Organic petrology in the 19th, 20th, and 21st centuries: The Newcastle contribution

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International Journal of Coal

Organic petrology in the 19th, 20th, and 21st centuries:

The Newcastle contribution

Duncan Murchison

School of Civil Engineering and Geosciences, University of Newcastle, Newcastle upon Tyne NE1 7RU, UK

Accepted 29 June 2004

Abstract

The paper describes the development of coal petrology, then organic petrology, over a period of approximately 175 years

around and in Newcastle upon Tyne (England). From 1833 until 1950, the basis of study was essentially transmitted light

microscopy. In this period, perhaps the supreme contribution was the work of Hutton, Lindley, andWitham, who demonstrated the

vegetable nature of coal in 1833. Amajor Scottish legal case, the dBoghead ControversyT of 1853, in which dNewcastleTwasmuch

later to be involved, was not finally resolved until Blackburn and Temperly confirmed the true nature of the relationship between

the modern alga Botryococcus and the algal coals some 80 years later. In the early part of the 20th century, works by Hickling on

the dcoal beltT and Hickling and Marshall on the cell structures of vitrinites were important as was Raistrick’s substantial

contribution to the founding of the field of palynology through his microspore correlation studies on coal seams from the coalfields

of northeast England and Lancashire.

Large-scale organisational changes in the Department of Geology at Newcastle in the period 1950 to 1989 took place

with the development of the Organic Geochemistry Unit (OGU) in which organic petrology was a major component. Organic

petrology and organic geochemistry were major components. There was almost entire replacement of transmitted light

microscopy by reflected light procedures as the principal means of studying crustal organic matter microscopically.

Widespread collaboration with industry, particularly with oil companies, which, with the University and the Research

Councils, provided invaluable support to the research group over many years. Considered here are the results of

investigations across the expanding field of organic petrology, covering the development of equipment and relationships

between maceral properties, the varied effects of carbonisation treatments, and the influence of igneous activity on crustal

organic matter.

There were further radical changes in the composition of the research group after the completion of the national Earth

Science Review in 1989. The Institute of Fossil Fuels and Environmental Geochemistry (FFEGI) was formed with a

further substantial increase of both staff and postgraduate students. Organic petrology as a component was much reduced,

although reflected light studies continued on coals from the offshore coalfields of northeast England, and transmitted

light studies, almost exclusively related to the study of organic facies, returned. The output of organic petrologists

virtually ceased. Most effective research groups, however, shift their emphases with time. FFEGI occupied a substantial

0166-5162/$ - s

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Geology 62 (2005) 5–31

ee front matter D 2004 Elsevier B.V. All rights reserved.

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ess: [email protected].

D. Murchison / International Journal of Coal Geology 62 (2005) 5–316

and successful international research niche within the environmental field, as well as being still heavily committed to

petroleum geochemistry until 2003 when FFEGI was integrated within the new School of Civil Engineering and

Geosciences.

D 2004 Elsevier B.V. All rights reserved.

Keywords: Early research in organic petrology; Newcastle; Organic Geochemistry Unit; Institute of Fossil Fuels and Environmental

Geochemistry; School of Civil Engineering and Geosciences

1. Introduction

This paper is intended as a recognition, on the

occasion of this Festschrift, of the important and

extensive scientific contribution that Marlies

Teichmqller made to the field of organic petrology.

She was also partly responsible for the bNewcastlecontributionQ because of continued contact with the

research group over many years. There is now a

hiatus in organic petrological research and teaching

at Newcastle—surely only temporary. This hiatus is

as good an opportunity as any to consider how

bNewcastle,Q through the efforts of many, has

contributed to the growth of coal petrology, then

organic petrology, over a period of approximately

175 years.

Those reading this paper may associate coal and

organic petrology and bNewcastleQ solely with the

University of Newcastle. That association would be

correct in recent times. Prior to 1963, however, the

association was with King’s College and before that

with Armstrong College, both constituent parts of

the University of Durham, although both were

located in Newcastle upon Tyne. But the start of

the microscopical study of crustal organic matter in

Newcastle in the early 19th century was strictly

confined to coals and did not take place within

learned institutions, but elsewhere, and by others

employed in different fields (e.g., in insurance and

mine surveying). In its earlier context, the term

bNewcastleQ covers not only the city in the modern

strict sense, but an area with a radius of perhaps 30

km from the modern city centre. Announcements of

major advances in the field in the early days were

usually punctuated by years of seemingly complete

inactivity.

Some of the earlier material in this paper has

already formed part of a Presidential Address to the

Royal Microscopical Society (Murchison, 1979).

