LEC1 Courteenhall Phase 2 - British Geological Survey · LEC1 Courteenhall Phase 2 Geological Survey of SSSI June 2017 J Murphy & Sons Limited Wigan Road Goldborne Warrington Cheshire

LEC1 Courteenhall Phase 2

Geological Survey of SSSI

June 2017

J Murphy & Sons Limited

Wigan Road

Goldborne

Warrington

Cheshire

WA3 3UB

2015s3092 Courteenhall SSSI Geological Survey i

JBA Project Manager The Old School House St Joseph's Street TADCASTER North Yorkshire UNITED KINGDOM LS24 9HA

Revision History

Revision Ref / Date Issued Amendments Issued to

Rev.0 / June 2017 - Jamie Rothwell

Contract This report describes work commissioned by Jamie Rothwell on behalf of J Murphy & Sons Ltd. James Howard of JBA Consulting carried out this work.

Prepared by .................................................. James Howard BSc MSc PhD FGS

Senior Engineer

Reviewed by ................................................. David Gwede BSc MSc CEng MICE Peng BGA

Technical Director

Purpose This document has been prepared as a Draft Report for J Murphy & Sons Ltd. JBA Consulting accepts no responsibility or liability for any use that is made of this document other than by the Client for the purposes for which it was originally commissioned and prepared.

JBA Consulting has no liability regarding the use of this report except to J Murphy & Sons Ltd.

2015s3092 Courteenhall SSSI Geological Survey ii

Copyright © Jeremy Benn Associates Limited 2017

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Contents

2015s3092 Courteenhall SSSI Geological Survey

1 Introduction ............................................................................................................ 1

2 Previous geological studies ................................................................................... 1

3 The current project ................................................................................................. 3

3.1 Aims and Objectives .......................................................................................................... 3 3.2 Proposed engineering works .............................................................................................. 3 3.3 Methodology....................................................................................................................... 3

4 Geological Description ........................................................................................... 4

4.1 LEC8Loc1 .......................................................................................................................... 4 4.2 LEC8Loc2 .......................................................................................................................... 7 4.3 LEC8Loc3 .......................................................................................................................... 10 4.4 LEC8Loc4 .......................................................................................................................... 14

5 Geological assessment.......................................................................................... 18

5.1 Exposure quality and units identified .................................................................................. 18 5.2 Proposed correlations ........................................................................................................ 18

6 Conclusions ........................................................................................................... 22

References.......................................................................................................................... 23

2015s3092 Courteenhall SSSI Geological Survey

List of Figures Figure 1-1: Geological cross-section through Roade Cutting. .......................................... 2

Figure 4-1: General view showing locality 1. .................................................................... 6

Figure 4-2: View showing beds 1-4 at locality 1. .............................................................. 6

Figure 4-3: General view showing very poor exposure at locality 2. ................................ 9

Figure 4-4: General view showing locality 3. .................................................................... 12

Figure 4-5: View showing beds 1 to 7 at locality 3. .......................................................... 12

Figure 4-6: View showing beds 1 to 10 at locality 3. ....................................................... 13

Figure 4-7: View showing locality 9. ................................................................................. 16

Figure 4-8: View showing beds 1 to 6 in locality 4. .......................................................... 16

Figure 4-9: View showing beds 3 to 4 in locality 4. .......................................................... 17

Figure 4-10: View showing beds 7 to 9 in locality 4. ........................................................ 17

Figure 5-1: Photo montage showing the localities studied and proposed correlation. ..... 20

Figure 5-2: Proposed correlation between the localities studied. ..................................... 21

List of Tables Table 4-1: LEC8Loc1 text log ............................................................................................ 4

Table 4-2: LEC8Loc2 text log ............................................................................................ 7



2015s3092 Courteenhall SSSI Geological Survey 1

1 Introduction This report describes the bedrock exposed between mileage 60.0050 and 60.1630 on the southwest side of Roade cutting south of Bridge 211 (Courteenhall Road Bridge). The description of the site is required as a record of its current condition prior to installation of remedial works on the slope in 2017. The exposed strata belong to the Blisworth Limestone Formation of the Great Oolite Group and were deposited during the Middle Jurassic. The report provides stratigraphic logs and descriptions of the strata identified, photographs and a panorama recording the current condition of the outcrop and a proposed correlation between the locations studied. A tentative correlation with sections studied by the BGS (Barron & Woods 2010a, b) is proposed.

