Major Carbon Cycle Perturbations Research Articles

Frequency modulation reveals the phasing of orbital eccentricity during Cretaceous Oceanic Anoxic Event II and the Eocene hyperthermals

Abstract Major advances in our understanding of paleoclimate change derive from a precise reconstruction of the periods, amplitudes and phases of the ‘Milankovitch cycles’ of precession, obliquity and eccentricity. While numerous quantitative approaches exist for the identification of these astronomical cycles in stratigraphic data, limitations in radioisotopic dating, and instability of the theoretical astronomical solutions beyond ∼50 Myr ago, can challenge identification of the phase relationships needed to constrain climate response and anchor floating astrochronologies. Here we demonstrate that interference patterns accompanying frequency modulation (FM) of short eccentricity provide a robust basis for identifying the phase of long eccentricity forcing in stratigraphic data. One- and two-dimensional models of sedimentary distortion of the astronomical signal are used to evaluate the veracity of the FM method, and indicate that pristine eccentricity FM can be readily distinguished in paleo-records. Apart from paleoclimatic implications, the FM approach provides a quantitative technique for testing and calibrating theoretical astronomical solutions, and for refining chronologies for the deep past. We present two case studies that use the FM approach to evaluate major carbon-cycle perturbations of the Eocene and Late Cretaceous. Interference patterns in the short-eccentricity band reveal that Eocene hyperthermals ETM2 (‘Elmo’), H2, I1 and ETM3 (X; ∼52–54 Myr ago) were associated with maxima in the 405-kyr cycle of orbital eccentricity. The same eccentricity configuration favored regional anoxic episodes in the Mediterranean during the Middle and Late Cenomanian (∼94.5–97 Myr ago). The initial phase of the global Oceanic Anoxic Event II (OAE II; ∼93.9–94.5 Myr ago) coincides with maximum and falling 405-kyr eccentricity, and the recovery phase occurs during minimum and rising 405-kyr eccentricity. On a Myr scale, the event overlaps with a node in eccentricity amplitudes. Both studies underscore the importance of seasonality in pacing major climatic perturbations during greenhouse times.

A climatic control on reorganization of ocean circulation during the mid-Cenomanian event and Cenomanian-Turonian oceanic anoxic event (OAE 2): Nd isotope evidence

Although ocean circulation plays a vital role in the climate system, its response to major carbon-cycle perturbations during the mid-Cretaceous, including mid-Cenomanian event I (MCE I) and the Cenomanian-Turonian oceanic anoxic event (OAE 2), is poorly constrained. Here we present Nd isotope evidence for episodic increases in the influence of boreal seawater in the European epicontinental sea during MCE I. The start of this circulation reorganization lagged the onset of the δ13C positive excursion defining MCE I. This sequence of change is similar to that observed during OAE 2 in the same area, showing a consistent response of regional circulation to changes in the global carbon cycle. Brief intervals of invasion of boreal fauna to mid-latitude seas, two during MCE I and one during OAE 2 (Plenus cold event), all started after the influence of boreal seawater was enhanced, implying a slower biological response to climate cooling rather than passive transport of fauna by boreal waters. The lack of an Nd isotope positive excursion in our record across MCE I supports a volcanic origin for prominent increases in seawater Nd isotope values found in the European epicontinental sea and the tropical Atlantic during OAE 2. The observed tight circulation–carbon cycle coupling may help the upper ocean replenish nutrients from deep waters and/or volcanic sources, providing a critical feedback allowing continuation of MCE I and OAE 2 over long durations.

The planktic foraminiferal B/Ca proxy for seawater carbonate chemistry: A critical evaluation

The ratio of boron to calcium (B/Ca) in the carbonate tests of planktic foraminifers has been proposed as a proxy for surface ocean pH or carbonate ion concentration ([CO32−]), with a possible secondary influence of temperature. In both cultured and wild specimens, B/Ca generally increases with [B(OH)4−/HCO3−], consistent with the proxy's theoretical basis. However, close examination of the available data reveals that calibrations using the empirical boron partition coefficient, KD=[B/Ca]calcite/[B(OH)4−/HCO3−]seawater, can be driven by independent relationships between [B(OH)4−/HCO3−] and other environmental parameters, not by B/Ca itself. If the influence of B/Ca on a calibration is negligible, it follows that combining that calibration with down-core B/Ca can not yield new information about past ocean conditions. In this study, we evaluate existing calibrations and down-core records with the aim of establishing a framework that allows consistent calibration methods to yield accurate proxy reconstructions from the fossil record. While many issues still need to be addressed, B/Ca does respond to seawater chemistry, and does change across some major climate transitions. Because it may provide insight into major carbon cycle perturbations, we make specific recommendations on how to tackle current uncertainties and develop B/Ca into a more robust proxy.