That part of the current contribution, while necessa-

rily having a similar underlying historical basis, is

considerably extended and has a rather different

focus. And although this paper is based on organic

petrological research over the years in Newcastle,

organic geochemistry should not be forgotten, even

if the bNewcastleQ contribution to this field is hardly

recorded here. Close integration of organic petrology

and organic geochemistry is sometimes difficult but

certainly seems easier when considering organic

deposits from terrestrial/lacustrine environments

rather than from marine environments (e.g., see an

overview by Murchison, 1987 on doil from coalT).

2. The years 1830–1900

dVarious authorities agreed that in the year 1833,

three Englishmen were the first to apply the micro-

scope to the investigation of coalT (Stopes and

Wheeler, 1918). They were William Hutton, John

Lindley, and Henry Witham, who raised the under-

standing of the origin of coal and its microstructure

immensely. While John Lindley was a dprofessional,Tin that he was at the time a professor of botany,

Henry Witham of Lartington Hall was strictly an

enthusiastic and effective collector of fossil plants

who wrote innumerable papers describing them.

William Hutton was a friend of Witham and an

insurance agent. He was a shrewd field observer and

published many accounts of his geological observa-

tions, mainly in the English counties of Northumber-

land and Durham.

Hutton and Witham were both from Newcastle.

Witham it was who first obtained in 1832, and then

described (Witham, 1835), the sections of coals,

principally from the Northumberland and Durham

coalfields, which were most probably prepared at

that time by an Edinburgh lapidary called Sanderson,

D. Murchison / International Journal of Coal Geology 62 (2005) 5–31 7

a task requiring great skill. In that same year, Hutton,

having had the opportunity to examine Witham’s

sections, read a paper entitled dObservations on

CoalT to the Geological Society of London, which

was later published (Hutton, 1833, 1834). The then

President of the Society, Roderick Impey Murchison,

in his Presidential Address for 1833, stated, bIt hasbeen reserved to Mr. Hutton. . . to complete the

solution of the problem of demonstrating the vegetable

structure in coal itselfQ (Murchison, 1834). Although

based on an erroneous interpretation of bubbles in the

thin sections, due to the way they had been prepared,

Murchison also stressed the practical value of Hutton’s

work in suggesting sources of gases in coals, which

were the cause of disastrous explosions in collieries of

the times.

The preparation and subsequent analysis of these

coal sections represented an early major advance in

coal petrology, which has expanded into what is now

the field of organic petrology. In modern times,

photomicrographs of the sections would have been

published and indeed they were, more than 100 years

after their preparation, in an analysis of Hutton’s paper

by Hickling (1936). In 1833, without the technical

advantages of photomicrography, illustrations of the

sections could only be made by drawings or paintings.

A London artist, T.A. Prior, was commissioned to

reproduce the appearance of the sections at dhighmagnificationT (in reality �20). These excellent

miniature water colours are now preserved in the

Hancock Museum in Newcastle upon Tyne.

For the remainder of the century, no further

contribution to the field emanated from Newcastle.

Indeed, there was little significant microscopical

activity in the field of coal in the UK until 1900,

although papers on the microscopy of coal were

published abroad. Only one event, in mid-19th

century Britain, gave a temporary stimulation and

resurgence to the microscopical examination of coals.

The dBoghead ControversyT was a major trial (Lyell,

1853), located in Edinburgh, the basis of which was to

decide whether or not the so-called dTorbanehillmineralT was coal or mineral. Although dNewcastleTwas not directly involved in the trial, final resolution

of the precise nature of torbanite was not achieved

until the studies of Blackburn and Temperly, working

in Newcastle, were published in 1936 and on which

there is further comment later in this paper.

3. The years 1900–1950

3.1. The nature of coal

Within coal petrology in the UK, the first 50 years of

the 20th century were dominated by three personalities:

George Hickling, Clarence Seyler, and Marie Stopes.

Of these, only Hickling had trained as a geologist:

Stopes was a botanist and Seyler was a chemist by

initial training. Hickling felt—and occasionally said

so—that the lack of a geological training left both

Seyler and Stopes at a disadvantage in at least some of

the interpretations necessary in elucidating the nature

of coals. Apparently neither Seyler nor Stopes felt such

a disadvantage and both expressed their views firmly

on the nature of coal to one another and to wider

audiences over the many years they were in contact.

Hickling came to Armstrong College (University

of Durham), situated in Newcastle upon Tyne, in

1920. Before this appointment, he had been a member

of staff in the University of Manchester from 1906.

During his time there, much of his work lay outside of

coal science in the strict sense. Palaeobotany was a

strong interest, but so also was more general geology,

ranging from footprints in Permian sediments, through

the origin of China clay, to the mapping of Old Red

Sandstone rocks; in particular, structural problems

within the Coal Measures interested him. Hickling’s

principal contributions to coal petrology lay in two

areas. First, stemming from his earliest work on fossil

plants, he had an abiding interest in the palae-

obotanical nature of coal constituents: thus, much of

his professional life was spent studying coal as a

material. His second contribution lay in his clear

understanding of the difference between dtypeT and

drankT and the implications that both of these concepts

had for coal composition and behaviour.

