Carbon- and oxygen-isotope records of mid-Cretaceous Tethyan pelagic sequences from the Umbria – Marche and Belluno Basins (Italy)

Gambacorta, Gabriele; Jenkyns, Hugh C.; Russo, Fabio; Tsikos, Harilaos; Wilson, Paul A.; Faucher, Giulia; Erba, Elisabetta

doi:10.1127/nos/2015/0066

Cited by 74 publications

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“…The distinctive positive excursions of OAE 1d (latest Albian), the MCE I (middle Cenomanian), and OAE 2 (latest Cenomanian) were unambiguously identified. Comparison with the stratotype section at Pueblo (Colorado) and other classical litho‐chemo‐biostratigraphic records allowed the identification of hiatuses in the studied sections [ Gambacorta et al, ]. In particular, detailed δ 13 C profiles through the Bonarelli Level detected 160–510 kyr long hiatuses eliding the middle to upper part of the characteristic carbon isotope excursion and part of the following interval.…”

Section: Methodsmentioning

confidence: 57%

“…The Plenus Cold Event interrupted formation of dense saline water masses and favored the deposition of black shales in the Umbria‐Marche Basin. The upper part of the Bonarelli Level, correlatable to peak “b” of the δ 13 C anomaly [ Gambacorta et al, ], is characterized by alternating radiolarian layers and black shales chert (Figure ), suggesting the reactivation of intermittent effective bottom currents under greenhouse conditions.…”

Section: Discussionmentioning

confidence: 85%

“…Comparison of the carbon (δ 13 C carb in black and δ 13 C org in green) and oxygen isotope profile for the OAE 2 interval at Eastbourne (England) [ Tsikos et al, ] and at Furlo [ Gambacorta et al, ]. The position of the Bonarelli Level is indicated by a grey band and the OAE 2 anomaly by a yellow band.…”

Section: Discussionmentioning

confidence: 99%

“…Carbon and oxygen isotopic data, integrated with nannofossil biostratigraphy, allowed precise dating and correlation of the selected sections [ Gambacorta et al, ]. The distinctive positive excursions of OAE 1d (latest Albian), the MCE I (middle Cenomanian), and OAE 2 (latest Cenomanian) were unambiguously identified.…”

Section: Methodsmentioning

confidence: 99%

“…Carbon isotope curve is a smoothed (5 pt moving average) composite from the English Chalk [ Jarvis et al, ]. FO: first occurrence and LO: last occurrence (after Gambacorta et al []). Full names of nannofossil species are as follows: Lucianorhabdus maleformis , Eiffellithus eximius, Kamptnerius magnificus, Rhagodiscus asper, Quadrum gartneri, Axopodorhabdus albianus, Lithraphidites acutus, Cylindralithus biarcus, Microrhabdulus decoratus, Gartnerago segmentatum, Corollithion kennedyi , and Eiffellithus turriseiffelii .…”

Section: Case Historymentioning

confidence: 99%

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Onset and demise of Cretaceous oceanic anoxic events: The coupling of surface and bottom oceanic processes in two pelagic basins of the western Tethys

et al. 2016

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The upper Albian-lower Turonian pelagic successions of the Tethys record processes acting during the onset, core, and recovery from perturbed conditions across oceanic anoxic event (OAE) 1d, OAE 2, and the mid-Cenomanian event I (MCE I) relative to intervening intervals. Five sections from Umbria-Marche and Belluno Basins (Italy) were analyzed at high resolution to assess processes in surface and deep waters. Recurrent facies stacking patterns (SP) and their associations record periods of bottom current activity coupled with surface changes in trophic level. Climate changes appear to have been influential on deep circulation dynamics. Under greenhouse conditions, vigorous bottom currents were arguably induced by warm and dense saline deep waters originated on tropical shelves in the Tethys and/or proto-Atlantic Ocean. Tractive facies postdating intermittent anoxia during OAE 1d and in the interval bracketed by MCE I and OAE 2 are indicative of feeble bottom currents, though capable of disrupting stratification and replenish deep water with oxygen. The major warming at the onset of OAE 2 might have enhanced the formation of warm salty waters, possibly producing local hiatuses at the base of the Bonarelli Level and winnowing at the seafloor. Hiatuses detected at the top of the Bonarelli Level possibly resulted from most effective bottom currents during the early Turonian thermal maximum. Times of minimal sediment displacement correlate with cooler climatic conditions and testify a different mechanism of deep water formation, as further suggested by a color change to reddish lithologies of the post-OAE 1d and post-OAE 2 intervals.