Multiple phases of carbon cycle disturbance from large igneous province formation at the Triassic-Jurassic transition

The end-Triassic mass extinction (ca. 201.4 Ma) coincided with a major carbon cycle perturbation, based on an ∼5‰−6‰ negative excursion in δ 13 C TOC (total organic carbon) records. Both events coincided directly with the onset of massive flood basalt volcanism in the Central Atlantic Magmatic Province (CAMP). Organic carbon isotope data from the western Tethys Ocean (Austria) and the Germanic basin (UK and Germany), however, demonstrate earlier disruption of the global carbon cycle, preceding CAMP eruptions. A 2‰−3‰ late Rhaetian precursor negative excursion in marine and continental δ 13 C TOC records is matched by a negative perturbation in δ 13 C leaf data, suggesting multiple events of Rhaetian atmospheric 13 C depletion. Intruding dike and sill systems, preceding CAMP eruptive volcanic activity, may have released ∼3000–7000 Gt of isotopically light carbon as thermogenic methane from subsurface organic-rich strata. This possibly caused an end-Triassic atmospheric p CO 2 increase and reduced ecosystem stability before the actual onset of eruptive volcanic activity in the CAMP region. We present a model that identifies three phases of disturbances in global biogeochemical cycles related to the formation of this large igneous province.

Update of the carbon and oxygen isotopic records of the Early–Late Pliensbachian (Early Jurassic, ~ 187 Ma): Insights from the organic-rich hemipelagic series of the Lusitanian Basin (Portugal)

A high-resolution carbon and oxygen isotopic bulk carbonate record from organic-rich hemipelagic series of Early–Late Pliensbachian age (~ 187 Ma) is presented for the Lusitanian Basin (Portugal) and compared to the record of other sedimentary basins. This dataset provides an excellent basis for discussing newly raised questions concerning the hypothesis of major carbon cycle perturbations prior to the Toarcian Oceanic Anoxic Event. In addition to the recognition in the studied series of two positive carbon isotope excursions previously defined elsewhere, corresponding to the Ibex and Margaritatus (uppermost Stokesi–Gibbosus subzones) zones, a third positive excursion is identified here for the first time, at the Davoei Zone. In the Lusitanian Basin these excursions are associated with organic-rich facies intervals. The younger excursion may be related to worldwide enhanced preservation of organic matter in the Margaritatus Zone. We suggest that until these organic-rich facies are well age constrained at a wider scale and high-resolution carbon data are provided from other locations, and that worldwide anoxia is proven, this interval should be referred to as an Organic Matter Preservation Interval (Late Pliensbachian OMPI). This period is probably linked with the complex chain of events that eventually led to the Toarcian Oceanic Anoxic Event.

Major perturbation in sulfur cycling at the Triassic-Jurassic boundary

Research Article| September 01, 2009 Major perturbation in sulfur cycling at the Triassic-Jurassic boundary Kenneth H. Williford; Kenneth H. Williford 1University of Washington, Seattle, Washington 98195, USA *Current address: Curtin University of Technology, Perth, Australia; E-mail: k.williford@curtin.edu.au. Search for other works by this author on: GSW Google Scholar Julien Foriel; Julien Foriel 1University of Washington, Seattle, Washington 98195, USA Search for other works by this author on: GSW Google Scholar Peter D. Ward; Peter D. Ward 1University of Washington, Seattle, Washington 98195, USA Search for other works by this author on: GSW Google Scholar Eric J. Steig Eric J. Steig 1University of Washington, Seattle, Washington 98195, USA Search for other works by this author on: GSW Google Scholar Geology (2009) 37 (9): 835–838. https://doi.org/10.1130/G30054A.1 Article history received: 21 Jan 2009 rev-recd: 09 Apr 2009 accepted: 28 Apr 2009 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Kenneth H. Williford, Julien Foriel, Peter D. Ward, Eric J. Steig; Major perturbation in sulfur cycling at the Triassic-Jurassic boundary. Geology 2009;; 37 (9): 835–838. doi: https://doi.org/10.1130/G30054A.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Stable sulfur isotopes from the reduced sulfur fraction of Late Triassic–Early Jurassic marine sediments at Kennecott Point in British Columbia, Canada, show evidence for a major perturbation in sulfur cycling coincident with a major carbon cycle perturbation in the wake of a mass extinction event at the Triassic-Jurassic boundary. The δ34S of reduced sulfur shifts from values consistent with open system bacterial sulfate reduction (−30‰) to values higher than any previously reported for Early Jurassic sulfates (20‰) and consistent with complete utilization of sulfate and Rayleigh fractionation in a closed system. We suggest that this isotopic shift was initiated by declining seawater sulfate concentration due to evaporite deposition in nascent Atlantic rift zones and enhanced by a local mechanism, such as a decoupling of the zone of sulfate reduction from the sulfate supply due to a catastrophic increase in the flux of land-derived sediments reaching the sea in the wake of massive terrestrial plant die-off during the Triassic–Jurassic mass extinction. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The end Triassic mass extinction record of Williston Lake, British Columbia

