Calcareous nannofossil biostratigraphy of an outcrop section of Aptian sediments of west-central Portugal (Lusitanian Basin)

Gama, Rui O.B.P. Da; Bown, Paul R.; Cabral, Maria Cristina

doi:10.1144/jm.28.2.153

Cited by 8 publications

(4 citation statements)

References 15 publications

(35 reference statements)

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“…), which are assumed to be of early Aptian age with the occurrence of caprinid rudists (REY, 1992;BURLA et al, 2008), and 0.707407 to 0.707424 (actually 0.707379 to 0.707450 if acknowledging error bars) for the overlying orbitolinid-bearing beds (Praia de Lagoa Mb.) of late early and/or early late Aptian age (BURLA et al, 2008), that also include angiosperm pollen (HEIMHOFER et al, 2007) and calcareous nannofossils (DA GAMA et al, 2012). The range of values is almost similar for both members and, if plotted onto our compiled curve, it spans most of the upper Barremian and the entire lower Aptian including the "grey band".…”

Section: Estremaduramentioning

confidence: 55%

Is Strontium-isotope stratigraphy a reliable tool for dating shallow-marine platform carbonates at the Barremian-Aptian transition? Review of western Tethyan case studies

Frau¹,

Massé²,

Fenerci-Masse³

et al. 2018

Carnets Geol.

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Strontium-isotope measurements on Lower Cretaceous marine rocks derive from belemnite material sampled in ammonite-constrained basinal successions. A group of values with a narrow range across the Barremian/Aptian boundary does not allow the separation of the uppermost Barremian (Martelites sarasini ammonite zone) from the lower Aptian pro parte (Deshayesites oglanlensis-D. forbesi ammonite zones). Growing numbers of studies applied Sr-Isotope Stratigraphy (SIS) on Barremian-Aptian shallow-marine sequences (Urgonian facies) in order to solve controversial results obtained by using different shallow-water biological time markers. Based on re-examination of case studies, we conclude that Sr-isotope values can neither be used to prove nor to disprove the location of the putative Barremian/Aptian boundary based on biostratigraphy. Pending more data available, SIS should be used with caution for dating ammonite-free carbonate sediments in the corresponding time interval.

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Section: Estremaduramentioning

confidence: 55%

Is Strontium-isotope stratigraphy a reliable tool for dating shallow-marine platform carbonates at the Barremian-Aptian transition? Review of western Tethyan case studies

Frau¹,

Massé²,

Fenerci-Masse³

et al. 2018

Carnets Geol.

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“…The nannofossil biostratigraphy of Da Gama et al . (2009) supports an early Aptian age for the Ponta Alta Member as well but suggests a late Aptian age for the unconformably overlying Praia da Lagoa Member.…”

Section: Geological Settingmentioning

confidence: 71%

Evaluating the role of coastal hypoxia on the transient expansion of microencruster intervals during the early Aptian

Hueter

Huck

Heimhofer

et al. 2021

LET

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Worldwide, a growing number of modern coastal marine ecosystems are increasingly exposed to suboxic‐ or even anoxic conditions. Low seawater oxygen levels trigger significant ecosystem changes and may result in mass mortality of oxygen‐sensitive biota. The applicability of observations from recent (anthropogenically influenced) suboxic coastal settings to fossil anoxic shallow‐marine environments is, however, as yet poorly explored. The test case documented here are upper Barremian to lower Aptian strata in the Lusitanian Basin (Ericeira section, Portugal). These are characterized by the transient demise of rudist–coral communities and the rapid establishment of microencruster facies in the vacant ecological niches. The hypothesis is tested that the temporal expansion of the microencrusting organism Lithocodium aggregatum took place in response to platform‐top seawater oxygen depletion. We critically discuss the outcome of a multi‐proxy palaeoseawater redox approach (e.g. Rare Earth Elements (REEs), U isotopes and palaeoecology) and put the robustness of the proxies applied here to the test. This is done by considering issues with these methods in general but also emphasizing the significance of terrigenous contamination and fractionation effects. Data shown here document that evidence for coastal seawater oxygen depletion in the prelude of Oceanic Anoxic Event (OAE) 1a is lacking, and hence, anoxia was not the driving mechanism for the demise of rudist–coral ecosystems in the proto‐North Atlantic platform setting studied here. In contrast, well‐oxygenated early Aptian platform‐top water masses are proposed for this site. Geologically short (decades to millennia) fluctuations in seawater oxygen levels cannot be excluded, however. But even if these took place, they offer no explanation for the Kyr to Myr‐scale patterns discussed here. The present paper is relevant as it sheds light on the complexity of mechanisms that drive punctuated Early Cretaceous coral–rudist ecosystem turnover, and assess strengths and weaknesses of redox proxies applied to ancient shallow‐marine platform carbonates.