By the time Hickling arrived in Newcastle, he

already had well-formed views on the nature of coal. In

Manchester, he had built up this picture through the use

of thin sections made by E.T. Newton for Huxley

(1870), and then later using sections made in the early

years of the 20th century by Lomax (1911), who was

concerned with the use of microscopy in applied

aspects of the subject. Hickling (1916, 1917) published

his work in two papers, the first of which concentrated

principally on the nature of the substance, which was, a

few years later, to be termed dvitrainT by Stopes (1919).


The second paper went further, recognising first that

each separate lenticle of dbright coalT was part of a

continuous fragment of plant tissue; second, that bark

was a more common contributor to coals than wood;

and, third, that, besides dbright coal,T there were also

ddull coalT layers, which were variable in composition,

containing, as they did, spores, cuticles, resins, and

other components.

Hickling continued his research on the fundamental

nature of coal after coming to Newcastle, particularly in

collaboration with Charles Marshall. Using the thin

black bands of vitrinite (Stopes, 1935) found in shales

overlying coal seams, Hickling andMarshall employed

microscopical examination to relate the cell structures

in their thin sections to the original surface ornamenta-

tion impressed on the surfaces of the vitrinite bands or

on the shales enclosing the vitrinites. Through this

procedure, they identified five important sources of

vitrinite in Carboniferous coals: three different barks of

the Lycopods (Bothrodendra, Lepidodendra and Sigil-

laria), and wood related to Cordaites and to the

Cycadophytes. Their work was published in two papers

(Hickling and Marshall, 1932, 1933). Although con-

cern was expressed in later times of the dangers of

making such highly specific correlations between cell

structures and the external ornamentation of particular

plants, and applying them widely, there is no question

that the work of these authors led to a greater under-

standing of the nature of coal constitution, not just of

the vitrinite-rich black dbright coalsT (the dclarainsT ofStopes, 1919), but also of the microclastic coals, the

ddurainsT of Stopes (1919), and the cannel coals.

Even more significant was Hickling’s clear under-

standing that the properties of coals were not only

governed by the then familiar concept of drankT—the

modification of coal properties in one direction by the

geological circumstances to which the deposits had

been exposed through time—but also by dtype.TAlthough not the first to recognise the importance of

biochemical influences in the early development of

coals (e.g., see White, 1908), Hickling emphasised

that differences between coals were strongly governed

by their earliest history, namely the differences

between the vegetable constitutions of the deposits

laid down in the coal swamps and also by the varying

degrees of exposure the accumulations received

through a variety of influences (oxidation, acidity/

alkalinity, microbial activity, etc.), during what is now

termed the dbiochemical stage of coalification.T In one

of his most influential papers, dThe Properties of

Coals as Determined by Their Mode of Origin,THickling (1932) introduced the term dtypeT to describe

the variability between coals arising from their

differing vegetable compositions. The importance of

dtypeT was little acknowledged by coal scientists at

this time. Only later did dtypeT become as important as

drankT in understanding the properties and the variable

behaviour of coals. (But there is no doubt that

Plettner, 1852 revived a suggestion made by Hutton,

1833 that differences between coals depended on

differences in the materials composing them.)

In his paper of 1932, Hickling’s capacity for lucidity

and rendering in simple terms what might appear

complicated, if communicated by others, is well

demonstrated. Using a series of diagrams, he showed

on a carbon/oxygen plot that the analyses of more than

1200 coals lay in a narrow belt—the dcoal belt,T whichextended from peat to anthracite and exemplified drankT(Fig. 1) On similar diagrams, he demonstrated by the

use of carbon/oxygen plots for single seams that the

plots fell on straight lines for each seam (dseamcurvesT), which were parallel to each other within the

limits of the dcoal belt.T Similar plots for cannel coals

and torbanites maintained this same parallelism, but the

seam curves for these deposits lay outside of the limits

of the dcoal belt.T Each curve represented progressive

changes in rank for a particular seam. The different

positions of the parallel curves, both within and outside

of the coal belt, were simply a reflection of differences

in the hydrogen contents of the accumulations,

controlled by the varying vegetable compositions

(dpetrographic compositionsT) of the deposits, namely

their dtypeT (Fig. 2). For each seam, the petrographic

composition varied little from point to point: the

petrographic contrasts were between seams.

