pet eng field guide 2014

University of Manchester Petroleum Geoscience MSc

Northeast England Field Trip

University of Manchester School of Earth, Atmospheric and Environmental Sciences

Manchester M13 9PL

Petroleum Geoscience MSc

2

CONTENTS 1.0 INTRODUCTION

1.1 Hotel Details, Emergency Contact Numbers and Class List 1.2 Location Maps 1.3 Safety in the Field 1.4 Field Course Aims

1.5 Structural Setting 1.6 Stratigraphy 1.7 Regional Setting 1.8 Selected References

2.0 STAITHES

3.0 WHITBY

4.0 FLAMBOROUGH HEAD


3

1.1 Hotel Details, Emergency Contact and Class List

The Royal Hotel: Scarborough, St Nicholas Street, Scarborough, North Yorkshire, UK YO11 2HE TEL : 01723 364 333

Emergency Contact: In an emergency contact with the party can be made through the School office: +44 (0)161 306 6871

1.2 Maps and location

The following maps cover the coastal sections visited on this course. 1. OS 1:50 000. Sheet 93: Middlesborough Sheet 94: Whitby Sheet 101: Scarborough and Bridlington.

12/ 10/ 2011 12:26Royal Hotel, St. Nicholas Street, Scarborough, UK - Google Maps

Page 1 of 1http:/ / maps.google.com/ maps?f= q&source= s_q&hl= en&geocode= &q= 0.007504,0.021865&t= m&z= 16&ei= EnmVTu- 5MMjj8QPu9IixAw&pw= 2

Royal Hotel, St. Nicholas Street,Scarborough, UK

A. Royal HotelSt. Nicholas Street, Scarborough, NorthYorkshire YO11 2HE, United Kingdom+44 1723 356771 !

10 reviews

Prices converted at current exchange - Disclaimer

2011 Google -

Figure 1.1 Hotel location


4

1.3 Safety in the field.

Before examining any locality, determine the risks and take appropriate care. Be aware not only of your own safety, but also of those with you. A safety briefing will be held at the start of each day, and at each locality. At all times participants must follow the instructions of the field trip leaders. All participants will be required to complete a safety form and detail any medical conditions At all times field trip participants must wear hard hats when near to cliffs, appropriate footwear (walking boots) and if required high-visibility jackets. If you wish to hit a rock with a hammer you must wear safety goggles. You must neither stand under any overhangs, nor bring down debris on to field trip participants below. The rocks on the coastline are very slippery - please take extreme care. Please be aware of the tide warnings at each locality. In poor weather participants should have waterproof clothing and be prepared for cold conditions (windy) on the coast.

1.4 Field work location, aims and assessment

We will examine Jurassic and Cretaceous sediments that outcrop along the Yorkshire coast. The aims of the field course is to illustrate the main elements of a hydrocarbon system and develop skills in sedimentology and stratigraphy using selected exposures of different rock types ranging from Lower and Middle Jurassic age. The fieldwork will involve the examination of sediments deposited in a range of depositional environments from fluvial to coastal plain and marine outer shelf. The sediments will be examined in terms of their lithological characteristics in order to define the facies present. An environmental interpretation will be based on the facies, sedimentary structures and fossils they contain. We will also introduce the basic concepts of sequence stratigraphy. The sections will then be assessed in terms of the petroleum system, to determine the potential for reservoir, source, seal, trap and migration. There are three main localities to be visited to examine, three Middle Jurassic strata stratigraphic intervals

1. Staithes: Middle Jurassic shoreface to offshore transition mudstones (Toarcian)

2. Whitby Harbour: fluvial sandbody geometry (Aalenian) and outer shelf

(Toarcian).

3. Flamborough Head: Cretaceous chalk


5

Figure 1.2 Summary geological maps of Yorkshire coast

Periods Age Ma Stages Formation

Upper Santonian Burnham Chalk

Cretaceous 66 Middle Lower

Upper

Jurassic

144

Middle

Bajocian

Aalenian

Scarborough Cloughton

Saltwick

Lower

Toarcian

Pleinsbachian

Dogger Whitby Mudstone

Cleveland Ironstone Staithes Sandstone

Fig. 1.3 Summary stratigraphy of field area 1.5 Geological Setting


6

We will examine the JurassicThe last stages of the Variscan orogeny produced a mountain range which spread from north-west Spain, through Brittany and Central Germany to Poland and beyond. This collision was caused by the northerly, fast-moving Gondwana colliding with the slower-moving southern edge of Laurentia / Baltica. Crustal transpression generated by this collision caused post-Variscan upward doming of the Pennine Arch, Lake District and Cleveland Hills and resulted in significant early Permian erosion. Elsewhere crustal transtension generated by this collision caused Permian volcanism (e.g., Mauchline volcanics in the Midland Valley, the Whin Sill and the Rotliegend volcanics of Poland and Germany). Following this collision (in Mid-Late Permian times) the lithosphere beneath the Variscan Foreland began to cool and both the Southern Permian and Northern Permian Basins (separated by the Mid-North Sea and Fyn-Ringkbing High) were formed. Following these events a period of east-west oriented transtension developed (which was almost certainly related to the earliest North Atlantic opening) and the north-south oriented Central, Viking, Horn, and Oslo Grabens formed (Glennie, 1990). As a result of these large-scale processes major depo-centres were developed in the study area (Cleveland Basin), bounded to the West by the Pennine Arch and the South by the Market Weighton Block (the northern element of the more stable East Midlands Shelf). These depocentres remained active until uplift during the middle Jurassic.