The outcrop within the study area is generally poor being limited to small, strongly weathered exposures in the upper part of the slope. Exposed rock is typically loose and unstable. Access to the exposures required use of roped access techniques. No outcrop is accessible from the trackside.

2 Previous geological studies Roade cutting was excavated in the 1830's and subsequently widened in about 1880. The cutting exposes a nearly complete succession of Bathonian (Middle Jurassic) strata. This sequence is probably unique in the East Midlands and the cutting is therefore designated as a SSSI (Barron & Woods 2010b). The first geological description was provided by Woodward (1894, p. 339). Following instability, substantial engineering works were completed in the 1890's. A comprehensive geological description of the strata exposed during this phase of engineering works is provided in Thompson (1924). Thompson (1924) produced a geological profile through the cutting which was subsequently updated and amended by Barron & Woods (2010b), this profile is reproduced in Figure 1-1 to provide a context for the current study. Retaining walls, superficial deposits and vegetation growth now obscure softer deposits and only the limestone dominated units are exposed.

Barron & Woods (2010a, b) provide detailed descriptions and correlations of exposures in Roade Cutting between bridges 208 and 210. They report a 6.5m high outcrops along both sides of the cutting exposing sub-horizontal beds of well bedded, pale coloured fossiliferous bioclastic and peloidal limestones. These units are considered to correlate with beds 10-18 of Thompson (1924). Barron & Woods (2010b) assign these units to two members; the Roade Member and the Ardley Member based on fauna and vertical changes in lithology.


Figure 2-1: Geological cross-section through Roade Cutting adapted from figure in Barron &

Woods (2010b), originally drafted by Thompson (1924).

Exte

nt

of

surv

ey

com

ple

ted b

y B

arr

on &

W

oods (

2010a,

b).

Exte

nt

of

curr

ent surv

ey


3 The current project

3.1 Aims and Objectives

The aim of the current report is to provide a modern description of the geology exposed between mileage 60.0050 and 60.1630 on the southwest side of Roade Cutting prior to remedial works to stabilise the slope in 2017.

The objectives are

• To identify suitable exposures within the study area.

• To record the geology exposed with a focus on the lithostratigraphy, biostratigraphy and palaeontology.

• To provide a correlation between units exposed on the site and, where possible, between the modern stratigraphy proposed by Barron & Woods (2010b).

3.2 Proposed engineering works

Roade cutting extends over a total length more than 2800m. Four rail lines pass through Roade cutting, these comprise the Up and Down 'Fast' lines of the LEC (West Coast Mainline) on the south-east side and the Up and Down 'Slow' lines of the HNR (Northampton Loop) on the northeast side. Both lines are electrified. North of Bridge 210 the level of the HNR falls relative to the LEC. The cutting reaches its maximum depth of approximately 23m on the northeast side of the HNR at bridge 211 opposite the present study location. It is at this location which Thompson (1924) reported the stratigraphically lowest beds.

The current engineering works extend between mileage 60.0050 and 60.1630 to the south of Bridge 211. The works comprise de-vegetation of the slope and installation of soil nails and steel mesh to stabilise the slope and prevent rockfalls. Future access to the cutting will be challenging, especially when vegetation is re-established.

3.3 Methodology

Following de-vegetation of the cutting face the slope was inspected from above and locations to be logged were identified. Large vegetation was cleared but no additional preparation of the exposures was undertaken prior to the geological logging. Exposure is limited and is restricted to the upper part of the cutting slope. The available exposures are poor with extensive weathering and surface vegetation (moss and lichen). Access to the sections required the use of roped access techniques supervised by Force Contracting Services due to site access restrictions, the geological inspection was completed by James Howard of JBA Consulting over two visits on the 28th February 2017 and 9th March 2017.

Four localities were measured, described and photographed in detail. Following the convention established by Barron & Woods (2010b) the section is named LEC8 and the locations numbered LEC8Loc1 to LEC8Loc4. At each locality beds were numbered on a bed by bed basis and Samples collected were assigned JBA sample numbers in the following format "JBA-LEC8Loc(X)-S(X)". Samples were cleaned using water and a brush to remove soil and surface vegetation and were described using a hand lens.

Where possible geological descriptions follow the conventions of Barron & Woods (2010b).