3.2. Spore studies

Working alongside Hickling and Marshall at this

time were others who contributed substantially to coal

petrology: foremost among these was Arthur Rais-

trick. Raistrick was a geologist with wide interests

who spent the greater part of his working life in the

Department of Geology at Newcastle. In the mid- to

late-1920s, Raistrick became interested in peat pollen

analysis and its possible use in the correlation of peat

Fig. 1. The bcoal beltQ, based on Hickling (1927), indicating the range of approximate composition in terms of carbon, oxygen and hydrogen of

different ranks of coal. The lines of hydrogen content, running roughly parallel to the bcoal beltQ, reflect dtypeT of coal (modified and redrawn from

Raistrick and Marshall, 1939).


deposits. It was but a short step to considering the use of

miospores in coals for the same purpose. At that time,

the problems of anything other than quite broad

correlations within the rocks of the Coal Measures

and similar sedimentary successions were well known

and highly frustrating to geologists. Smith and Butter-

worth (1967), unimpeachable sources, state,

bAlthough an attempt to classify the various types of

miospores present in coal. . . was made by Evans

(1925–1926). . . Raistrick may properly be regarded as

the first investigator in this country to study them

systematically and to use them for the purposes of

seam correlation.QCarboniferous coals contain abundant miospores,

especially microspores, which can be isolated by

oxidising ground coal with Schultz’s solution (two

parts of concentrated nitric acid and one part of a

saturated solution of potassium chlorate). The resulting

mixture of freed, resistant microspores can then be

cleaned and mounted for microscopical examination

when the different spore types can be identified and

counted, and their proportions calculated. Two assump-

tions were inherent to the reliability of the method.

First, the microspores, in large quantities, would have

been primarily distributed by wind and, because of

their small size and low density, were capable of being

carried for great distances. They would be mixed and

blown about so that a uniform scatter was obtained. At

most localities, a statistical average of the spores

produced by the forests of the time could be expected.

The second assumption was that because of evolu-

tionary trends, the composition of the flora of

successive coal-forming swamps would alter suffi-

ciently to ensure that there would be a different

proportionality detectable in the spore averages.

Using these assumptions, Raistrick set about pro-

ducing histograms for spore proportions of coals in

vertical sections at different localities. A single seam

would be expected to give spore proportion diagrams

with similar patterns at different localities (Fig. 3).

Unknown isolated coal samples with the same pattern

could then be fitted into the correlation. Seams above

and below would have sufficiently different patterns to

allow a general correlation to be projected across a

Fig. 3. Method of correlating the microspore diagrams of two series

of seams, A and D, with those of known successions of seams B and

C (modified and redrawn from Raistrick and Marshall, 1939).

Fig. 2. Curves, based on carbon and oxygen contents, for coals of

three seams lying within the bcoal beltQ. Separation between the

seam curves reflects the differing levels of hydrogen content of

samples from the three seams (modified and redrawn from Raistrick

and Marshall, 1939).


coalfield. Were there insufficient differences between

dgeneralT spore patterns of seams above and below one

another in a succession, use could also be made of

diagrams based on daccessoryT spores, most of which

had a much restricted vertical range.

The pioneering work of Raistrick, published in four

principal papers (Raistrick and Simpson, 1932–1933;

Raistrick, 1934–1935, 1936–1937, 1938–1939),

stimulated the interest of other workers. Miospore

studies in many of the British coalfields soon followed.

By the time a further 25 years or so had passed, Smith

and Butterworth, both of whom became foremost

workers on spores internationally, were able to compile

the signal volume, the dMiospores in the Coal Seams of

the Carboniferous of Great BritainT (1967). Within the

volume, they published a critique of Raistrick’s work,

which, while recognising it had great potential value in

improving correlation of coal seams, did show weak-

nesses in the dgeneralT spore diagrams. They were also

critical of the arbitrary system of spore classification

that Raistrick had devised and which was eventually

replaced by a binomial system of nomenclature. One

final point should be noted. At the time of Raistrick’s

work, miospore studies were a part of coal petrology.

By 1967, miospore studies of coals and sediments had

expanded to such a degree that they had become

separated from coal petrology and now lay in the newer

field of palynology.

3.3. Algal studies

Earlier in this paper there was a brief reference to a

major trial that took place in Edinburgh in 1853, which

was concerned with the nature of a deposit at

Torbanehill lying some 20 km to the west of the city

of Edinburgh in Scotland. At the trial, 78 professional

witnesses were called—33 for the plaintiff and 45 for

the defendant. Many of the witnesses were directly

connected with the medical profession because of their

experience with and their ownership of microscopes.

Acrimony was widespread at the trial between the law

and the scientific witnesses. Quekett (1854) published

a long account of the proceedings at the trial, including

a transcription of the examination and cross-examina-

tion of the professional witnesses on microscopy. He

had his competency called into question by the judge

because he was not a botanist and so, bnot, as I

understand, conversant or skillful in fossil plants.Q TheRoyal Microscopical Society, of which Quekett later

became President, was described by the judge to the

jury as ba learned body who make it their object to pry

into all things.Q

Fig. 4. Transverse, longitudinal and perspective diagrams o

Botryococcus braunii illustrating the development of cup structure

(a–c) first, second and third cups, respectively; (d) cell; (e) space

between cups (from B.N. Temperly) (redrawn by permission of the

Royal Society of Edinburgh from Transactions of the Royal Society

of Edinburgh, 58 (1933–1936), pp. 841–868).