Over much of the UK and the UK Continental Shelf, Mid-Jurassic deltaic and fluvial sediments unconformably overlie marine sediments (the Mid-Cimmerian unconformity). This unconformity was caused by crustal uplift and emergence consequent upon doming in Mid-Jurassic times (e.g. Underhill and Partington, 1993). Following this period of uplift volcanic activity ceased and lithospheric cooling occurred. Cooling caused crustal extension and active graben formation during the Late Jurassic and Early Cretaceous. These effects coupled with sediment loading caused an extensive basin to develop, which controlled subsequent sediment deposition. During the Tertiary the Cleveland Basin suffered inversion. Many of the normal faults appear to have been reactivated as reverse, strike-slip and oblique-slip faults, and contractional structures occur in Chalk sequences. Post-Jurassic deformation was controlled largely by reactivation of older structures that also dominated Jurassic deformation.

The lithostratigraphic nomenclature for Permian to Cretaceous aged sediments in north-east England is complicated due to use of numerous local names for beds, members and formations. The latest revisions used here are tied to both ammonite biostratigraphy and chronostratigraphy (e.g., Cope et al. 1980a, b; Tucker 1991). Other dating schemes are used where appropriate such as those derived from the study of ostracodes (e.g. Bate 1965), palynology (e.g., Hancock and Fisher 1985) and dinocysts (e.g. Riding and Wright 1989, Woollam and Riding 1983). The key stratigraphic intervals encountered on this field trip are given in Figure 1.1

In North East England Lower Jurassic strata (e.g. Staithes Sandstone Formation, Cleveland Ironstone Formation, Whitby Mudstone Formation and Dogger Formation) are predominantly composed of interbedded mudstones and sandstones with rare ironstones. These sediments were deposited on a marine shelf. At the end of the Toarcian there was a period of major erosion, at least in part due to tectonic activity, so the early Aalenian strata rest unconformably on this surface. Regional work on the North Sea (e.g. Underhill and Partington 1993; Partington et al. 1993) suggests that the shallowing which characterises the end of Toarcian deposition and the early Aalenian unconformity (in the field area


7

expressed at the base Dogger Formation) is related to the development of a regional thermal dome situated at the intersection of the Central Graben, Viking Graben and Moray Firth (a triple junction). The following Middle Jurassic sediments (e.g. Saltwick Formation, Cloughton Formation and Scarborough Formation) record the interaction of fluvio-deltaic and marine systems. In general, the source area for the fluvio-deltaic clastics was the Mid-North Sea High (Carboniferous source), with progradation towards the south. Within the Aalenian-Bajocian strata, three major marine incursions are recorded (e.g. the Scarborough Formation) which reflect a number of pulsed, northward-directed transgressions.

Following this period of intercalated deltaic and shallow marine environments in the Mid-Jurassic, sea level rose once more to giving rise to the deposition of the marine mudstones of the Heather and Kimmeridge Clay Formations (Upper Jurassic - Early Cretaceous). Finally, by the End Cretaceous, as eustatic sea-level rise continued and the detrital sediment supply had been largely removed, the nannoplankton-dominated mudstones of the Chalk were deposited (e.g. Burnham Formation).

The sections to be studied are time equivalent to the Dunlin Group and most of the Brent Group in the Brent Province of the North Sea, with production from fields such as Brent, and Dunlin. These Middle Jurassic sandstones contain significant volumes of hydrocarbons, and the coastal sections we visit have been used as outcrop analogues of these prolific reservoirs. Chalk is both a reservoir and a seal, and also contains significant oil discoveries in the North Sea, such as the giant Ekofisk oilfield.

1.6 Selected References

Glennie K.W. (1990) Introduction to the Petroleum Geology of the North Sea. Blackwell. Underhill, J. R. & Partington, M.A. 1993. Jurassic thermal doming and deflation in the North Sea: implications of the sequence stratigraphic evidence. In: Parker, J.R. (ed.) Petroleum Geology of Northwest Europe: Proceedings of the 4th Conference. 337-345. Underhill, J.R. and Partington, M.A. 1993. Use of Genetic Sequence Stratigraphy in Defining and Determining a Regional Tectonic Control on the 'Mid-Cimmerian Unconformity': Implications for the North Sea Basin Development and the Global Sea-Level Chart. In: Weimer, P. & Posamentier, H.W. (eds.). Siliciclastic Sequence Stratigraphy. Am. Assoc. Petrol. Geol. Memoir 58, 449-484.


8

2.0 STAITHES 2.1 Location

Coastal section at Staithes between Staithes Harbour and Old Nab.

Figure 3.1 Location Map

2.2 Grid reference

NZ 784 188 to NZ 794 187 2.3 Depositional environments

Shallow marine (lower shoreface) sandstones, zones of dynamic sediment bypass, mudstones from the offshore transition and from condensed sections.