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Section: Methodsmentioning

confidence: 57%

Section: Discussionmentioning

confidence: 85%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Case Historymentioning

confidence: 99%

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Onset and demise of Cretaceous oceanic anoxic events: The coupling of surface and bottom oceanic processes in two pelagic basins of the western Tethys

et al. 2016

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Biogeochemical sulfur cycling during Cretaceous oceanic anoxic events: A comparison of OAE1a and OAE2

2016

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Biogeochemical sulfur cycling has varied widely over geologic time, mainly in response to changes in primary productivity and organic carbon burial, volcanism, weathering, and evaporite deposition. Several of these processes are explicitly linked to discreet (<1.2 Ma) intervals of widespread organic carbon burial, termed oceanic anoxic events (OAEs). During the Cretaceous, there is a highly distinctive ~4‰ negative excursion in the sulfur isotope composition of seawater sulfate (δ34SSO4) that is bracketed by the two most prominent OAEs (OAE1a and OAE2). This excursion lasted for ~25 Ma and has been variously attributed to enhanced volcanism, changes in weathering, evaporite burial, and/or changes in modes of organic carbon remineralization. We present new high‐resolution carbon and sulfur isotope records from carbonate‐associated sulfate and pyrite for OAE1a and OAE2. OAE1a is characterized by a monotonic decrease in δ34SSO4 values. Both negative and positive δ34SSO4 excursions are associated with OAE2. To refine hypotheses for the observed changes in biogeochemical sulfur cycling associated with these events, we use a simple sulfur isotope box model. Both empirical and modeling results indicate that δ34SSO4 variability was dominated by input fluxes during OAE1a, whereas enhanced volcanism, weathering, and pyrite burial controlled δ34SSO4 records during OAE2. Our analysis supports the conclusion that Cretaceous marine sulfate concentrations were much lower than modern concentrations and indicates that increases in marine sulfate occurred at the onset of both events. We conclude that increases in marine sulfate from low background concentrations, in conjunction with other environmental characteristics, contributed to the development of OAEs.

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Sedimentary Mercury Enrichments as a Marker for Submarine Large Igneous Province Volcanism? Evidence From the Mid‐Cenomanian Event and Oceanic Anoxic Event 2 (Late Cretaceous)

Scaife

Ruhl

Dickson

et al. 2017

Geochem Geophys Geosyst

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Oceanic Anoxic Event 2 (OAE 2), during the Cenomanian‐Turonian transition (∼94 Ma), was the largest perturbation of the global carbon cycle in the mid‐Cretaceous and can be recognized by a positive carbon‐isotope excursion in sedimentary strata. Although OAE 2 has been linked to large‐scale volcanism, several large igneous provinces (LIPs) were active at this time (e.g., Caribbean, High Arctic, Madagascan, Ontong‐Java) and little clear evidence links OAE 2 to a specific LIP. The Mid‐Cenomanian Event (MCE, ∼96 Ma), identified by a small, 1‰ positive carbon‐isotope excursion, is often referred to as a prelude to OAE 2. However, no underlying cause has yet been demonstrated and its relationship to OAE 2 is poorly constrained. Here we report sedimentary mercury (Hg) concentration data from four sites, three from the southern margin of the Western Interior Seaway and one from Demerara Rise, in the equatorial proto‐North Atlantic Ocean. We find that, in both areas, increases in mercury concentrations and Hg/TOC ratios coincide with the MCE and the OAE 2. However, the increases found in these sites are of a lower magnitude than those found in records of many other Mesozoic events, possibly characteristic of a marine rather than atmospheric dispersal of mercury for both events. Combined, the new mercury data presented here are consistent with an initial magmatic pulse at the time of the MCE, with a second, greater pulse at the onset of OAE 2, possibly related to the emplacement of LIPs in the Pacific Ocean and/or the High Arctic.

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Carbon- and oxygen-isotope records of mid-Cretaceous Tethyan pelagic sequences from the Umbria – Marche and Belluno Basins (Italy)

Cited by 74 publications

References 0 publications

Onset and demise of Cretaceous oceanic anoxic events: The coupling of surface and bottom oceanic processes in two pelagic basins of the western Tethys

Onset and demise of Cretaceous oceanic anoxic events: The coupling of surface and bottom oceanic processes in two pelagic basins of the western Tethys

Biogeochemical sulfur cycling during Cretaceous oceanic anoxic events: A comparison of OAE1a and OAE2

Sedimentary Mercury Enrichments as a Marker for Submarine Large Igneous Province Volcanism? Evidence From the Mid‐Cenomanian Event and Oceanic Anoxic Event 2 (Late Cretaceous)

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