New drilling of the early Aptian OAE1a: the Cau core (Prebetic Zone, south-eastern Spain)

Abstract. The Cretaceous was punctuated by several episodes of accelerated global change, defined as Oceanic Anoxic Events (OAEs), that reflect abrupt changes in global carbon cycling. The Aptian Oceanic Anoxic Event (OAE1a; 120 Ma) represents an excellent example, recorded in all major ocean basins, and associated with massive burial of organic matter in marine sediments. The OAE1a is concomitant with the "nannoconid crisis", which is characterized by a major biotic turnover, and a widespread demise of carbonate platforms. Many studies have been published over the last decades on OAE1a's from different sections in the world, and provide a detailed C-isotope stratigraphy for the event. Nevertheless, new high-resolution studies across the event are essential to shed light on the precise timing and rates of the multiple environmental and biotic changes that occurred during this critical period of Earth history. Here we present a new drill core recovering an Aptian section spanning the OAE1a in southern Spain. The so-called Cau section was drilled in the last quarter of 2015. The Cau section is located in the easternmost part of the Prebetic Zone (Betic Cordillera), which represents platform deposits of the southern Iberian palaeomargin. The lower Aptian deposits of the Cau section belong to a hemipelagic unit (Almadich Formation), deposited in a highly subsident sector of the distal parts of the Prebetic Platform. Previous work on the early Aptian of the Cau succession has focused on stratigraphy, bioevents, C-isotope stratigraphy, and organic and elemental geochemistry. A more recent study based on biomarkers has presented a detailed record of the pCO2 evolution across the OAE1a (Naafs et al., 2016). All these studies reveal that the Cau section represents an excellent site to further investigate the OAE1a, based on its unusually high sedimentation rate and stratigraphic continuity, the quality and preservation of fossils, and the well-expressed geochemical signatures.

Download Full-text

Bio-chemostratigraphy of the Barremian–Aptian shallow-water carbonates of the southern Apennines (Italy): pinpointing the OAE1a in a Tethyan carbonate platform

Solid Earth Discussions ◽

10.5194/sed-3-789-2011 ◽

2011 ◽

Vol 3 (2) ◽

pp. 789-838 ◽

Cited By ~ 1

Author(s):

M. Di Lucia ◽

M. Mutti ◽

M. Parente

Keyword(s):

Southern Italy ◽

Carbonate Platform ◽

Black Shales ◽

Carbonate Platforms ◽

Southern Apennines ◽

Main Obstacle ◽

Oceanic Anoxic Event ◽

Anoxic Event ◽

Anoxic Events ◽

Isotope Stratigraphy

Abstract. Low resolution and lack of chronostratigraphic calibration of carbonate platform biostratigraphy hinder precise correlation with coeval deep-water successions. This is the main obstacle when studying the record of Mesozoic oceanic anoxic events in carbonate platforms. In this paper we use carbon isotope stratigraphy to produce the first chronostratigraphic calibration of the Barremian–Aptian biostratigraphy of the Apenninic carbonate platform of southern Italy. According to our calibration, the "Selli level" black shales of epicontinental and oceanic basins corresponds in the southern Apenninic carbonate platform to the interval between the "Orbitolina level", characterized by the association of Mesorbitolina parva and Mesorbitolina texana, and the second acme of Salpingoporella dinarica. The biocalcification crisis of nannoconids corresponds to the interval going from the first acme of S. dinarica to just above the top of the "Orbitolina level". Since these bioevents have been widely recognized beyond the Apenninic platform, our calibration can be used to pinpoint the interval corresponding to the Early Aptian oceanic anoxic event in other carbonate platforms of central and southern Tethys.