2.4 Access/logistics

Turn north off A174 towards Staithes, park in public car park at top of hill. Walk down road down into village centre to harbour. Walk eastwards over the wave cut platform past Penny Nab towards the Old Nab. Return to Staithes village by walking westwards over the foreshore N.B. At high tide the sea covers the wave cut platform. Do not walk beyond the Old Nab. The eastern part of the section is cut-off 3 hours before and after high tide (at the steps near to the Staithes beach, well before it covers the majority of the rocky shoreline near the Cleaveland section, so BEWARE. Please take care while walking over the slippery rocks on the wave-cut platform, and do not stand directly under the steep cliffs and watch out for loose rocks on the smaller cliff faces, which can be unstable.

2.5 References to section

Hesselbo and D.N. Parkinson. (1996), Geological Society of London Special Volume 103. 97 - 107. Macquaker, J.H.S. Taylor, K.G. (1996), A sequence stratigraphic interpretation of a mudstone-dominated succession: the Lower Jurassic Cleveland Ironstone Formation, U.K. Geological Society of London Journal, 153. 759- 770


9

2.6 Aims

Describe the rock characteristics and fossils present at this locality and determine the facies, to evaluate the changing processes of deposition. Determine the scale of the stacking patterns and identify the beds, marine flooding surfaces, sequence boundaries and transgressive surfaces in this mud-dominated, shallow marine environment. Assess the petroleum potential for the facies.

2.7 Summary

The rocks exposed at Staithes are the Staithes Sandstone Formation (Pleinsbachian) and the overlying Cleveland Ironstone Formation (Pleinsbachian). The section comprises a succession of marine mudstones (clay-rich, silt-rich, sand-rich mudstones) interbedded with fine-grained sandstones, oolitic ironstones, shell beds and concretionary carbonates.

3.7.1 Staithes Sandstone Formation

Consider: The variation in facies, internal structure and geometry The broad scale changes in sandstone:mudstone ratio. Does this indicate retrogradation, progradation or aggradation. Can you identify

stacking sets? Do the shell lags represent storm lags, transgressive surfaces or sequence

boundaries? Most of the units fine up. Can you identify any signs of abrupt deepening and

therefore marine flooding surfaces? Evaluate the reservoir characteristics of these sandstones. How does this change

vertically and horizontally?

The basal part of the Staithes Sandstone Formation (basal 12 m) comprises an upward-coarsening succession, which is overlain by an overall upward-fining succession (26 m thick). Within these large-scale coarsening- and fining- successions there are smaller-scale upward-coarsening units separated by marine flooding surfaces. Cemented sandstones (N.B. presence of interference ripples) and shell beds (with Gryphaea sp., Oxytoma sp. and Pseudopecten sp.) occur at the levels were the stacking patterns change from overall upward-coarsening to upward-fining. The coarser parts of the succession contain hummocky cross stratification, symmetrical ripple lamination, interference ripples and gutter casts. The relatively poor preservation of the ichnofauna suggests deposition occurred in relatively high energy upper / lower shore face environments.


10

Figure 3.2 Marine ichnofacies


11

Fig: 3.3 Facies present include a mottled grey / tan unit, heaviliy bioturbated, with remnant bedding, showing ripple and low angle lamination. Sand units are characteristically sharp based, gradational tops. The bioturbated unit is overlain by a sharp based fine to very fine grained sandstone, showing characteristic low angle cross lamination, hummocky cross bedding, bioturbated and rippled towards the top. Uppermost unit is thin bedded rippled sandstone and interbedded silty mudstones, bioturbated, with a higher proportion of interbedded sandstone.

Figures 3.4 and 3.5: Close up of the Hummocky Cross Stratification, with smaller scale ripple cross lamination towards the top. Some thin mud drapes record periods of low energy and suspension settling. Rare bioturbation in the HCS sandstones, indicative of high energy and rapid deposition. Bioturbation increases in sandstone above, suggesting lower energy, smaller sandstone units with periods of colonisation and bioturbation.


12


13

Figure 3.6 Ichofauna and depositional environments Fig 3.7


14


15


16

2.7.2 Cleveland Ironstone Formation Consider: The nature of the ironstones, their basal contacts and lateral continuity The stacking patterns revealed by the coarsening upward units Do the ironstones represent periods of transgressive reworking, storm deposits or

condensed intervals during relative sea level fall? Are these sequences or parasequences?

The mudstones in the Cleveland Ironstone Formation vary in grain size from clay- to sand-rich and form upward-fining couplets on a millimetre scale. Individual beds stack into upward-coarsening successions developed on an intermediate (decimetre to metre) scale which are separated from one and another by intervals over which there is abrupt fining (Fig. 2). The intermediate-scale upward-coarsening units themselves stack into large-scale (metre to ten metre scale) upward-fining and upward-coarsening successions (Fig. 2). Scattered concretions, composed of phosphate and berthierene, are present at the levels where the large-scale stacking patterns change from overall upward-fining to upward-coarsening (Fig. 2). The coarse units at the top of the large-scale upward-coarsening successions comprise planar bedded sand-rich mudstones and shelly, oolitic ironstones, contain gutter casts and are commonly intensely bioturbated (e.g., Rhizocoallium isp., Thallasinoides isp.) and shell-rich, siderite and berthierene cemented ironstones. The origin of cements in ironstones has occupied the attentions of geologists for many years (e.g., Macquaker et al., 1996). Recent work, on bacterial zonation in sediments suggests that they are most likely to have precipitated in the iron reduction zone prior to sulphate reduction. Iron reduction:

212Fe2O3 + (CH2O)106(NH3)16H3PO4 + 318H2O

424Fe2 + +106HCO-

3+16NH3 + H3PO4 + 742OH

-

Iron reduction is favoured in conditions where the organic matter is extremely degraded and is a poor substrate (food) for extensive deeper burial bacterial (e.g. by sulphate reducers)

colonisation of the sediment. In such conditions Fe++

concentrations in the pore waters increase and Fe-rich carbonate cements other than pyrite precipitate (e.g. siderite). An unequivocal sequence stratigraphic interpretation of this succession is difficult as the sequence boundaries cannot be identified as there is no evidence of subaerial exposure. In spite of this a) the tops of ironstones are interpreted to be combined sequence boundaries / flooding surfaces, b) the concretions between the large-scale upward-coarsening and upward-fining successions are interpreted to be developed close to the maximum flooding surfaces, c) the large-scale upward-fining successions are interpreted to be transgressive system tracts, d) the large-scale upward-coarsening successions are interpreted to be highstand system tracts and the ironstones themselves are interpreted to be forced regressive system tracts.


17

Fig. 3.4 and 3.5 The Cleveland Ironstone Formation between the Avicula seam and the Raisdale seam. Note the presence of a concretionary layer, three upward-coarsening successions and one upward fining succession. Sequence boundaries / flooding surfaces are interpreted to be located at the top of the ironstones.

UC UF

Ironstones


18

4.0 WHITBY 4.1 Location Cliff and coastal section either side of harbour.

Figure 5.1 Location Map 4.2 Grid reference NZ 897 116 (West Cliff), NZ 905 114 (East Cliff). 4.3 Depositional environments

Fluvio-deltaic coastal plain, fluvial channels, overbank deposits, palaeosols, oolitic ironstones, offshore mudstones.


West Cliff: Park either on the Khyber Pass NZ 898 114, or in one of the car parks in Whitby. The base of the West Cliff is easily accessible via steps from the cafe at the base Khyber Pass. The beach is sandy, and easy to walk on. Do not stand under the cliffs. At high tide the sea come up to the cliff, but there is route out via the slipway 1 hour before, please watch as the tide rises to ensure the route out is still accessible.

East Cliff: Park in the Abbey Car Park NZ 903 114. Walk down the steps into the town. Access to the beach is via steps between the houses. Once on the beach walk northwards towards the footbridge connecting the East Cliff Pier with the mainland. Walk under footbridge and examine rocks on the wave cut platform and in the cliff. N.B. At high tide the sea comes right up to the East Cliff and there is a cut-off point at East Pier it is therefore important to leave the section 2.5 hours before high tide. The cliffs in this area are very dangerous and rock falls are common. Moreover the rocks on the wave cut platform are very slippery. Take care.

4.5 References to section

Alexander, J. and Gawthorpe, R.L. 1993. The complex nature of a Jurassic multi-storey, alluvial sandstone body, Whitby, North Yorkshire. In: North, C.P. and Prosser, D.J. (eds). Characterisation of Fluvial and Aeolian Reservoirs, Geol. Soc. Spec. Publ. 73, 123-142.


19

Macquaker J.H.S. and Raiswell R. (1989) Sedimentology, geochemistry and diagenesis of Toarcian (Jurassic) mudrocks on the Yorkshire Coast of Great Britain. BSRG Field Guide. pp. 8-1 8-18 Macquaker J.H.S. and Gawthorpe R.L. (1993) Mudstone lithofacies in the Kimmeridge Clay Formation, Wessex Basin: Implications for the origin and controls on the distribution of mudstones Journal of Sedimentary Petrology. 63: 1129 - 1143. Raiswell, R. (1987). Non-steady state microbiological diagenesis and the origin of concretions and nodular limestones. In: Marshall, J.D. (ed.). Diagenesis of Sedimentary Sequences. Geol. Soc. Lond. Spec. Publ. 37, 41-54. Underhill, J. R. & Partington, M.A. (1993). Jurassic thermal doming and deflation in the North Sea: implications of the sequence stratigraphic evidence. In: Parker, J.R. (ed.) Petroleum Geology of Northwest Europe: Proceedings of the 4th Conference. 337-345.

4.6 Aims

Compare and contrast the outcrops of the Saltwick Formation either side of Whitby harbour. Assess reservoir architecture and heterogeneity. Discuss controls on depositional thickness and facies?

4.7 Summary Whitby West Cliffs expose a ~3 5m thick succession the Middle Jurassic Saltwick Formation which is dominated by a complex multi-storey sandbody. The Whitby Fault runs approximately N-S through the town, downthrows to the west and separates the successions in the east and west cliffs. Estimated throw of the fault is c. 12 m on the base of the Dogger Formation. The succession in the East Cliff comprises Early and Middle Jurassic strata including the Whitby Mudstone, Dogger, Saltwick and Eller Beck Formations.