Triassic–Jurassic boundary sections on the shore of Lake Williston, British Columbia record a spectrum of depositional environments from the western Canadian continental margin. A primarily deep-water, anoxic record of deposition, indicated by V/V + Ni, V/Cr, Th/U indices and pyrite framboid and facies data, is seen throughout the Late Triassic–Early Jurassic (Norian-Hettangian) interval in a section at Black Bear Ridge. Abundant Monotis bivalve populations in Norian strata are interpreted to have lived on the seabed during transient oxygenation events that punctuated the background anoxic conditions. Monotis went extinct around the Norian/Rhaetian boundary and the deep-water assemblages are subsequently dominated by thin-shelled pectinids. An intra-Rhaetian sea-level fall generated a major hiatus in the proximal Black Bear Ridge section whilst distinctive lowstand strata were developed in the more distal and more complete Ne Parle Pas Point and Pardonet Creek sections. These consist of shallow-water, phosphatic ooid sand facies that contain diverse bivalves. The majority of the infaunal bivalves (but not the epifaunal ones) disappeared at the acme of the regression. This is the end-Triassic mass extinction event and it occurred shortly before a terminal Triassic flooding event. This transgressive event is associated with a rapid negative shift of δ 13C org values interpreted to be the Initial Isotope Excursion of Hesselbo et al. [Hesselbo, S.P., Robinson, S.A., Surlyk, F., Piasecki, S., 2002. Terrestrial and marine extinction at the Triassic-Jurassic boundary synchronized with major carbon-cycle perturbation: a link to initiation of massive volcanism? Geology 30, 251–254]. The Rhaetian record of Williston Lake thus records an extinction of shallow-water infaunal bivalves during a lowstand prior to the development of a transgressive record that is associated with a major, negative C isotope.

Synchrony between the Central Atlantic magmatic province and the Triassic–Jurassic mass-extinction event?

We present new data and a synthesis of cyclostratigraphic, lithostratigraphic, biostratigraphic, and published magnetostratigraphic and basalt geochemical data from eastern North America and Morocco in an attempt to clarify the temporal relationship between the Triassic–Jurassic mass extinction (∼ 202 Ma) and Earth's largest sequence of continental flood basalts, the Central Atlantic magmatic province (CAMP). Newly discovered zones of reverse polarity within CAMP flow sequences of Morocco have been hypothesized by Marzoli et al. [Marzoli, A., Bertrand, H., Knight, K.B., Cirilli, S., Buratti, N., Vérati, C., Nomade, S., Renne, P.R., Youbi, N., Martini, R., Allenbach, K., Neuwerth, R., Rapaille, C., Zaninetti, L., Bellieni, G., 2004. Synchrony of the Central Atlantic magmatic province and the Triassic–Jurassic boundary climatic and biotic crisis. Geology 32, 973–976.] and Knight et al. [Knight, K.B., Nomade, S., Renne, P.R., Marzoli, A., Betrand, H., Youbi, N., 2004. The Central Atlantic Magmatic Province at the Triassic–Jurassic boundary: paleomagnetic and 40Ar/ 30Ar evidence from Morocco for brief, episodic volcanism. Earth and Planetary Science Letters 228, 143–160.] as correlates of a very short, uppermost Triassic age reverse chron in the Newark basin, thus suggesting that much of the Moroccan CAMP was synchronous with or predates the Triassic–Jurassic boundary. Here, however, we explain these apparent reverse polarity zones as possible correlatives of poorly sampled lower Jurassic basalt flow sequences and overlying strata in eastern North America and lower Jurassic reverse polarity sequences recognized by others in the Paris basin. A revised Milankovitch cyclostratigraphy based on new core and field data constrains the duration of eastern North America basaltic flows to ∼ 610 ky after the Triassic–Jurassic palynological turnover event. Palynological data indicates correlation of the initial carbon isotopic excursion of Hesselbo et al. [Hesselbo, S.P., Robinson, S.A., Surlyk, F., Piasecki, S., 2002. Terrestrial and marine extinction at the Triassic–Jurassic boundary synchronized with major carbon-cycle perturbation: a link to initiation of massive volcanism. Geology 30, 251–254.] at St. Audrie's Bay to the palynological turnover event and vertebrate extinction level in eastern North America, suggesting a revised magnetostratigraphic correlation and robust carbon isotopic tests of the Marzoli–Knight hypothesis. We conclude that as yet there are no compelling data showing that any of the CAMP predated or was synchronous with the Triassic–Jurassic extinction event.

