Stratigraphy, microfossils and depositional environments of the lowermost part of the Welton Chalk Formation (late Cenomanian to early Turonian, Cretaceous) in eastern England

Dodsworth, Paul

doi:10.1144/pygs.51.1.45

Cited by 25 publications

(8 citation statements)

References 81 publications

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“…Subsequent treatment with an alkali solution was necessary to remove post-oxidation waste products. Previous work on CenomanianÀTuronian organic-rich shales has indicated that excessive post-HF treatment led to selective destruction of non-peridinioid dinoflagellate cysts (Dodsworth 1995(Dodsworth , 1996(Dodsworth , 2004a. Experiments with Eagle Ford Group post-HF residues indicated that 'optimum oxidation' was achieved with extended maceration in cold or warm nitric acid, Schulze's Solution (warmed 70% nitric acid supersaturated with potassium chlorate) and/or fuming nitric acid, followed by a single rinse in a detergent that contained a trace of ammonia.…”

Section: Methodsmentioning

confidence: 99%

“…The isolated influx at Lozier Canyon is stratigraphically lower and therefore older than the astronomical age calibration (92.87 Ma; Figure 2) for top frequent C. compactum-membraniphorum in Iona-1. (Dodsworth 1996(Dodsworth , 2000, northern Germany (Marshall & Batten 1988), southern France (cf. Courtinat et al 1991;Jarvis et al 2011) and at a comparable stratigraphical level in northern France (Foucher 1983) and Crimea (Dodsworth 2004a).…”

Section: Top Common Cyclonephelium Longispinatummentioning

confidence: 99%

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Palynostratigraphy and palaeoenvironments of the Eagle Ford Group (Upper Cretaceous) at the Lozier Canyon outcrop reference section, west Texas, USA

Dodsworth¹

2015

Palynology

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This study describes the detailed palynology of the Eagle Ford Group at Lozier Canyon, its principal outcrop reference section in west Texas. Prominent marine phytoplankton assemblages are consistent with a proposed depositional setting for Lozier Canyon on a submarine platform within the Cretaceous Western Interior Seaway (KWIS) of the USA. The Lower Eagle Ford Formation (middle to upper Cenomanian) was deposited under restricted marine conditions with oxygen-deficient, probably anoxic bottom waters, as indicated by the black, organic-rich (ca. 1 to > 6% total organic carbon) shale lithology. The formation comprises two fourth-order stratigraphical sequences, each showing sedimentary evidence of increasing water depth during deposition. Palynomorph assemblages from the sequences are dominated by green algal prasinophyte phycomata in the lower parts and peridinioid dinoflagellate cysts in the upper parts. The productivity of these marine phytoplankton groups may have been stimulated by availability of ammonium (prasinophytes) and nitrite (peridinioids) from upwelling, or vertical expansion of the oxygen-minimum zone. The transition from prasinophyte-to peridinioid-dominated assemblages may reflect elevation of the photic zone to a level less regularly encroached by deeper, ammonium-enriched waters of the denitrification zone. The overlying Upper Eagle Ford Formation (upper Cenomanian to upper Turonian or Coniacian) was deposited under deeper, relatively open marine conditions, as indicated by a decrease in organic carbon content and an increase in carbonate content. This is supported by the presence of diversified dinoflagellate cyst assemblages, including inter-regional (high-to mid-latitude) marker events; in the upper Cenomanian, base and acme Cyclonephelium compactum-membraniphorum, top consistent and frequent Litosphaeridium siphoniphorum, and top Adnatosphaeridium tutulosum; in the middle to upper Turonian, range bases of Heterosphaeridium difficile and Senoniasphaera rotundata. The stratigraphical resolution offered by palynology indicates potential application to wellsite 'geosteering' of commercial shale oil and shale gas wells drilled in the Eagle Ford Group.