3.7.1 Whitby Mudstone Formation The lower part of the Whitby Mudstone Formation (Alum Shale Member) is exposed in the East Cliff and is dominated by mudstones and siltstones with abundant pyrite-rimmed calcite and siderite concretions. It contains a marine macrofauna with belemnites, bivalves e.g., Dacryomya sp., Pleuromya sp., ammonites Hildoceras sp. and Dactylioceras sp., and zones of bioturbation by Planolites isp., Chondrites isp. and Phycosiphon isp. Ammonites suggest that the Alum Shale Member at this locality belongs to either the bifrons zone or older units (Knox 1984). The concretions present within these marine mudstones probably precipitated close to the sediment / water interface (certainly prior to compaction and probably within the top few metres). In this setting cementation probably occurred as a consequence of the bacterial degradation of organic matter (sulphate reduction and methanogenesis) in association with breaks in sediment accumulation (e.g., Raiswell, 1987; Macquaker and Raiswell, 1989; Macquaker and Gawthorpe, 1993). Organic matter oxidation by sulphate reduction:

2CH2O + SO

2-

4 H

++ 2HCO

-

3+ HS

-

Pyrite formation by sulphate reduction:

2Fe2O

3+ 4SO

2 -

4+ 9CH

20 4FeS + 9HCO

-

3+ 4H

2O + H

+

Calcite precipitation:

Ca++

+ HCO-

3+OH

- CaCO3+ H

2O


20

Methanogenesis:

2CH2O CH

4+CO

2

4.7.2 Dogger Formation The Dogger Formation is thin, 0.5 m thick, intensely bioturbated sandstone with Diplocraterion isp, Phycosiphon isp. Teichichnus isp, Thalassinoides isp., Skolithos isp., Palaeophycus isp, Planolites isp. and rootlets. It forms a prominent, cemented bench along the East Cliff which is locally incised by fluvial channels of the overlying Saltwick Formation. The Dogger has been dated from rare ammonites either as wholly within the murchisonae zone or possibly extending down into the uppermost parts of the opalinum zone; and thus there is considerable incision at the base of the Dogger, with several ammonite biozones absent. This unconformity is the Mid-Cimmerian unconformity and was probably produced by mid-Jurassic North Sea doming (e.g. Underhill and Partington, 1993) 4.7.3 Saltwick Formation The nature of the Saltwick Formation changes markedly across the outcrop belt (Alexander & Gawthorpe 1993). The complex sandbody in Whitby West Cliff (Fig. 5) is dominated by sandstone, whereas the East Cliff is dominated by fine-grained deposits which consist of stacked palaeosols and pedogenically altered sheet sandstones. In the lower part of the Saltwick Formation, there are drifted plant bed horizons with a diverse flora (Whitby Plant Bed) and occasional freshwater shell beds with Unio sp. present. Fig. 5.2: Location map of Whitby East and West Cliff (from Gawthorpe and Alexander 1993).


21

Fig 5.3: Stratigraphic summary of the Saltwick Formation (from Gawthorpe and Alexander 1993).


22


23

Figure 5.4 Possible geometries of the sand bodies / architectural elements (from Gawthorpe and Alexander 1993).


24

Figure 5.5 Schematic depositional environment (from Gawthorpe and Alexander 1993).


25

Figure 5.6 Lithofacies and permeability distribution (from Gawthorpe and Alexander 1993).


26

6.0 Flamborough Head 6.1 Location

Figure 6.1 Location maps 6.2 Grid reference TA154755 TA200685

FLAMBOROUGH HEAD

OS Grid Reference: TA154755TA200685

Introduction

The Flamborough Head GCR site comprises 17 km of sea cliff and rock platform sections on the

north Yorkshire coast. These cliffs expose a continuous Northern Province Chalk succession

from the base of the Upper Cretaceous Series, in the Hunstanton Red Chalk Formation at

Speeton Cliff, up to the lower part of the Lower Campanian succession, at the top of the

preserved Flamborough Chalk Formation at Sewerby Steps (Figures 5.19 and 5.20). Even

higher (low Lower Campanian) Flamborough Chalk successions are exposed in quarries on the

Yorkshire Wolds. From the Santonian strata upwards the succession is enormously expanded

compared with its Southern Province equivalents.

Figure 5.19: Location of key sections in the Flamborough Head GCR site.

Extracted from the Geological Conservation Review

You can view an introduction to this volume

at http://www.jncc.gov.uk/page-2731

JNCC 19802007

Volume 23: British Upper Cretaceous Stratigraphy

Chapter 5: Northern Province, England

Site: FLAMBOROUGH HEAD (GCR ID: 211)

1

10/ 10/ 2011 13:10flamborough head - Google Maps

Page 1 of 1http:/ / maps.google.co.uk/ maps?f= q&source= s_q&hl= en&geocode= n= 0.121166,0.349846&t= m&z= 12&ei= JeCSTofVG8Tg8gO38oz_CA&pw= 2

Address Flamborough HeadFlamborough, East Riding ofYorkshire YO15 1, UK

2011 Google -


27

6.3 Depositional environments Marine chalk deposits, with well exposed lithixtid and hexactinellid sponge beds. In places heavily fractured and karstified.


Section to be examined are in Selwick Bay (see map). Access is via path, steps. Care to be taken when walking on slippery surface and over boulders and rocks. The cliff sections are unstable and care to be taken when beneath them . Hard hats to be worn at all times.