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“…4 and 5). Nannofossil data from the São Julião locality(Da Gama et al, 2009) corroborate an early Aptian age for the Ponta Alta Member and propose a late Aptian age for the unconformably overlyingPraia de Lagoa Member (Figs. 4 and 5).…”

mentioning

confidence: 72%

“…the Ponta Alta Member(Da Gama et al, 2009) points to an age not older than early Aptian for this member (Figs. 4 and 5).…”

mentioning

confidence: 91%

Early Aptian algal bloom in a neritic proto-North Atlantic setting: Harbinger of global change related to OAE 1a?

Huck¹,

Heimhofer²,

Immenhauser³

2012

Geological Society of America Bulletin

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Pervasive growth of microencrusters (Lithocodium/Bacinella) characterizes shortlived stratigraphic intervals in Lower Aptianshallow-water carbonate platform settings of the central and southern Tethys. Although a causal relationship between this peculiar shallow-water facies and the early Aptian oceanic anoxic event (OAE) 1a seems likely, the temporal and spatial distributions of Lithocodium and Bacinella mass occurrences in the rock record point to a rather complex pattern. Possible controls include various global and regional drivers expressed in environmental perturbation of neritic ecosystems. Microencruster blooms have hitherto been reported to occur at the onset and in the aftermath of OAE 1a, slightly pre-or postdating the deposition of dark organic-rich black shales in pelagic basins. This study presents evidence for a punctuated and well-expressed early Aptian bloom of the ulvophycean green algae Lithocodium aggregatum observed at the proto-North Atlantic margin, Lusitanian Basin, Portugal. Similar to southern and central Tethyan sections, a Lithocodium-dominated interval temporally replaces the rudist-dominated platform ecosystem. This Lithocodium-rich horizon is composed of oncoidal fl oatstones and boundstones, including a well-exposed biohermal level, and reaches a thickness of up to 6 m. High-resolution carbon-isotope stratigraphy shown here clearly argues for Lithocodium to represent a biotic harbinger of environmental change in the run-up of OAE 1a. Chemo stratig raphy provides evidence that the subsequent carbonate platform breakdown in the proto-North Atlantic was coeval with an early Aptian carbonate platform drowning episode observed in the north-ern Tethys prior to OAE 1a. A regionally enhanced nutrient level and a relative sealevel rise are suggested to have triggered the transient mass occurrence of Lithocodium microencrusters, which also may have been infl uenced by elevated atmospheric CO 2 concentrations related to the emplacement of the Ontong Java large igneous province. Upwelling water masses and enhanced terrigenous runoff due to increased weathering may have served as possible sources of the required nutrients, which tentatively diminished and fi nally interrupted the metazoan carbonate platform factory.

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Calcareous nannofossil biostratigraphy of an outcrop section of Aptian sediments of west-central Portugal (Lusitanian Basin)

Cited by 8 publications

References 15 publications

Is Strontium-isotope stratigraphy a reliable tool for dating shallow-marine platform carbonates at the Barremian-Aptian transition? Review of western Tethyan case studies

Is Strontium-isotope stratigraphy a reliable tool for dating shallow-marine platform carbonates at the Barremian-Aptian transition? Review of western Tethyan case studies

Evaluating the role of coastal hypoxia on the transient expansion of microencruster intervals during the early Aptian

Early Aptian algal bloom in a neritic proto-North Atlantic setting: Harbinger of global change related to OAE 1a?

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