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Section: Methodsmentioning

confidence: 99%

Section: Top Common Cyclonephelium Longispinatummentioning

confidence: 99%

Palynostratigraphy and palaeoenvironments of the Eagle Ford Group (Upper Cretaceous) at the Lozier Canyon outcrop reference section, west Texas, USA

Dodsworth¹

2015

Palynology

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“…Palynological data from Melton Ross (Dodsworth, in prep transgression could also be invoked to account for the increase in terrigenous clays and palynomorphs at this level. It is noteworthy that abundant C. cornpactum -C. membraniphorum complex has also been reported from the uppermost Cenomanian -lowermost Turonian 'black shales' in northern Germany (Marshall & Batten, 1988) and eastern England (Duane, in Hart et al, 1991Dodsworth, 1996), as shown in Figure 12. This may signify an extra-basinal influence, possibly the widespread expansion and intensification of oxygen-minimum zones (Schlanger & Jenkyns, 1976), associated with the anomalous palaeoenvironmental conditions of the Cenomanian-Turonian boundary mass extinction interval/'oceanic anoxic event'.…”

Section: Distribution Of Palynomorphs At Pueblomentioning

confidence: 84%

“…Reworking of mud to the basin (e.g., Jenkyns, 1980) and/or the formation of swamps due to drowning of land masses (cf., Ioannides et al, 1977) during Jefferies (1963) and Gale (1996); 4. Beds A-H of Dodsworth (1996), triple-lines indicate probable hiatuses in this condensed section; 5. Palynological data from Melton Ross (Dodsworth, in prep transgression could also be invoked to account for the increase in terrigenous clays and palynomorphs at this level.…”

Section: Distribution Of Palynomorphs At Pueblomentioning

confidence: 91%

Trans-Atlantic dinoflagellate cyst stratigraphy across the Cenomanian–Turonian (Cretaceous) Stage boundary

Dodsworth

2000

J. Micropalaeontol.

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Abstract. The principal palynological proxy for the Cenomanian–Turonian Stage boundary, the top of consistent/common Litosphaeridium siphoniphorum (a dinoflagellate cyst), occurs in Greenhorn Bed 73 at the international stratotype section, west of Pueblo, Colorado, USA. This datum occurs in the same position, as indicated by planktonic foraminifera (a few beds higher than the range top of R. cushmani), ammonites (upper part of the S. gracile/M. geslinianum Zone) and geochemistry (immediately below maximum δ13C values), at Pueblo (Western Interior Basin) and localities in southern England (Wessex–Paris Basin) and northern Germany (Lower Saxony Basin). Of over 100 dinoflagellate cyst taxa recorded from Pueblo and a correlative section at Lulworth, southern England, possibly as few as six do not range into the Turonian. In the uppermost Cenomanian – lowermost Turonian succession at Pueblo, there are no consistent absences of any common taxa (with four exceptions) and there is no evidence for a collapse in cyst-forming dinoflagellate populations during the Cenomanian–Turonian boundary mass extinction interval/‘oceanic anoxic event’. However, the composition of palynological assemblages from the Upper Cenomanian appears to reflect palaeoenvironmental stress and/or an increase in the supply of land-derived and relatively nearshore palynomorphs.

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“…Subsequent treatment with an alkali solution was necessary to remove postoxidation waste products. Previous work on C-torganic-rich shales has indicated that excessive post-HF treatment led to selective destruction of gonyaulacacean and areoligeracean dinocysts (Dodsworth, 1995(Dodsworth, , 1996(Dodsworth, , 2004. Experiments with Eagle Ford post-HF residues indicated that "optimum oxidation" was achieved with extended maceration in cold nitric acid (HNO 3 ).…”

Section: Palynological Methodsmentioning

confidence: 99%

An astronomically calibrated stratigraphy of the Cenomanian, Turonian and earliest Coniacian from the Cretaceous Western Interior Seaway, USA: Implications for global chronostratigraphy

Eldrett

Bergman

et al. 2015

Cretaceous Research

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141

154

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Stratigraphy, microfossils and depositional environments of the lowermost part of the Welton Chalk Formation (late Cenomanian to early Turonian, Cretaceous) in eastern England

Cited by 25 publications

References 81 publications

Palynostratigraphy and palaeoenvironments of the Eagle Ford Group (Upper Cretaceous) at the Lozier Canyon outcrop reference section, west Texas, USA

Palynostratigraphy and palaeoenvironments of the Eagle Ford Group (Upper Cretaceous) at the Lozier Canyon outcrop reference section, west Texas, USA

Trans-Atlantic dinoflagellate cyst stratigraphy across the Cenomanian–Turonian (Cretaceous) Stage boundary

An astronomically calibrated stratigraphy of the Cenomanian, Turonian and earliest Coniacian from the Cretaceous Western Interior Seaway, USA: Implications for global chronostratigraphy

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