6.5 References

Lamplugh, G.W. (1880), On a fault in the Chalk of Flambro Head with some nores of the drift of the locality. Proceedings of the Yorkshire Geological and Polytechnical Society, 7, 242-245

Starmer, I.C., (1995a), Deformation of the Upper Cretaceous Chalk at Selwicks Bay, Flamborough Head, Yorkshire: its significance in the structural evolution of north-eat England and the North Sea Basin. Proceedings of the Yorkshire Geological Society, 50, 213-28

6.6 Aims

Describe the lithological characteristics of chalk, and assess reservoir / seal potential. In particular observe the influence of faulting and fracturing to enhance permeability and reservoir performance.

6.7 Summary The cliff section at Selwick Bay exposes Cretaceous chalk that has been deformed by a series of faults. The nature of faulting is still debated. Early workers (Lamplugh 1880), presented a simple model, with normal faults downthrowing to south with a 24m throw. However more recently it has been interpreted to be a complex folded and faulted zone, produced by east-west thrusts associated with movement along the Dowsing Fault line (Starmer 1995a). The latter interpretation is not accepted by all workers. The faults in the Selwick Bay produce a disturbed zone bringing Flamborough Chalk against Burnham Chalk. The resultant fracture network is extensive. We will discuss the role of fractures in reservoir production, and prediction of fractures in the subsurface.


28

Figure 6.2 Stratigraphy of the Cretaceous Chalk

Part 1 includes Speeton CliffBuckton Cliffs. This magnificent section through the HunstantonRed Chalk Formation and Ferriby Chalk Formation (Figures 5.3, 5.205.25), exposes acontinuous succession from the AlbianCenomanian boundary.

Figure 5.3: The stratigraphy of the Northern Province Chalk (compare with Figure 1.5,Chapter 1 and Figures 2.8, 2.9, 2.21, 2.22 and 2.27, Chapter 2).

Part 2 comprises the vertical cliffs and scars (rock platforms) from Speeton Cliff and Buckton

Cliffs eastwards to Stottle Bank in the Welton Chalk and Burnham Chalk formations. These

cliffs include the Royal Society for the Protection of Birds (RSPB) bird reserve at Bempton Cliff,

and the structurally complex area known as Staple Nook' or Scale Nab', which areinaccessible. However, it is possible, but with great difficulty, to walk at extreme low water

along the boulder-strewn beach at the foot of the cliffs from Speeton Cliff as far as Staple Nook

(adjacent to Scale Nab). Beyond Staple Nook the remainder of the traverse through Sanwick

Bay (Rowe, 1904, pl. 27) is prevented by deep-water caves and inlets. The first access to the

shore is at Little Thornwick Bay. Here, and in the adjoining Great Thornwick Bay and North

Landing, there are excellent sections in the cliffs and scars of the composite succession from

the Barton Marls in the Welton Chalk Formation, to the Ulceby Marl and Oyster Bed, near the

base of the Burnham Chalk Formation. In the 1.8 km stretch from the eastern headland of

North Landing to Stottle Bank, 0.5 km north of Selwicks Bay, there is no access to the shore.

Part 3 includes the highest part of the Burnham Chalk which is exposed between Stottle Bank,

where the cliff-line changes from NWSE to northsouth, and Selwicks Bay, where basal(flintless) Flamborough Chalk Formation, on the west side of the bay, is brought into

juxtaposition with flinty Burnham Chalk, on the east, by the Selwicks Fault complex.

Part 4 comprises the highest Burnham Chalk Formation and the complete (flintless)




JNCC 19802007




4




JNCC 19802007




9

Figure 5.4: Key marker beds at the WeltonBurnham Chalk boundary, North Landing,Flamborough Head GCR site, Yorkshire. (Photo: C.J. Wood.)

Mortimer (1878) first drew attention to the vertical columns of flint (paramoudras) at the base

of the cliffs on the east side of the bay. Rowe (1904) stated that six such flints could be seen

from the sea to the south-east of North Landing, noting that they characterized a level in the

upper part of his Holaster planus Zone. It is now known that paramoudras are relatively

common everywhere in the Sternotaxis plana Zone at this level, i.e. in the interval with closely

spaced thick tabular flints between the Wootton Marls and the Ulceby Marl. However, they are

relatively inconspicuous in the degraded inland quarry sections, and North Landing is by far the

best place to study them. Some of the detached, wave-rounded, paramoudras lying on the

beach here display a complex internal structure. Paramoudras reappear low in the Micraster

cortestudinarium Zone, above the Kiplingcotes Marls, notably the famous flint formerly seen in

Ashby Hill Quarry (TA 2405 0060) in Lincolnshire (Toynton and Parsons, 1990).

