Geochemistry and chemostratigraphy of the Colón-Mito Juan units (Campanian-Maastrichtian), Venezuela: Implications for provenance, depositional conditions, and stratigraphic subdivision

Montilla, Linda; Martínez, M.; Márquez, G.; Escobar, Marcos; Sierra, Carlos; Gallego, J.R.; Estéves, Ivan; Gutiérrez, José

doi:10.2343/geochemj.2.0275

Cited by 5 publications

(3 citation statements)

References 38 publications

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“…Although the authors did not perform any paleoenvironmental inferences, it is known that the Colón Formation (hereafter Fm) was deposited in a shallow marine environment, whereas the Mito Juan Fm was deposited under deltaic conditions (Fig. 12) (Montilla et al, 2013). This is compatible with the high abundance of Nypa pollen, which probably originated in coastal environments dominated by this palm.…”

Section: Tablementioning

confidence: 91%

The Caribbean Mangroves: an Eocene innovation with no Cretaceous precursors

Rull¹

2022

Preprint

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The mangrove communities of the Caribbean region are considered descendants of former pantropical Late-Cretaceous mangroves that underwent regional differentiation after the tectonic closure of the Tethys Sea. The southern Caribbean area has been considered the cradle of Neotropical mangroves. These inferences were based mainly on qualitative evidence, such as the presence/absence of fossils showing botanical affinities with present-day mangrove taxa. However, as demonstrated in Quaternary paleoecology, the most suitable approach for reconstructing past plant communities is the assemblage approach, which is based on quantitative palynology. Therefore, the problem of the origin of Caribbean mangroves, as ecological communities, is addressed here by reviewing in detail the Late Cretaceous to Eocene quantitative palynological studies available for the region to properly reconstruct past mangrove assemblages. No evidence has been found for the occurrence of mangrove ecosystems during the Late Cretaceous and the Paleocene, only records of the fossil representatives of some individual taxa (Nypa, Acrostichum), which are not mangrove-forming elements and, hence, are not reliable indicators of mangrove communities. The first robust evidence of true mangrove communities was found in the Middle Eocene (Lutetian). These mangrove communities were dominated by the fossil representative of Pelliciera, a mangrove-forming tree with a Neotropical distribution by that time. Back-mangrove communities were dominated by the palm Nypa (which was pantropical by that time but is now restricted to the Indo-Mayana region), the fern Acrostichum and palms, notably Mauritia, along a sea-land saline to freshwater community gradient. Pelliciera originated in the southern Caribbean during the Early Eocene and became dominant in the Middle Eocene, when it dispersed across the Caribbean area, probably favored by the migration of the Caribbean plate. Therefore, the first Caribbean mangroves were ecological and evolutionary innovations that emerged de novo during the Middle Eocene, rather than a consequence of the regional evolutionary differentiation from hypothetical Late-Cretaceous Tehtyan mangroves, whose existence is not supported by quantitative palynological records. It is proposed to develop this type of study for other tropical/subtropical mangrove communities, for a sounder view of mangrove origin and evolution, at a global scale.

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Section: Tablementioning

confidence: 91%

The Caribbean Mangroves: an Eocene innovation with no Cretaceous precursors

Rull¹

2022

Preprint

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“…In a geochemical perspective, the composition of fine-grained sedimentary rocks usually come from detrital, authigenic, redox, bioproductivity, etc., which can be identified by the PCA [42,43]. In this sense, we think the data reduction process of the chemostratigraphic dataset is the same process for the identification of chemofacies by PCA [44,45].…”

Section: Principal Component Analysismentioning

confidence: 94%

Chemostratigraphic Analysis of Wufeng and Longmaxi Formation in Changning, Sichuan, China: Achieved by Principal Component and Constrained Clustering Analysis

et al. 2021

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The increasing proportion of unconventional worldwide energy demands have consistently promoted the necessity for exploring a precise, high-resolution, objective, and quantitative stratigraphic division method for macroscopically homogeneous mudstone successions. The chemostratigraphy can resolve this problem well, although it has been applied successfully in North America, but not systematically studied in China for shale gas exploration and development. This work has conducted a chemostratigraphic analysis of Wufeng and Longmaxi Formation on the Changning section of Sichuan Province, southwestern China, to testify its applicability for shale gas exploration in China. Principal component analysis (PCA) was first employed to reduce the dimensionality of datasets. Three chemofacies, including detrital (K, Ti, Fe, Al, Na, Mg, Cr, Zr, Rb), authigenic (Ca, Sr, Mn, Si, S, Ba), and redox-organic (P, V, Ni, Zn, Cu, TOC), were found. Subsequently, constrained clustering analysis was utilized for the zonation of each chemofacies into chemozones. Consequently, the whole Changning section was divided into twelve chemozones (CZ I–CZ Ⅻ). The geochemical interpretation for these chemozones can be resolved from the regional changes in paleogeography and paleoceanography during the Late Ordovician to Early Silurian period. Thus, a three-stage geochemical evolution along the Changning section can be classified: (1) the siliceous and anoxic deposits of Wufeng Formation (CZ I–CZ III) with high TOC contents; (2) the siliceous and anoxic sedimentary rocks of bottom Longmaxi Formation with still higher TOC (CZ Ⅳ); (3) the calcarous-detrital and oxic sediments for the rest of Longmaxi Formation (CZ Ⅴ–CZ Ⅻ). In considering their high content of TOC and abundant brittle siliceous minerals, the CZ (I–Ⅳ, 0 m–33.6 m) are thought to be the most preferable sweet spot for shale gas exploration.