4 Geological Description

4.1 LEC8Loc1

NGR: SP 74690 52996 SP (logged 28/02/17)

Table 4-1: LEC8Loc1 text log

Proposed Stratal unit (After Barron & Woods (2010b)

Local bed number

Description Thickness (m)

F

TOP OF SECTION AS SEEN

1a LIMESTONE, white 2.5Y 8/1, peloidal bioclastic wackestone oyster shells Praeexogyra and bioturbation. (JBA-LEC8Loc1-S1)

0.28 seen

1b LIMESTONE, light grey 2.5Y 7/1, medium grained peloidal grainstone with ooids oyster shells Praeexogyra, bivalves and common Echinoderm spines. Peloids commonly light brown. (JBA-LEC8Loc1-S2)

0.18

3 MUDSTONE light grey, strongly weathered.

0.03

4 LIMESTONE, light grey 2.5Y 7/1, medium grained peloidal grainstone with shell fragments. (JBA-LEC8Loc1-S3)

0.17

SECTION GAP 0.40

E

5a LIMESTONE, light grey peloidal bioclastic grainstone with brachiopods and rare lithic grains. Peloids commonly light brown.

0.09

5b LIMESTONE, Light grey 2.5Y 7/1, peloidal bioclastic grainstone with rare lithic grains. Peloids commonly light brown. (JBA-LEC8Loc1-S4).

0.11


0.05

BASE OF SECTION AS SEEN


4.1.1 Graphic log

0

1

1.5

0.5

1

2

3 4

5

6


4.1.2 Photographs

Figure 4-1: General view showing locality 1.

Figure 4-2: View showing beds 1-4 at locality 1.

2

4

3

1

6

5

4

3

2

1


4.2 LEC8Loc2

NGR: SP 74693 52994 (logged 28/02/17)



Local bed number



F

1 LIMESTONE, light grey 2.5Y 7/1-2, peloidal fine and medium grained bioclastic packstone. (JBA-LEC8Loc2-S1)

0.08 seen

2 LIMESTONE, white 2.5Y 8/1, peloidal bioclastic grainstone, laminated with ooids, bivalves and whole oyster shells Praeexogyra and gastropods Nerinea. (JBA-LEC8Loc2-S2)

0.15

3 LIMESTONE, light grey medium grained packstone with ooids and brachiopods.

0.07

4a LIMESTONE, light grey fine grained peloidal grainstone. Peloids commonly light brown.

0.06

4b LIMESTONE, light grey 2.5Y 7/1-2, fine grained peloidal grainstone with rare small brachiopods. Peloids commonly light brown. (JBA-LEC8Loc2-S3)

0.07

4c LIMESTONE, light grey fine grained peloidal grainstone. Peloids commonly light brown.

0.08

5 MUDSTONE dark yellowish brown, strongly weathered.

0.02

6a LIMESTONE pale yellow 2.5Y 8/2, peloidal bioclastic packstone with rare ooids. Rare gastropods Nerinea. (JBA-LEC8Loc2-S4)

0.14

6b LIMESTONE, light grey 2.5Y 7/1, medium grained, massive, pelodal, bioclastic packstone with bivalves and oyster shells Praeexogyra. (JBA-LEC8Loc2-S5)

0.08 seen



4.2.1 Graphic log

0

1

0.5

4a

6a

6b

5 4c

4b

3

2

1


4.2.2 Photographs

Figure 4-3: General view showing very poor exposure at locality 2.

1

2

3

4

5 6


4.3 LEC8Loc3

NGR: SP 74664 53031 (logged 10/03/17)



Local bed number



F

1 LIMESTONE pale yellow peloidal bioclastic packstone. Peloids commonly light brown.

0.40 seen

2 MUDSTONE light grey laminated, strongly weathered.

0.05

3 LIMESTONE, light grey medium coarse grained, thinly bedded, pelodal, bioclastic packstone with brachiopods and bivalves.

0.05

4 LIMESTONE, light grey 2.5Y 7/1, medium coarse grained ooidal, bioclastic packstone with frequent bivalues and gastropods Nerinea and rare lithic grains. (JBA-LEC8Loc3-S1)

0.25

5 MUDSTONE light grey laminated, strongly weathered.

0.05

6 LIMESTONE, light grey 2.5Y 7/1, coarse grained peloidal grainstone with rare ooids. (JBA-LEC8Loc3-S2)

0.10

7 LIMESTONE, light grey 2.5Y 7/1-2, coarse grained peloidal packstone with rare ooids. (JBA-LEC8Loc3-S3)

0.15


0.05

9 LIMESTONE, light grey coarse grained, pelodal, bioclastic packstone with bivalves and oyster shells Praeexogyra.

0.10

10 LIMESTONE light grey 2.5Y 7/1-2, medium coarse grained peloidal bioclastic packstone. (JBA-LEC8Loc3-S4)

0.25



4.3.1 Graphic log

0

1

1.5

8

3 2

1

0.5

4

5

6

9

10

7


4.3.2 Photographs

Figure 4-4: General view showing locality 3.