Download Full-text

Bio-chemostratigraphy of the Barremian-Aptian shallow-water carbonates of the southern Apennines (Italy): pinpointing the OAE1a in a Tethyan carbonate platform

Solid Earth ◽

10.5194/se-3-1-2012 ◽

2012 ◽

Vol 3 (1) ◽

pp. 1-28 ◽

Cited By ~ 38

Author(s):

M. Di Lucia ◽

A. Trecalli ◽

M. Mutti ◽

M. Parente

Keyword(s):

Carbon Isotope ◽

Deep Water ◽

Carbonate Platform ◽

Carbonate Platforms ◽

Δ13c Values ◽

Oceanic Anoxic Event ◽

Strontium Isotope Stratigraphy ◽

Anoxic Event ◽

Anoxic Events ◽

Isotope Stratigraphy

Abstract. Low biostratigraphic resolution and lack of chronostratigraphic calibration hinder precise correlations between platform carbonates and coeval deep-water successions. These are the main obstacle when studying the record of Mesozoic oceanic anoxic events in carbonate platforms. In this paper carbon and strontium isotope stratigraphy are used to produce the first chronostratigraphic calibration of the Barremian-Aptian biostratigraphy of the Apenninic carbonate platform of southern Italy. According to this calibration, the segment of decreasing δ13C values, leading to the negative peak that is generally taken as the onset of the Selli event, starts a few metres above the last occurrence of Palorbitolina lenticularis and Voloshinoides murgensis. The following rise of δ13C values, corresponding to the interval of enhanced accumulation of organic matter in deep-water sections, ends just below the first acme of Salpingoporella dinarica, which roughly corresponds to the segment of peak δ13C values. The whole carbon isotope excursion associated with the oceanic anoxic event 1a is bracketed in the Apenninic carbonate platform between the last occurrence of Voloshinoides murgensis and the "Orbitolina level", characterized by the association of Mesorbitolina parva and Mesorbitolina texana. Since these bioevents have been widely recognized beyond the Apenninic platform, the calibration presented in this paper can be used to pinpoint the interval corresponding to the Early Aptian oceanic anoxic event in other carbonate platforms of central and southern Tethys. This calibration will be particularly useful to interpret the record of the Selli event in carbonate platform sections for which a reliable carbon isotope stratigraphy is not available.

Download Full-text

Carbon-isotope and microfaunal stratigraphy bounding the Lower Aptian Oceanic Anoxic Event 1a in northeastern Tunisia

Cretaceous Research ◽

10.1016/j.cretres.2012.05.011 ◽

2013 ◽

Vol 39 ◽

pp. 133-148 ◽

Cited By ~ 16

Author(s):

Abdallah Elkhazri ◽

Hassen Abdallah ◽

Saloua Razgallah ◽

Michel Moullade ◽

Wolfgang Kuhnt

Keyword(s):

Carbon Isotope ◽

Oceanic Anoxic Event ◽

Lower Aptian ◽

Anoxic Event ◽

Northeastern Tunisia

Download Full-text

A new record of the Toarcian oceanic anoxic event from Scotland (UK) and environmental responses

10.5194/egusphere-egu21-893 ◽

2021 ◽

Author(s):

Wenhan Chen ◽

David Bryan Kemp ◽

Tianchen He ◽

Chunju Huang

Keyword(s):

Chemical Weathering ◽

Coarse Grained ◽

Global Ocean ◽

Geochemical Data ◽

Oceanic Anoxic Event ◽

Organic Carbon Isotope ◽

Anoxic Event ◽

Geographic Differences ◽

Environmental Responses ◽

Global Carbon

<p>The early Toarcian oceanic anoxic event (T-OAE, ~183 Ma) was characterized by a prominent environmental perturbation, likely associated with a large amount of <sup>12</sup>C-enriched carbon released into the global ocean-atmosphere system. This effusion caused a marked disruption to the global carbon cycle and propagated a series of remarkable changes in ocean chemistry and climate. Although the T-OAE has been recognized worldwide, clear geographic differences in the character of the event and its environmental effects have been recognized. Here, we present new geochemical data from a lower Toarcian succession on the Isle of Raasay, NE Scotland (Hebrides Basin, Northwest European Shelf). Organic carbon isotope data through the Raasay section reveal a pronounced negative excursion, similar to that recognised globally. The excursion interval is enriched in organic matter, and redox sensitive element data suggest that suboxic bottom water conditions contemporaneously occurred, likely interspersed with anoxic episodes. Our findings contrast with evidence of more pervasive anoxia/euxinia in nearby basins, and emphasize how deoxygenation was spatially variable within the T-OAE. Inorganic geochemical data and sedimentological observations suggest a significant enhancement in chemical weathering and coarse-grained detrital flux during the T-OAE on Raasay. These findings support evidence from other localities for a strengthening of hydrological cycling in response to global warming during the T-OAE.</p>

