Optimum microfossil sequences and cyclic sediment patterns in Early Cretaceous pelagic strata

Three sequencing methods were used to calculate the most likely biozonation and the periodicity of sedimentary cycles in Lower Cretaceous pelagic strata of the Atlantic and Indian oceans.A database was built of 378 first and last stratigraphic occurrences of calcareous nannofossils, dinocysts, foraminifers, and geomagnetic reversals in highest Jurassic through Lower Cretaceous deep marine strata at 10 Atlantic Ocean and 3 Indian Ocean drilling sites. There are 135 different events in total, about one third of which are unique to either ocean. Using the complete data set, the quantitative stratigraphy methods STRATCOR and RASC calculated closely comparable optimum sequences of average first- and last-occurrence positions. The preferred zonal solution, based on the STRATCOR method, includes 56 events, each of which occurs at three or more sites. The events comprise 6 geomagnetic reversals, 25 nannofossils, 5 planktonic foraminifera, 8 benthic foraminifera, and 12 dinocysts occurrences. Nine assemblage zones have been recognized of Tithonian through Albian age. All but 2 of 18 nannofossil events in the Atlantic Ocean optimum sequence were reported in the same stratigraphic order in a standard Mesozoic nannofossil zonation.Our quantitative examination, using Walsh spectral analysis, of the Lower Cretaceous cyclic sequences at three Deep Sea Drilling Project (DSDP) sites in the Atlantic Ocean generally supports the hypothesis that they are the product of cyclic climatic changes controlled by the Milankovitch orbital cycles. The peaks in the power spectra usually can be related to obliquity and precession cycles; some peaks seem to correspond to the eccentricity cycle. Obliquity seems to be the most important and persistent orbital element responsible for cyclic sedimentation in the Early Cretaceous Atlantic Ocean.The actual pelagic sedimentation rates were calculated for some cores using the results of spectral analysis. The correlation of the actual pelagic sedimentation rate with cyclic patterns and the occurrence of calcareous turbidites indicate that the changes in cycle pattern are the reflection of changes in the oceanographic setting. The changes in oceanographic setting are related to relative-sea-level fluctuations. The intervals dominated by laminated limestone were deposited during higher sea-level periods.

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SIDERITE AS A CONSTRAINT ON DEPOSITIONAL AND EARLY DIAGENETIC HISTORY: EXAMPLES FROM BARROW SUB-BASIN, NORTH WEST SHELF, WESTERN AUSTRALIA

The APPEA Journal ◽

10.1071/aj97012 ◽

1998 ◽

Vol 38 (1) ◽

pp. 238 ◽

Cited By ~ 1

Author(s):

G. M. Kraishan ◽

N. M Lemont

Keyword(s):