Figure 4-5: View showing beds 1 to 7 at locality 3.

3

7

5

6

2

1

4


Figure 4-6: View showing beds 1 to 10 at locality 3.

2

3

10

9

5

6

4

7

8

1


4.4 LEC8Loc4

4.4.1 Text log

NGR: SP 74655 53042 (logged 10/03/17)



Local bed number



1 LIMESTONE, light grey 2.5Y 7/1, coarse grained peloidal packstone with rare ooids.

0.11

F

2a LIMESTONE, white 2.5Y 8/1, bioturbated peloidal packstone with oyster shells Praeexogyra, articulated bivalves, Echinoderm spines, rare ooids and lithoc grains. Peloids commonly light brown. Upper surface irregular. (JBA-LEC8Loc4-S1)

0.29 seen

2b LIMESTONE, white peloidal weakly bedded packstone with articulated bivalves, Echinoderm spines and rare ooids. Peloids commonly light brown.

0.16

3 LIMESTONE pale yellow 2.5Y 8/2, medium grained thinly bedded bioclastic packstone with oyster shells Praeexogyra, gastropods Nerinea, brachiopods Terebratula, rare ooids and patchy sparite, weathers pale orange. (JBA-LEC8Loc4-S2)

0.35

E

4 MUDSTONE, light yellow laminated, strongly weathered, bioclastic.

0.28

5 LIMESTONE, light grey thinly bedded peloidal packstone.

0.17

6 MUDSTONE, light yellow laminated, strongly weathered.

0.12 (Seen)

SECTION GAP 1.13

7 LIMESTONE, dark brown, medium coarse peloidal, coarse bioclastic grainstone, tabular crossbedding.

0.15 (seen)

8 MUDSTONE, light grey laminated strongly weathered, bioclastic

0.20

9 LIMESTONE, light grey 2.5Y 7/1 laminated peloidal packstone with bivalves. (JBA-LEC8Loc4-S3)

0.15



4.4.2 Graphic log

0

1

1.5

0.5

5

7

4

8

9

2.5

1.5

2

3

3

2b

2a

1

6


4.4.3 Photographs

Figure 4-7: View showing locality 9.

Figure 4-8: View showing beds 1 to 6 in locality 4.

6

4

5

2

1

3

1-6

7-9




8

7

9


5 Geological assessment

5.1 Exposure quality and units identified

Bedrock exposures in the area studied are restricted to the upper part of the slope (Figure 5-1). The exposures are small and typically strongly weathered with moss and lichen cover. The exposed strata belong to the Blisworth Limestone Formation with neither the top or the base of the formation exposed. The strata have been divided into a lower and upper unit based on sedimentology, lithology and fossil assemblages.

5.1.1 Lower unit

The lower unit was observed in locations LEC8Loc1 and LEC8Loc4 and comprises a succession of interbedded peloidal packstone, grainstone and mudstone. The packstones are medium to coarse grained and medium grained peloidal and typically laminated or thinly bedded. Some contain bioclasts and bivalves but these limestones are typically less fossiliferous than the overlying units. The coarse, peloidal bioclastic grainstone at location LEC8Loc4 is cross-bedded. The crossbedding and absence of fines indicates deposition during relatively higher energy conditions. The mudstone units are strongly weathered and poorly exposed. Mudstones are often laminated and bioclastic.

5.1.2 Upper unit

The upper unit was observed in all four sections and forms the most extensive exposure in the study area. The upper unit is dominated by fossiliferous packstones with subordinate mudstone beds and mudstone partings. The basal units are typically massive medium or coarse grained bioclastic and medium grained peloidal packstone or grainstone. The beds are oyster rich with common Praeexogyra. Brachiopods Terabratula and gastropods Nerinea are also present along with echinoderm spines. Bioturbation is common. The upper part of the unit is thinly bedded medium or coarse grained bioclastic and medium to coarse grained peloidal packstone with ooids and lithic grains. Bivalves, brachiopods and gastropods Nerinea are observed but oysters are less common. The peloids observed are typically medium grained and have orange or brown coatings.