While such intemperate legal commentary might

perhaps have been expected in the immediate hot-

house of such an important issue of the time, those

involved in the trial might have been surprised to

realise that more than 80 years would pass before the

nature of the dTorbanehill mineralT was finally

resolved. The scientific controversy surrounded the

true character of the dalgaeT in the deposit. An

extensive literature developed around the nature of

these bodies. Many writers claimed that the dalgaeTwere no more than decomposed spores. Others were

firmly convinced that the true nature of the Torbane-

hill deposit—and many other similar deposits that

came to light over the years—was algal.

The problem was finally solved when Blackburn

and Temperly (1933–1936)—Blackburn a botanist

and Temperly a geologist—made thorough investiga-

tions of the modern fat-secreting, planktonic, green

alga, Botryococcus braunii Kutzing. This alga forms

polymorphous colonies, is a widely distributed inhab-

itant of freshwater lakes and lagoons throughout the

world, and is seemingly content to live under both

temperate and tropical conditions. The individuals live

in pear-shaped cells with thick stratified walls, in

groups of four (Fig. 4), sometimes connected by

transparent filaments, particularly in the larger colo-

nies. The cell membranes secrete oil and the colonies

are gelatinous, so they are thus able to float. In some

parts of the world, B. braunii is so abundant that it

forms combustible deposits (e.g., dcoorongiteT in the

Coroong of South Australia and dbalkashiteT in Lake

Balkash in Russia).

Blackburn and Temperly demonstrated that B.

braunii was identical to the fossil alga Pila, which is

concentrated in Scottish and French Palaeozoic torban-

ites. Accompanying Pila in the Scottish torbanites is

the less frequently occurring (in coals) alga Reinschia,

which can also be compared with Botryococcus.

Reinschia occurs as a hollow sphere in horizontal

sections, but, when cut vertically, frequently appears

compressed, with the cavity appearing as a straight line.

Reinschia can be distinguished micropetrographically

from Pila, which may display a chrysanthemum-like

appearance, but is also often compressed. Blackburn

and Temperly’s work virtually settled the long-running

dispute over the origin and relationships of the two

Carboniferous algae Pila and Reinschia. Develop-

ments in microscope fluorometry from the 1960s

f

:

onwards were to show that algae in sediments were

much more widespread and variable in character than

had ever been envisaged earlier in the century.

3.4. Carbonisation and X-ray diffraction

There was virtual cessation of coal petrological

research at Newcastle between 1940 and 1950,

principally due to the Second World War and its

aftermath. Although not petrological, a notable piece

of work on the molecular–structural changes in coals

of different rank carbonised up to a temperature of

1750 8C was published by Blayden et al. (1944),

working in the Northern Coke Research Laboratories

of the Department of Chemistry at Newcastle. The

molecular changes were followed by tracing the paths

of three well-known parameters from the carbonized

coals by X-ray diffraction procedures:

Lc, which estimates the heights of stacks of

aromatic layers


La, which estimates the diameters of stacks of

aromatic layers

d, which estimates the average spacing of the

aromatic layers.

The values obtained for these parameters are, of

course, daveragesT for the carbonized dwhole coals,Tnot for individual macerals as they would be today.

The results of this work (Fig. 5) were to prove

useful some 30 years later in the interpretation of

fundamental optical changes observed in a variety of

sedimentary organic matter carbonised in the New-

castle laboratories. The results of Franklin (1951)

and Diamond (1960) did not affect the interpreta-

tions of the earlier Newcastle X-ray studies in any

significant way qualitatively, although the numerical

values of the three parameters were altered by the

later work.

Fig. 5. Variation with temperature of the heights (Lc) and the diamete

Northumberland coal (daf carbon 81.7%), low-volatile bituminous Durham

(from Blayden et al., 1944).

4. The years 1950–1989

4.1. Organic Geochemistry Unit (OGU), University of

Newcastle

A paper, again not petrological, but one which

would also have a strong influence on organic

petrological research some years later, rather like the

earlier paper on X-ray studies of carbonized coals by

Blayden et al. (1944), was published by Hickling

(1949–1950). Despite considerable skepticism

expressed by others, Hickling argued persuasively

that the sinking of boreholes offshore of the North-

umberland and Durham coalfields would reveal

plentiful coal reserves. The National Coal Board

(NCB), and later British Coal, carried out an

exploratory programme from 1958 to 1985, which

saw 103 boreholes sunk over an area of approximately

rs (La) of the aromatic layer groups of high-volatile bituminous

coal (daf carbon 88.4%), and Welsh anthracite (daf carbon 92.5%)


900 km2, extending up to 15 km from the coastline

(Fig. 6). Relatively little petrological work on the

large numbers of coals produced was published until

late in the programme. Some of this work will be

discussed later but much remains to appear. Despite

his commitment to the use of transmitted light in

organic petrology, Hickling (1952) also acknowl-

edged that the use of reflected light was an entirely

effective method for the study of coals.