Download Full-text

Sedimentology, Petrology, and Volcanology of the Lower Aptian Oceanic Anoxic Event (OAE1a), Shatsky Rise, North-Central Pacific Ocean

10.2973/odp.proc.sr.198.109.2005 ◽

2005 ◽

Author(s):

K.M. Marsaglia

Keyword(s):

Pacific Ocean ◽

Central Pacific ◽

Shatsky Rise ◽

North Central ◽

Oceanic Anoxic Event ◽

Central Pacific Ocean ◽

Lower Aptian ◽

Anoxic Event

Download Full-text

Central Tethyan platform-top hypoxia during Oceanic Anoxic Event 1a

Climate of the Past ◽

10.5194/cp-15-1327-2019 ◽

2019 ◽

Vol 15 (4) ◽

pp. 1327-1344 ◽

Cited By ~ 5

Author(s):

Alexander Hueter ◽

Stefan Huck ◽

Stéphane Bodin ◽

Ulrich Heimhofer ◽

Stefan Weyer ◽

...

Keyword(s):

Trace Elements ◽

Shallow Water ◽

Oxygen Depletion ◽

Water Masses ◽

Time Resolved ◽

Oceanic Anoxic Event ◽

Driving Mechanisms ◽

Lower Aptian ◽

Anoxic Event ◽

Coral Communities

Abstract. Short-term hypoxia in epeiric water masses is a common phenomenon of modern marine environments and causes mass mortality in coastal marine ecosystems. Here, we test the hypothesis that during the early Aptian, platform-top hypoxia temporarily established in some of the vast epeiric seas of the central Tethys and caused, combined with other stressors, significant changes in reefal ecosystems. Potentially interesting target examples include time intervals characterized by the demise of lower Aptian rudist–coral communities and the establishment of microencruster facies, as previously described from the central and southern Tethys and from the proto-North Atlantic domain. These considerations are relevant as previous work has predominantly focused on early Aptian basinal anoxia in the context of Oceanic Anoxic Event (OAE) 1a, whereas the potential expansion of the oxygen minimum zone (OMZ) in coeval shallow-water environments is underexplored. Well-known patterns in the δ13C record during OAE 1a allow for a sufficiently time-resolved correlation with previously studied locations and assignment to chemostratigraphic segments. This paper presents and critically discusses the outcome of a multi-proxy study (e.g., rare earth elements (REEs), U isotopes, and redox-sensitive trace elements) applied to lower Aptian shallow-water carbonates today exposed in the Kanfanar quarry in Istria, Croatia. These rocks were deposited on an extensive, isolated high in the central Tethys surrounded by hemipelagic basins. Remarkably, during chemostratigraphic segment C2, the depletion of redox-sensitive trace elements As, V, Mo, and U in platform carbonates, deposited in normal marine oxic waters, record the first occurrence of basinal, organic-rich sediment deposition in which these elements are enriched. During the C3 segment, seawater oxygen depletion established on the platform top as indicated by the patterns in Ce/Ce* and U isotopes. Shifts in redox-sensitive proxies coincide with the expansion of microencruster facies. Segment C4 witnesses the return to normal marine reefal faunas on the platform top and is characterized by patterns in redox-sensitive proxies typical of normal marine dissolved oxygen levels. It remains unclear, however, if platform-top hypoxia resulted from the expansion and upwelling of basinal, oxygen-depleted water masses or if spatially isolated, shallow hypoxic water bodies formed on the platform. Data shown here are relevant as they shed light on the driving mechanisms that control poorly understood faunal patterns during OAE 1a in the neritic realm and provide evidence on the intricate relation between basinal and platform-top water masses.

Download Full-text