A.1.1 Overall geological assessment

The observations made during this study are compatible with previous studies in Roade Cutting. The units exposed contain many features typical of the Blisworth limestone Formation. The lithology and biofacies of the strata exposed indicates deposition in a shallow marine shelf in a warm, probably subtropical environment. This is compatible with palaeogeographic reconstructions of the region for the Middle Jurassic (Barron, Lott & Riding, 2012). The facies present suggest typically low energy conditions in which carbonate mud accumulated and a mollusc dominated fauna developed. The dominance of shell fragments, over whole shells through most of the succession indicates either energy conditions sufficiently high to break up the shells or that shell fragments were transported from higher energy environments. The presence of coarse grained bed exhibiting tabular crossbedding record periods of higher energy deposition, possibly storm events, occurred. The accumulation of oysters and brachiopods and intense reworking of sediments at the base of the upper unit suggests that sediment deposition slowed leading to the formation of hardgrounds. The presence of sand and silt within many units indicates a persistent source of clastic sediment thought to have been the London Landmass to the southeast (Barron & Woods 2010b).

5.2 Proposed correlations

The poor quality of the exposure and the lateral variation in facies typical of the Blisworth Limestone Formation makes correlation between the four localities and with previous stratigraphic schemes challenging. A correlation between the locations studies is presented in Figure 5-1 and is based primarily on the occurrence of oyster rich beds in the lower part of the upper unit which are the best exposed units.

The geological profile provided in Thompson (1924) (Figure 1-1) indicates that the exposures studied close to bridge 211 lie in the middle part of the Great Oolite Limestone (Blisworth Limestone Formation). Barron & Woods (2010b) subdivide the succession exposed between bridges 208 and 210 into six units (A-F) based on lithology and fossil assemblages. Based on their descriptions a tentative correlation is proposed (Figure 5-1). The lower unit identified in this study is dominated by packstones and mudstones that are not notably fossiliferous and contains a distinctive crossbedded grainstone, this unit is comparable with Unit E of Barron & Woods (2010b). The upper unit is limestone dominated and fossiliferous and is correlated with Unit F of Barron & Woods (2010b).


Barron & Woods (2010b) attempted to correlate their Units with the beds defined by Thompson (1924) with limited success, especially for their units E and F. The distinctive crossbedded unit is correlated with Thompsons bed 12. The overlying strata recorded in this study and by Barron & Woods (2010b) are tentatively correlated with Thompson's beds 11 and 10 (Unit E) and bed 9 (Unit F). However, there are significant differences between Thompson's observations and the more recent studies which are difficult to explain except by invoking lateral variation of strata.


Figure 5-1: Photo montage showing the localities studied and proposed correlation.


Figure 5-2: Proposed correlation between the localities studied.


6 Conclusions This report summarises the geological succession exposed on the southwest side of Roade Cutting between mileage 60.0050 and 60.1630 south of Bridge 211 (Courteenhall Road Bridge). Bedrock exposures at this location are small and strongly weathered, they are accessible only using roped access techniques. The outcrops described comprise a succession of limestones and mudstones. The exposed succession comprises fossiliferous shallow marine limestones interbedded with mudstones and is characteristic of the Blisworth Limestone Formation.

Four localities were investigated and a correlation with previous work on well exposed sections between bridges 208 and 210 is proposed. The exposed succession lies within the middle part of the Blisworth Limestone Formation and is equivalent to units E and F of Barron & Woods (2010b). A correlation with bed descriptions of Thompson (1924) is more problematic but the studied interval is likely equivalent to beds 9-12 of Thompson (1924).


References Barron, A J M, Lott, G K and Riding, J B (2012). Stratigraphical framework for the Middle Jurassic strata of Great Britain and the adjoining continental shelf. British Geological Survey Research Report, RR/11/06. 187pp.

Barron, A J M and Woods, M A (2010a). The geology of strata exposed in Roade railway cutting, Northamptonshire: engineering phases Priority 1 and 2. British Geological Survey Commissioned Report, CR/06/012. 50pp.

Barron, A J M and Woods, M A (2010b). The geology of strata exposed in Roade railway cutting, Northamptonshire: engineering phase Priority 3 sections and overall assessment. British Geological Survey Commissioned Report, OR/10/039. 37pp.

Thompson, B (1924). The geology of Roade cutting. Geological Magazine, Vol. 61, 210-218.

Woodward, H B. 1894. The Jurassic rocks of Britain. Vol. 4. The Lower Oolitic rocks of England (Yorkshire excepted). Memoir of the Geological Survey of the United Kingdom.

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LEC1 Courteenhall Phase 2 - British Geological Survey · LEC1 Courteenhall Phase 2 Geological Survey of SSSI June 2017 J Murphy & Sons Limited Wigan Road Goldborne Warrington Cheshire