Over the period 1950–1989, organic petrological

research at Newcastle was concentrated into four

principal areas, three of which ultimately accounted

for perhaps 80% of published work. A limited

Fig. 6. Positions of boreholes sunk during the offshore drilling program in t

the National Coal Board and British Coal over the period 1958–1985 (re

Elsevier).

summary of this kind, however, can do no more than

suggest the ways in which the many involved over

these years contributed to the work of the research

group:

! In the early part of the period, there was much

emphasis, as there was elsewhere, on the relation-

ships between the optical and chemical properties

of coal macerals. Supported by the NCB, much of

the Newcastle research was carried out, not on

standard-sized coal samples, but on dmicroTsamples

of individual macerals isolated from coals. Micro-

scopical equipment suitable for coal research but

he northeast of England (Northumberland and Durham coalfields) by

printed from Pearson and Murchison, 1999, with permission from


applicable in other fields, notably on radioactive

minerals and sinters, was also developed.

! The effects of carbonisation and oxidation, some-

times combined, upon the optical properties of

organic matter, particularly vitrinite and bitumens,

was also an area of extended research. Support for

this work came from the Research Councils, and

carbonisation and steel industries. Some of this

work was fundamental, some applied, but much of

it had likely implications in the support of the third

area of organic petrological research.

! There had been long-standing interest at Newcastle

on the effects of igneous activity upon crustal

organic matter. Modern organic petrological

research in this area extended from the 1930s, but

papers on the topic (field observations on coals) had

even appeared in the early 19th century. Some of the

laboratory work on carbonisation related well to the

data obtained from igneous-affected surface and

borehole samples and helped in interpretations.

Again the Research Councils supported much of

this work with financial aid, which also came from

other sources such as the oil industry.

! Many oil companies required organic petrographic

data (principally reflectance measurements to

establish maturation levels) that were occasionally

also related to organic geochemical parameters

from well samples worldwide. While most of these

results remain unpublished, the symbiotic relation-

ships between the oil companies and the Newcastle

research group again provided funding to support

organic petrology.

In 1964, organic petrology, incorporating organic

matter of sediments as well as coal petrology, was

well settled within the new OGU in the Department of

Geology at Newcastle. The University, the Depart-

ment of Scientific and Industrial Research (forerunner

of the Research Councils), and British Petroleum were

responsible for funding the formation of the new Unit.

The OGU remained in this form until the Earth

Science Review of 1989 imposed a major reorganiza-

tion of the Earth sciences in universities throughout

the UK. A substantial impetus to the early work of the

OGU was given by the contributions to the 13th Inter-

University Geological Congress held in the University

of Newcastle at the beginning of 1965. The title of the

congress was dCoal and Coal-Bearing Strata,T the

contributions from which were brought together in a

research textbook (Murchison and Westoll, 1968) of

the same name. The success of the congress depended

much on the German workers, who attended in force,

notable among them being Marlies and Rolf

Teichmqller who presented two major contributions.

4.2. Development of equipment and the assessment of

properties of coals and macerals

In the period prior to the setting up of the OGU in

1964, the Extra-Mural Department of the NCB was

the primary provider of external grants to the Depart-

ment of Geology for coal research. There was

considerable interest on the part of the Board in the

properties of coals and their constituents, particularly

since the NCB was the main provider of coal for use

in the British steel industry. The position was similar

to that in all industrial countries and many laboratories

were occupied in this area of research. Amassing

quantities of the different macerals for varying forms

of analysis under national norms was a substantial

(and dirty) operation, which was more suited to

industrial-scale grinding and separating equipment,

far beyond the scale desirable or even possible in

university research laboratories.

