LABCRET

LABRADOR SHELF: CRETACEOUS STRATIGRAPHY OF 14 WELLS

LABRADOR SEA [2]Click on the arrows below for an outline and contents of the study.

Please contact Dr Jonathan Bujak for further details.

BACKGROUND

BACKGROUND

The study was undertaken jointly by Bujak Research and David Mudge Associates on the Cretaceous and Lower Palaeocene stratigraphy and hydrocarbon plays in 14 wells located on the Labrador Shelf and West Greenland. This provides data and interpretations on the Mesozoic of the region, complementing the Bujak Mudge NWAM study on the overlying Palaeocene-Eocene section.

OUTLINE OF THE STUDY

OUTLINE OF THE STUDY

Interpreted well log and biostratigraphic data from 14 wells are used to develop a sequence stratigraphic scheme that can be applied to all the Labrador wells, and can also be used to correlate with the Cretaceous succession in the Grand Banks and Scotian Shelf areas.

The biostratigraphic analysis involved the quantitative palynology of 799 ditch cuttings and 96 sidewall core samples, and micropaleontology of 429 ditch cuttings and 35 sidewall core samples from the pre-Cretaceous, Cretaceous and Lower Palaeocene intervals. These data are integrated with the well gamma, sonic and resistivity curves and lithological interpretation to produce a digital stratigraphic log for each well. The first sheet displays stratigraphic surfaces and sequences, rock units, lithology and bioevents plotted against wireline log curves. On the second sheet, sawtooth distributions illustrate the changes in microfossil assemblages through the Cretaceous interval and a plot of depositional facies provides an interpretation of paleoenvironmental and water depth changes. An accompanying spreadsheet gives the depths of the bioevents and stratigraphic surfaces.

The six stratigraphic sequences defined in the study are bounded by a series of surfaces that record uplift events in the Labrador-Greenland region. Each sequence contains a distinctive set of lithofacies and biofacies representing a predictable succession of depositional environments that developed across the Labrador Shelf during the Cretaceous. The uplift events, which form base Cretaceous or intra-Cretaceous unconformities in many Labrador Shelf wells result from both tectonic (rift-related) and epeirogenic (transient thermal uplift) mechanisms in the crust and upper mantle. Biostratigraphic analysis shows that many of the uplift surfaces are important regional stratigraphic events associated with missing section and significant changes in microfossil assemblages and depositional environments.

The stratigraphic sequences are tied to a biostratigraphic zonation, DK1 to DK12, based on dinocysts. This alpha-numeric scheme can be correlated directly with the palynological scheme erected for the Scotian Shelf and Grand Banks areas by Bujak & Williams (1978).

The dinocysts and non-marine miospores can also be correlated with assemblages from the Arctic, thereby providing a chronostratigraphic tie for Cretaceous geological events around the offshore eastern Canada seaboard from the Scotian Shelf northwards to the Beaufort Sea and Mackenzie Delta.

REFERENCES

BUJAK, J.P. & WILLIAMS, G.L. 1978. Cretaceous palynostratigraphy of offshore southeastern Canada. Geological Survey of Canada, Bulletin 297.

CONTENTS

TEXT

  1. Introduction
  1. Stratigraphic framework

2.1       Biostratigraphic framework

2.2       Stratigraphic surfaces

2.3       Stratigraphic sequences and depositional environments

  1. Biostratigraphic analysis
  1. References

Appendix: Interpreted stratigraphic logs and spreadsheet data

FIGURES

Figure 1.Labrador Shelf well location map

Figure 2. Cretaceous stratigraphic table

Figure 3. Cretaceous well correlation

Figure 4. Cretaceous unconformities and missing section

Figure 5. Cretaceous depositional environments

TABLES

Table 1. Microfossil bioevents, Cretaceous to Danian, Labrador Shelf

WELL LISTING

Bjarni H-81

Bjarni O-82

Freydis B-87

Gilbert F-53

Gudrid H-55

Herjolf M-92

Hopedale E-33

North Bjarni F-06

North Leif I-05

Ogmund E-73

Roberval K-92

Skolp E-07

Snorri J-90

Tyrk P-100


EXAMPLE FIGURES

LABCRET Figure 1 Figure 1. Labrador Shelf well location map

 

 

 

 

LABCRET Figure 3 Figure 3. Cretaceous well correlation

 

 

 

 

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