Biostratigraphy and carbon isotope stratigraphy of uppermost Cretaceous‐lower Cenozoic Muzzle Group in middle Clarence valley, New Zealand

Muzzle Group strata exposed along southeast‐flowing tributaries of the Clarence River valley, Marlborough, record hemipelagic‐pelagic sedimentation across a high latitude (c. 55°S), terrigenous sediment‐starved, continental margin from latest Cretaceous to middle Eocene times. Studies of dinoflagellates, foraminifera, calcareous nannofossils, and radiolarians have been integrated with bulk carbonate δ13C profiles to establish the chronostratigraphy for two stratigraphic sections along Bluff and Muzzle Streams, middle Clarence valley. The two sections comprise similar successions. Uppermost Cretaceous (upper Haumurian) micritic limestone of Mead Hill Formation is overlain unconformably by Teredo Limestone, a c. 0.25 m thick bed of highly glauco‐nitic, calcareous sandstone. This unit, the basal member of Amuri Limestone, is overlain conformably by c. 15 m thick Lower Limestone, micritic limestone that is glauconitic at base and progressively more marl‐rich in its upper part. Lower Limestone grades up into Lower Marl, a poorly exposed, 40–70 m thick unit of alternating marl and micritic limestone beds. Biostratigraphy indicates that the base of Amuri Limestone is younger at Bluff Stream (earliest Eocene, early Waipawan) than at Muzzle Stream (late Paleocene, late Teurian). In the condensed (12 m) upper Paleocene‐lower Eocene Amuri Limestone sequence at Muzzle Stream, a trend in δ13C from high (≥2.4‰) to low (≤1‰) values is consistent with global records across three major climate or carbon cycle perturbations: the late Paleocene carbon isotope maximum (PCIM, 59–56 Ma), the initial Eocene thermal maximum (IETM, 55.5 Ma), and the early Eocene climatic optimum (EECO, 53–50 Ma). Probably only the upper PCIM is preserved in the 4 m thick siliceous limestone interval overlying Teredo Limestone. The IETM is well‐defined by a 1‰ negative δ13C excursion at the base of a 0.8 m thick marl‐rich unit (Dee Marl), 5 m above the base of Lower Limestone at Muzzle Stream, and the abrupt appearances of Eocene‐restricted species or distinctly warm‐water elements within dinoflagellate, foraminiferal, calcareous nannofossil, and radiolarian assemblages. The lithological expression of the IETM as a recessive marly unit has now been identified in three Clarence valley sections (Muzzle, Dee, and Mead Streams), representing a 20 km continental margin transect. Sedimentation rate trends across this margin indicate that the local effects of extreme global warming were increased supply of terrigenous mud, probably due to enhanced precipitation, weathering and erosion, and a decrease in pelagic sedimentation, reflecting a decrease in oceanic productivity. Bluff section lacks an IETM record but contains an expanded (20 m) early Eocene succession that records the onset of the EECO as a progressive increase in marl‐rich units associated with consistently low δ13C (<1‰). Both Muzzle and Bluff sections indicate that local environmental changes associated with the EECO were a more gradual and extended version of those inferred for the IETM: an increase in terrigenous mud supply coupled with a decrease in oceanic productivity.

Terrestrial and marine extinction at the Triassic-Jurassic boundary synchronized with major carbon-cycle perturbation: A link to initiation of massive volcanism?

Mass extinction at the Triassic-Jurassic (Tr-J) boundary occurred about the same time (200 Ma) as one of the largest volcanic eruptive events known, that which characterized the Central Atlantic magmatic province. Organic carbon isotope data from the UK and Greenland demonstrate that changes in flora and fauna from terrestrial and marine environments occurred synchronously with a light carbon isotope excursion, and that this happened earlier than the Tr-J boundary marked by ammonites in the UK. The results also point toward synchronicity between extinctions and eruption of the first Central Atlantic magmatic province lavas, suggesting a causal link between loss of taxa and the very earliest eruptive phases. The initial isotopic excursion potentially provides a widely correlatable marker for the base of the Jurassic. A temporary return to heavier values followed, but relatively light carbon dominated the shallow oceanic and atmospheric reservoirs for at least 600 k.y.