The decision was made at Newcastle to operate on a

dmicroscaleT and to develop separating methods, which

would yield quantities of macerals suitable for micro-

analysis, except in the case of some vitrinite, which,

because of its mode of occurrence in bands, was less of

a separation challenge than were other macerals. Early

in this period, Jones (1961a) designed a method of

separation of macerals in ground coals, using a graded

density column formed from a solution of potassium

mercuric iodide, in which graded ranges of specific

gravity could be adjusted to the likely densities of the

macerals in any coal. The separations were more

amenable to physical study, rather than to chemical

analysis, because of the problem of bstickingQ of theseparating liquid to the finely ground macerals. As an

alternative to the graded density column, almost an

doakum-pickingT procedure was developed using finelyground surfaces on coal blocks under a binocular

microscope to collect appropriate macerals (e.g.,

megaspores and globules and bands of resinite for

microscale chemical analysis, reflectance measure-

ment, and infrared analysis). Although the quantities


obtained were small, in most instances their purities

were high. Jones (1961b) also devised an effective

method for determining the densities of macerals

collected on these small scales. When suitable samples

of coals were unavailable from the NCB, coal cores

could be obtained from depths to approximately 100 m

using a small-scale drilling rig (Farmer et al., 1968). If

block samples or large cores were available from the

NCB, they were cored to a convenient size using

equipment designed by Jones and Bell (1963). These

technical developments were essential for the success-

ful advance of the research programs of the time, as was

the assessment of the quality of polished surfaces of

macerals (Murchison and Boult, 1961) and modifica-

tion of infrared procedures to study maceral spectra

(Crawford et al., 1960).

As a result of these separation procedures, a

number of papers soon appeared on the properties of

resinites in coals (Murchison, 1963, 1966; Jones and

Murchison, 1963; Murchison and Jones, 1963, 1964).

There was a widespread acceptance among organic

petrologists at this time that property differences

between macerals were of degree, rather than anything

more radical, but the data produced showed without

question that resinites differed markedly from spor-

inites—the most widely investigated of the liptinitic

macerals. The Newcastle studies also confirmed that

there were pronounced differences between the resin-

ites of brown coals and bituminous coals. And

although work elsewhere had shown that alginites

were dhigh-hydrogenT components of the deposits in

which they occurred, their properties were more

firmly delineated by Millais and Murchison (1969),

thus substantiating the wide spread of properties

within the liptinite group of macerals.

Cooper and Murchison (1971) also demonstrated,

using plots of atomic ratios (H/C:O/C), that spore-rich

exinites (liptinites) from the Lorraine coalfield (limnic

with perhydrous coals) differed compositionally from

spore-rich exinites of the paralic coalfields of the Ruhr

and the UK. Causes of the differences lay possibly in

groundwater chemistry or in contrasting coalification/

tectonic histories. The varying properties of the

liptinite group were partly at the root of the challenge

(Cooper and Murchison, 1970) to the contention that

there was a low-temperature process degrading the

organic matter of shales to leave a residue of aliphatic-

based kerogen, the dsporopolleninT of Brooks and

Shaw (1968). Although the amounts in any coal

would generally be small, many sporinites were

altered to varying degrees during the biochemical

stage of coalification—some vitrinised, some fusi-

nised—with all intermediate variations (Stach, 1962;

Bell and Murchison, 1966). These considerable

alterations contributed to the variability of the proper-

ties of the concentrates in some cases.

Compositional differences between the liptinitic

macerals were emphasised many years later when the

order of generation of petroleum hydrocarbons from

different liptinites with rising thermal maturity was

clearly demonstrated (Khavari-Khorasani and Murch-

ison, 1988). Fluorescence microscopy was applied to

liptinitic samples from essentially a single sedimen-

tary basin. The liptinite emission spectra show clearly

that the hydrogen-generating capacities of the differ-

ent liptinite macerals attain their maxima at different

maturity levels. The major shift of the spectral

maxima towards the red for each maceral almost

certainly corresponds to the time of expulsion of

dexsudatiniteT (Teichmuller, 1974). Exsudatinite is a

secondary maceral related to petroleum, and was

discussed by Murchison (1976), with particular

reference to expulsion from several liptinitic macerals,

particularly resinite, at maturity levels immediately

prior to the time of maximum petroleum generation.

In the early 1960s, the development of appropriate

microscope photometry systems to allow the measure-

ment of reflectance on small areas (b5 Am diameter)

had hardly passed its infancy. Reflectance measure-

ment within the OGU was greatly helped by the

construction of a microphotometer system by Jones

(1962). The Atomic Energy Authority then asked the

research group to devise a photometer system to allow

the reflectance measurement of radioactive materials,

particularly uranium oxide sinters, to determine their

oxygen/metal ratios. That investigation was largely

successful (Jones and Murchison, 1965), after Jones

succeeded in partially replicating part of a photometer

system, produced by Gabler et al. (1960), the whole of

which was then installed in a glove box (Jones et al.,

1968). Although more tedious to use than modern

conventional photometer systems, the installed photo-

meter was not only suitable for work on radioactive

materials, but also for measurements on samples

requiring the protection of an inert atmosphere. The

photometer construction assisted future studies, par-


ticularly those on dispersed organic matter in sedi-

ments, and in establishing the then largely unrealised,

or at least unreported, widespread biaxicity of

vitrinites (e.g., see Cook et al., 1972a,b; Jones et al.,

1973).