Biostratigraphy

Barrois (1876) was the first geologist (28 years earlier than Rowe) to use fossils to subdivide

this composite section into zones. His pioneering work was remarkably correct by today's

standards. He recognized that the chalk in Little and Great Thornwick Bay must belong to the

Terebratulina gracilis (i.e. lata) Zone because of the general rarity of macrofossils, apart from

the inoceramid bivalve Inoceramus brongniarti (i.e. I. ex gr. lamarcki Parkinson). Even more

importantly, he appreciated that the very hard, siliceous, crystalline chalk' in North Landing,with closely-spaced, smokey-grey, predominantly tabular flints' (his Chalk with grey flints ofNorth Sea') contained fossils indicative of the Holaster planus Zone, including the zonal index

fossil. Rowe (1904) actually recorded 30 examples of Sternotaxis plana from here, noting that

it was common'. It is surprising that there are no records of Micraster, since M. corbovisForbes occurs regularly at this level in inland pits in Yorkshire and in Lincolnshire. Barrois noted

this same distinctive flinty unit (i.e. basal Burnham Chalk Formation) at the top of the Bempton




JNCC 19802007




20


29

Figure 6.3a,b,c: Views of Flamborough head showing typical bedding in the chalk, and extensive fracturing.

ammonite Zone of the Southern Province is completely missing at the hiatus marked by the

sub-Totternhoe Stone erosion surface (cf. Mitchell, et al., 1996, fig. 3).

Part 2: Welton Chalk and Burnham Chalk formations (Buckton Cliffs to StottleBank)

At the eastern end of Buckton Cliffs, the dip brings the boundary between the Ferriby Chalk

and Welton Chalk formations down to sea level, close to a wave-washed point known as KitPape's Spot' (TA 1886 7454). To the west of this point (TA 1868 7460), there is considerable

tectonic complication, with the base of the flinty Welton Chalk being locally thrust over the

Black Band. The flintless, shell-detrital chalk that normally intervenes between the Black Band

and the lowest flinty chalk is here represented merely by fragments incorporated in the crush-

zone associated with the thrust plane. A conspicuous vertical fault recorded by Rowe (1904) in

the cliff near this point had a throw of only about 4 ft (1.2 m), but exhibited horizontal

slickensiding aligned S20E, indicating a predominantly lateral displacement. This sense ofmovement is the same as that shown by the thrust. Nearby sections here (e.g. Rowe, 1904, pl.

19) show a normal succession above the Black Band, although the flintless chalk component

appears to be somewhat thinner (c. 3.5 m) than the 45 m found elsewhere. However, Rowesuggested that this reduction in thickness was due to compaction.

Sherborn's longitudinal cliff section (Rowe, 1904, pl. 38) showed that chalk with tabular flints

(identified as the Holaster planus Zone) occupied the higher part of the cliffs between the

eastern end of Buckton Cliffs and a point, Gull Nook (TA 218 728). Beyond Gull Nook, the cliff

reduced in height towards Little Thornwick Bay, so that successively lower levels of the

underlying (Welton) Chalk appeared in the top of the cliff. This is partly confirmed from oblique

aerial photographs, in which the up-section change, from the massive-bedded chalks of the

Welton Chalk Formation, to the thin-bedded chalks with closely spaced tabular flints of the

Burnham Chalk Formation, can be clearly seen (Figure 5.25), as can two closely spaced

crevices some distance below which represent the paired Deepdale Marls (Figure 5.26).

However, the succession may extend much higher than in Sherborn's interpretation. Somewhat

higher than the base of the thin-bedded chalks, and only two-thirds of the way up the cliff, the

lithological change (within the Sternotaxis plana Zone) at the Ulceby Marl from darker, very

hard chalks, to paler and relatively softer chalks, can be confidently identified at a conspicuous

recess on top of a ledge. Above this marl an additional c. 30 m of chalk can be inferred.

Figure 5.25: Looking east onto the cliffs at North Landing, Flamborough Head, Yorkshire,where the WeltonBurnham Chalk boundary is well exposed. Spectacular Paramoudraflints are present in the basal unit of the Burnham Chalk Formation. (Photo: C.J. Wood.)




JNCC 19802007




17

Figure 5.30: Formation of sea stacks and the Flamborough Fault Zone at Selwicks Bay,Flamborough Head, Yorkshire. (Photo: Cambridge University Collection of AerialPhotography: copyright reserved).

In Figure 5.29, previously unpublished logs of the cliff sections from Stottle Bank to Kindle

Scar, from the south side of Selwicks Bay on the south side of the Selwicks Bay Fault, and at

Flamborough Head, are correlated. Thin, poorly developed white flints are found in the Selwicks

Bay section in the basal Flamborough Chalk Formation, some metres above the terminal

Burnham Chalk flint (High Stacks Flint), but are absent from the section at High Stacks at

Flamborough Head. The correlation of the higher Burnham Chalk Formation succession

between Flamborough Head and the section immediately north of Kindle Scar (c. 0.5 km) is

unequivocal. In each an unnamed pair of marls, 0.3 m apart, and a semi-continuous nodular

flint, are seen 1.5 m and 3.7 m below the High Stacks Flint respectively. There is also a very

tight correlation between the Burnham Chalk section on the south side of Selwicks Bay and

that at Stottle Bank, although there is some problem with correlating the flints in the higher

part of the Selwicks Bay section. These section details and correlations differ significantly from

those presented by Whitham (1993, fig. 4).

Biostratigraphy

The biostratigraphy of the highest Burnham Chalk in these sections is extremely poorly known.