Sea Level ◽

Early Cretaceous ◽

Meteoric Water ◽

Sea Water ◽

Depositional Environments ◽

Late Triassic ◽

Pore Waters ◽

Sea Level Fluctuations ◽

Isotopic Studies ◽

Mn Content

Siderite cement is one of the most volumetrically important diagenetic minerals in the Late Triassic to Early Cretaceous sandstones of the Barrow Sub-basin. It constitutes up to 60 per cent of the rock volume, and where abundant, occludes the primary intergranular porosity. Petrogriiphic, chemical and isotopic studies indicate the early precipitation of much of this siderite prior to significant compaction. Siderite samples and concretions were taken from a variety of depositional environments ranging from fluvial to deep marine from Late Triassic to Early Cretaceous sequences.Of the early phases, three distinct siderite types were recognised and vary according to depositional environment. The first type, mostly collected from fluvial deposits, is Fe-rich with a mean composition of (Fe96.3 Mg1.8 Ca0.9 Mn1.0) C03. The second type of siderite cement is relatively Mg-rich, Ca-poor and has a higher Mn content, with a mean composition of (Fe87.1 Mg9.6 Ca1.2 Mn2.1) C03. The third type of siderite cement is typically Mg−, Ca-rich, with a low Mn content and an average composition of (Fe78.7 Mg12.4 Ca8.4 Mn0.5) C03. The second and third siderite cements occur in marine facies. The δ13C and δ180 values for siderite cements range from −2.8 to −14.3 %. PDB and 17.4 to 28.2 %. SMOW, respectively.Petrographic and chemical isotopic studies and other sedimentological data from siderite can be used to distinguish between different depositional environments. Chemical and isotopic compositions of the early authigenic siderites indicate precipitation from fluids with significant meteoric input. Siderite cements formed during sulphate reduction and early methanogenesis from mixed marine and meteoric pore-waters at temperatures below 30°C. While an influx of meteoric water to the fluvial and deltaic sediments of the Triassic Mungaroo Formation is easily envisaged, the siderites show that some mixing of sea water is also required. The concept of introduction of meteoric water to the marine sediments of the Birdrong Formation requires an appreciation of the sea level fluctuations at the time. In these situations, the recognition of meteoric or marine input to an early siderite cement can assist in the determination of sea level fluctuations.

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Tectonic and Eustatic Sea-Level Fluctuations During the Early Cretaceous: A Case Study from the Berriasian–Valanginian Sequences in Saudi Arabia

The Structural Geology Contribution to the Africa-Eurasia Geology: Basement and Reservoir Structure, Ore Mineralisation and Tectonic Modelling - Advances in Science, Technology & Innovation ◽

10.1007/978-3-030-01455-1_69 ◽

2018 ◽

pp. 315-317

Author(s):

Abdullah O. Bamousa

Keyword(s):

Saudi Arabia ◽

Sea Level ◽

Early Cretaceous ◽

Sea Level Fluctuations

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A multi-proxy record of the Latest Danian Event at Gebel Qreiya, Eastern Desert, Egypt

Journal of Micropalaeontology ◽

10.1144/0262-821x10-023 ◽

2011 ◽

Vol 30 (2) ◽

pp. 167-182 ◽

Cited By ~ 29

Author(s):

J. Sprong ◽

M. A. Youssef ◽

A. Bornemann ◽

P. Schulte ◽

E. Steurbaut ◽

...

Keyword(s):

Sea Level ◽

Benthic Foraminifera ◽

Environmental Changes ◽

Eastern Desert ◽

Trace Element Geochemistry ◽

Calcareous Nannofossils ◽

Element Geochemistry ◽

Sea Level Fluctuations ◽

Sequence Of Events ◽

Carbon Isotope Excursion

Abstract. The Latest Danian Event (LDE) is a proposed early Palaeogene transient warming event similar to the Paleocene–Eocene Thermal Maximum, albeit of smaller magnitude. The LDE can be correlated with a carbon isotope excursion (‘CIE-DS1’) at Zumaia, Spain, and the ‘top Chron C27n event’ defined recently from ocean drilling sites in the Atlantic and Pacific, supporting a global extent. Yet, records of environmental change during the LDE (e.g. warming and sea-level fluctuations) are still rare. In this study, we focus on the micropalaeontology (calcareous nannofossils and benthic foraminifera), mineralogy and trace element geochemistry of the LDE in the Qreiya 3 section from the southern Tethyan margin in Egypt. In this section, the LDE is characterized by the occurrence of anomalous beds intercalated within upper Danian shales and marls. The event beds of the LDE are situated above an unconformity on top of a shallowing-upwards sequence deposited in a well-oxygenated outer neritic to upper bathyal marine palaeoenvironment. The lower LDE bed is barren of benthic foraminifera, but contains pyrite and fish remains, and is interpreted as an anoxic level formed during rapid relative sea-level rise. Incursion of a Neoeponides duwi (Nakkady, 1950) benthic assemblage in LDE bed II is interpreted as repopulation of the seafloor after anoxia. The sea-level cycle associated with the LDE is estimated at about 50 m maximum in the Qreiya 3 section. The environmental changes at Qreiya 3 are of supra-regional extent, since a similar sequence of events has been observed at other southern Tethyan locations.