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“…Ezzel együtt más kutatók a lepusztulási terület kőzettani felépítését az üledékes kőzetek geokémiai vizsgálatával is megpróbálják azo nosítani (pl. PRESTON et al 1998, PEARCE et al 1999, ANDERSSON et al 2004, SABAOU et al 2009, MONTILLA et al 2013, WRAY & JEANS 2014. Egyes szerzők például bizonyos kémiai elemek teljes kőzetben mért mennyiségéből, azok arányaiból, valamint a jellemző izotóparányokból következtettek a lepusztulási terület összetételére és jellegére (pl.…”

Section: Bevezetésunclassified

Törmelékes rétegsorok komplex eredetvizsgálata (KEVi). Ötelemes, összehangolt törmelékeskőzet-elemző vizsgálatsor

2018

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It is well known that clastic rocks have great economical and scientific importance as for example may represent hydrocarbon-and water reservoires and remnants of totally eroded mountain belts. The precise mineralogicalpetrological determination (petrography) of their detrital grains and identification of their source area are important research direction for both areas. Traditionally, two main trends have been developed for the provenance examination of unconsolidated clastic sequences: Pebble petrography, which performs the macroscopic determination and thin-section examination of the individual pebbles larger than a few centimetres and the heavy mineral analyses, which targets the sand fraction. Both methods have serious deficiencies. To eliminate some of these deficiencies, the fine-grained pebble examination (FPE) method has been introduced into the petrographic examinations in the last few years. However it has not resolved the problem to unequivocally link different heavy minerals to source rock types. The aim of this paper is to present a grain determination procedure that allows to identify the source rock types of clastic deposites with improved accuracy, by reducing the uncertainity that would arise from using one or the other method separately. Our approach -the Expanded Provenance Analysis (EPAn) -is a combined procedure of five different grain/clast determination methods. These include both, previously utilised techniques and one that is proposed herein for the first time. This paper describes and evaluates the EPAn approach. ÖsszefoglalásKözismert, hogy a törmelékes kőzetek, mint például szénhidrogén-, vagy víztároló képződmények, és mint eltűnt hegységek lepusztulási maradékai komoly gazdasági és tudományos jelentőséggel bírnak. Törmelékszemcséinek pontos ásvány-kőzettani és geokémiai és forrásterületük azonosítása mindkét terület számára fontos kutatási irányt jelenthet. Laza törmelékes rétegsorok forrásterület-vizsgálatára hagyományosan két fő irányzat alakult ki: a nagyobb méretű kavicsok petrográfiája, amellyel az egyedi, néhány cm-nél nagyobb méretű kavicsok makroszkópos, terepi és vékonycsiszolatos vizsgálatát végezzük, valamint a nehézásvány vizsgálat, amely a rétegek homokméretű ásványszemcséinek meghatározásával foglalkozik. Mindkét módszernek komoly hiányosságai vannak. Ezek egy részének kiküszöbölésére az utóbbi években bevezették a beágyazott szemcsecsiszolatos vizsgálati módszert, de a nehézásványok biztos kőzethez rendelhetősége így sem oldódott meg. Ezzel a munkánkkal az a célunk, hogy egy olyan vizsgálatsort mutassunk be, amely laza üledékes rétegsoroknak az eddigieknél sokkal pontosabb és biztosabb forrás meghatározását teszi lehetővé, és amelynek segítségével kiküszöbölhetők a korábban alkalmazott módszerek egyedi hiányosságai. Az általunk komplex eredetvizsgálatnak (KEVi) nevezett módszer olyan ötelemes szemcseelemző vizsgálatsor, amely az eddig hagyományosan és újabban használt, valamint ebben a cikkben használt újonnan bemutatott vizsgálatokat együttesen, összehangoltan tartal...

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Geochemistry and chemostratigraphy of the Colón-Mito Juan units (Campanian-Maastrichtian), Venezuela: Implications for provenance, depositional conditions, and stratigraphic subdivision

Cited by 5 publications

References 38 publications

The Caribbean Mangroves: an Eocene innovation with no Cretaceous precursors

The Caribbean Mangroves: an Eocene innovation with no Cretaceous precursors

Chemostratigraphic Analysis of Wufeng and Longmaxi Formation in Changning, Sichuan, China: Achieved by Principal Component and Constrained Clustering Analysis

Törmelékes rétegsorok komplex eredetvizsgálata (KEVi). Ötelemes, összehangolt törmelékeskőzet-elemző vizsgálatsor

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