevated levels of family extinction spanned five ammonite zones during the late Pliensbachian and the early Toarcian, an interval of ϳ7.5 m.y., and were distributed unequally in the Boreal, Tethyan, and Austral realms. Detailed sampling of invertebrate macrofaunas through complete expanded sequences in northwest Europe shows that most species extinctions occurred in the early Toarcian, following a regional anoxic event. The Early Jurassic mass-extinction event took place over a long time scale, and it was global in extent.

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Fe oxide deposits are commonly found at hydrothermal vent sites at mid-ocean ridge and back-arc sea floor spreading centers, seamounts associated with these spreading centers, and intra-plate seamounts, and can cover extensive areas of the seafloor.

The Pliensbachian-Toarcian (Early Jurassic) fossil record is an archive of natural data of benthic community response to global warming and marine long-term hypoxia and anoxia. In the early Toarcian mean temperatures increased by the same order of magnitude as that predicted for the near future; laminated, organic-rich, black shales were deposited in many shallow water epicontinental basins; and a biotic crisis occurred in the marine realm, with the extinction of approximately 5% of families and 26% of genera. High-resolution quantitative abundance data of benthic invertebrates were collected from the Cleveland Basin (North Yorkshire, UK), and analysed with multivariate statistical methods to detect how the fauna responded to environmental changes during the early Toarcian. Twelve biofacies were identified. Their changes through time closely resemble the pattern of faunal degradation and recovery observed in modern habitats affected by anoxia. All four successional stages of community structure recorded in modern studies are recognised in the fossil data (i.e. Stage III: climax; II: transitional; I: pioneer; 0: highly disturbed). Two main faunal turnover events occurred: (i) at the onset of anoxia, with the extinction of most benthic species and the survival of a few adapted to thrive in low-oxygen conditions (Stages I to 0) and (ii) in the recovery, when newly evolved species colonized the re-oxygenated soft sediments and the path of recovery did not retrace of pattern of ecological degradation (Stages I to II). The ordination of samples coupled with sedimentological and palaeotemperature proxy data indicate that the onset of anoxia and the extinction horizon coincide with both a rise in temperature and sea level. Our study of how faunal associations co-vary with long and short term sea level and temperature changes has implications for predicting the long-term effects of “dead zones” in modern oceans.

Whales are unique among vertebrates because of the enormous oil reserves held in their soft tissue and bone. These 'biofuel' stores have been used by humans from prehistoric times to more recent industrialscale whaling. Deep-sea biologists have now discovered that the oily bones of dead whales on the seabed are also used by specialist and generalist scavenging communities, including many unique organisms recently described as new to science. In the context of both cetacean and deep-sea invertebrate biology, we review scientific knowledge on the oil content of bone from several of the great whale species: Balaenoptera musculus, Balaenoptera physalus, Balaenoptera borealis, Megaptera novaeangliae, Eschrichtius robustus, Physeter macrocephalus and the striped dolphin, Stenella coeruleoalba. We show that data collected by scientists over 50 years ago during the heyday of industrial whaling explain several interesting phenomena with regard to the decay of whale remains. Variations in the lipid content of bones from different parts of a whale correspond closely with recently observed differences in the taphonomy of deep-sea whale carcasses and observed biases in the frequency of whale bones at archaeological sites.