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Relationship between sequence boundaries and the evolutionary history of planktonic foraminifera, calcareous nannofossils, and reef communities in the mid-Cretaceous (Barremian-Cenomanian)

The Paleontological Society Special Publications ◽

10.1017/s2475262200007395 ◽

1992 ◽

Vol 6 ◽

pp. 179-179 ◽

Cited By ~ 1

Author(s):

R. Mark Leckie ◽

Robert W. Scott ◽

Timothy J. Bralower ◽

William V. Sliter

Keyword(s):

Sea Level ◽

Planktonic Foraminifera ◽

Marine Biota ◽

Calcareous Nannofossils ◽

Reef Communities ◽

Anoxic Events ◽

History Of ◽

Calcareous Plankton ◽

Sequence Boundaries ◽

Major Sequence

Planktonic foraminifera first evolved in the middle Jurassic but did not experience a major radiation until the mid-Cretaceous. The mid-Barremian to late Aptian was characterized by a steady increase in species richness and by the appearance of new morphological forms including planispiral coiling, clavate and radially elongate chambers, and culminating in the first appearance of taxa with complex apertural structures and the keeled morphotype in late Aptian time. This broad interval of radiation was abruptly ended by evolutionary turnover and low diversification rates in the latest Aptian and early Albian prior to a second explosive episode of radiation in the middle and late Albian. The evolutionary history of mid-Cretaceous calcareous nannofossils generally parallels the trends observed in planktonic foraminifera, although the latest Aptian-early Albian turnover event is not as pronounced. Reef communities in the Caribbean/Gulf of Mexico and Mediterranean provinces show a change in dominance from coral-algal-rudist reefs in the Barremian-early Albian to rudist domiance by the late Albian time. These changes in calcareous plankton and reef communities are related to complex oceanographic changes of the mid-Cretaceous including structure of the upper water column, productivity, sea level, atmospheric and oceanographic circulation, and changes in the chemistry of the ocean.Changes in eustatic sea level influenced many of these factors including nutrient delivery to the oceans, climate, sites and rates of deep water formation, and ocean chemistry. What is the relationship between changes in sea level, as expressed by major seismic sequence boundaries, and the changes observed in marine biota? We have compared major changes of eustatic sea level within this interval of generally rising global sea level (Scott et al., 1988), with equivalent sequence boundaries (Haq et al., 1988) and the records of calcareous plankton (Roth, 1987; Leckie, 1989) and reef communities (Scott, 1988). What is most striking about these relationships is the apparent lack of direct correlation between sequence boundaries and turnover events in the marine biota. The calcareous plankton alternate in phase between relatively high rates of diversification and low rates of diversification, with the major sequence boundaries falling within intervals of change rather than at intervals of change. However, we acknowledge the potential of missing or condensed intervals in deep sea settings which may influence the record of evolutionary rates (e.g., Loutit, et al., 1988). Only the basal Albian sequence boundary appears to correlate with a major turnover event in the planktonic foraminifera, and the rapid change in Gulf Coast reef communites between the middle and upper Albian may correlate with a eustatic sea level change and a major sequence boundary. Based on high-resolution calcareous nannofossil, planktonic foraminiferal, sedimentologic, and geochemical data of Bralower et al. (submitted), the lower Aptian, basal Albian, and lower upper Albian sequence boundaries appear to correlate more closely with widespread oceanic dysoxic/anoxic events OAE1a, OAE1b, and OAE1c, respectively. The correlations between evolutionary events, anoxic events, and sequence boundaries must be considered tentative at this time because major disparities exist between the correlation of calcareous plankton zones and mid-Cretaceous chronostratigraphic units used by Haq et al. (1988) and Bralower et al. (submitted).

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