Professor A.S. Gale (unpublished data) has collected specimens of the thin-shelled inoceramid

bivalve Cladoceramus undulatoplicatus (Roemer) (now at the British Geological Survey,

Keyworth) at two horizons beneath the unnamed marl seam on the south side of Selwicks Bay,

allowing this part of the succession to be assigned to the basal Santonian Cladoceramus

undulatoplicatus Zone of the standard European zonal scheme. About 1 m above the highest

occurrence of Cladoceramus, he collected specimens of the echinoid Infulaster infulasteroides

(Wright and Wright) (common over 1 m), terebratulid brachiopods (Gibbithyris sp.) and other

inoceramid bivalves that are possibly Sphenoceramus cardissoides (Goldfuss). About 10 m

above the marl, in the section immediately north of Kindle Scar, the occurrence of

Cordiceramus cordiformis (J. de C. Sowerby) (British Geological Survey collections,

unpublished) in fossiliferous, inoceramid bivalve-rich chalk over about 4 m suggests a

correlation with the Cordiceramus-acme in the Middle Santonian strata of northern Germany

(Ernst, 1966; Ernst and Schulz, 1974), and indicates a possible upper limit to the Lower

Santonian succession. This would fall in the higher part of the coranguinum Zone of the

Southern Province. It is not possible at present to identify the BurnhamFlamboroughboundary on a faunal basis. However, since it is known that the base of the Uintacrinus socialis

Zone is situated 70 m above the High Stacks Flint, it is clear that the higher part of the

equivalent of the coranguinum Zone, both the flinty (Burnham) and flintless (Flamborough)

components, is enormously expanded here compared to its development in the Southern

Province (about 87 m compared with 32 m from the base of the Santonian to Buckle Marl 1 at

Seaford Head (Cuckmere to Seaford GCR site), Figures 3.100 and 3.101, Chapter 3).




JNCC 19802007




25


30

Figures 6.4 a,b,c The disturbed zone at Selwicks Bay, Flamborough Head. A series of faults displace the chalk by 23m to south.

marks the approximate position of the base of the Santonian portion of the coranguinum Zone

(see below), it is more likely that Rowe and Sherborn's marker is the Middleton Marl (i.e. near

the top of the Coniacian portion of the zone), or that the latter marl is represented by the deep

crevice, seen 13 m beneath the basal Santonian marker marl, at the base of the deep water

gully at Stottle Bank itself. This latter interpretation fits with the record of Cladoceramus in

NIREX Borehole 37 in north Lincolnshire, 12 m above the Middleton Marl.

Part 3: Stottle BankSelwicks BayFlamborough Head (High Stacks)

Stottle Bank to Flamborough Head crosses the complex tectonic structures related to faulting

in Selwicks Bay (Figures 5.285.30). The faulting and folding is related to eastwest thrustsinitiated as frontal movements from the offshore Dowsing Fault.

Figure 5.28: The disturbed zone' at Selwicks Bay, Flamborough Head, Yorkshire. Theseries of faults displaces the chalk by 23 m down to the south, bringing FlamboroughChalk against Burnham Chalk. (Photos: R.N. Mortimore.)




JNCC 19802007




22


31

Figure 6.5 Stratigraphy at Selwicks Bay, showing location of fault zone. Figure and Plates for Flamborough Head extracted from the Geological Conservation Review http://jncc.gov.uk :

Lithostratigraphy and tectonic structures

The previously unpublished c. 30 m section (Figure 5.29) begins in the Burnham Chalk at the

lowest point that can be seen in the water-filled gully at the base of Stottle Bank, and extends

to the High Stacks Flint, which is found near the base of Kindle Scar, and at the base of the

West Cliff in Selwicks Bay. The High Stacks Marl (Whitham, 1993, fig. 5), 3.3 m above this

flint, forms a conspicuous crevice at the foot of the cliff at the back of the bay. Above this level,

extensive faulting breaks up the basal Flamborough Chalk succession. In the centre of the bay,

a complex, brecciated, calcite-veined fault zone is seen in the cliffs, and can be traced

seawards on the scars. This is the Selwicks Bay Fault of the earlier literature. On the south side

of the bay, on the far side of this fault, flinty chalk of the Burnham Chalk Formation is seen at

the base of the scars at low water, and chalk with flints continues to the top of the cliff,

although some of the flints are relatively inconspicuous.

Figure 5.29: Correlation from Stottle Bank across the Selwicks Bay Fault to FlamboroughHead (High Stacks) with inferred biostratigraphy.

The early workers (e.g. Lamplugh, 1880, 1895), presented a relatively simple structural picture

of Selwicks Bay, in which flintless (i.e. Flamborough Chalk Formation) chalk was brought into

juxtaposition with flinty (Burnham) chalk by the Selwicks Bay Fault, the extent of the vertical

downthrow being determined as about 80 ft (24 m) to the north. However, Starmer (1995a)

has demonstrated that Selwicks Bay itself (as well as the cliffs to the north) is structurally

extremely complex, with the chalk having undergone four temporally widely separated phases

of deformation, including folding, faulting and thrusting (Figures 5.28 and 5.30). In his

analysis, he claimed to have traced the highest flint (High Stacks Flint) close to the main fault,

which he termed the Frontal Faults' (of the entire complex), and assigned to the fourth phaseof deformation. He considered that there was actually no significant vertical displacement, and




JNCC 19802007




23

pet eng field guide 2014

Documents

field course

times field trip participants

field trip leaders

field work location

hotel details

location maps

times participants

safety form