4.3. Optical studies of carbonised macerals and

bitumens

Besides the need to understand more thoroughly

the composition of coal macerals and their techno-

logical behaviour under different conditions, the

demand for steel after the Second World War was

a great stimulus to expanding knowledge about the

carbonisation process and improving its efficiency.

With the decline, due to high usage, in the

availability of single-seam coals, which would

produce high-grade metallurgical cokes on carbon-

isation, it became imperative to produce such cokes

from blends of coals, coals which, when carbonised

singly, would only yield cokes of inferior quality.

The development of prediction systems to estimate

coke stability or strength (the most crucial parameter)

from carbonised blends became essential. Earliest in

the field were the Russian workers (Ammosov et al.,

1957), followed soon afterwards by the Americans

(Schapiro et al., 1961). Over the following years,

other prediction systems were developed by steel

companies, coking agencies, and large industrial

research laboratories.

The large scale of operation of this industrially

oriented, applied research was unsuited to develop-

mental thoughts in the OGU at Newcastle. Two

further factors were important in excluding research

in this area. First, the Northern Coke (later changed to

dCarbonT in the mid-seventies) Research Laboratories

(NCRL), established in 1926 in the Department of

Chemistry of Armstrong College (University of

Durham), seemed to be a more suitable base for

research channelled towards industrial carbonisation.

Second, by the early 1960s, although coal and coke

were still important to the industrial effectiveness of

the UK, oil and gas exploration and exploitation were

becoming increasingly important to the UK’s econ-

omy. With potential staff and postgraduate students

for the OGU principally having geological back-

grounds, the doil and gasT sector seemed likely to be

more fruitful for research training and contracts.

Nevertheless, in areas in which there were oil

company interests onshore at this time, for example,

in the northeast of England and in the Midland Valley

of Scotland, igneous activity had been extensive. If

successful collaborative ventures with the oil industry

were to be joined in these areas, there was a need to

understand the responses of crustal organic matter to

igneous activity. An extensive laboratory carbon-

isation programme was set up and ran for approx-

imately 10 years in the OGU.

Vitrinite was the maceral principally involved in

the experiments, but so also were the liptinite

macerals and a range of bitumens. Understandably,

at the core of the experiments were the optical

responses of these different macerals to rising temper-

ature. But in the Newcastle experiments, in an attempt

to approach at least partially the consequences of

igneous activity in the natural environment, appro-

priate variations to the carbonisation conditions were

imposed, as were modifications, such as oxidation, to

the constituents prior to heating. An overview of some

of this work is given by Murchison (1978) and

summarised with the results of later work in Murch-

ison (1991), but described in more detail in Goodarzi

and Murchison (1972, 1973, 1976a, 1977, 1978).

The general behaviour of the properties of the

macerals in response to moderate rise of temperature

in an inert environment was generally well understood

at this time. All the macerals, with the exception of

those in the highest-rank coals and many of those in

the inertinite group, react similarly optically, but at

different rates, at least up to a temperature of 1000 8C.Above this temperature, behaviour is less regular

(Goodarzi, 1984). In the lower-rank macerals, the

onset of plasticity, resolidification, and molecular

reorganisation in the solid can be clearly identified

in the paths of changing optical properties with rising

temperature (Fig. 7). What is surprising is that when

anthracites are carbonised, even to temperatures in

excess of 2000 8C, remnant plant cell structures may

be retained in the resulting carbons (Goodarzi and

Murchison, 1988). Indeed, occasionally, such struc-

tures can be seen in carbonised lower-rank vitrinites,

which have passed through fluidity and developed a

mosaic (Goodarzi and Murchison, 1976b). Jones and

Creaney (1977) report similar phenomena in highly

metamorphosed vitrinites of %Roil=5.00, but without

mosaics.

Fig. 7. Variation with temperature at 546 nm of air and oil reflectances, refractive and absorptive indices of vitrinite in low-rank bituminous coal

(daf carbon 82.5%), carbonised at intervals of 50 8C between 100 and 300 8C and intervals of 25 8C over the range 300–950 8C: Ts–onset ofplasticity; Tr–onset of resolidification; Tm–onset of molecular reorganisation in the solid (reprinted from Goodarzi and Murchison, 1972, with

permission from Elsevier).


Markedly varying the heating rate of carbonisation

upwards from the customary low values of 2–3 8C/min produces pronounced changes (Fig. 8) (Goodarzi

and Murchison, 1978). So-called dnon-softeningTvitrinites clearly soften and develop distinct aniso-

tropy at high heating rates, conditions which would

certainly be met in the natural environment near to

igneous bodies. With extended residence times (6

months or more), temperatures well below those

required to cause softening of appropriate vitrinites

at conventional carbonisation temperatures will pro-

duce gas vacuoles in these vitrinites, which have also

clearly softened, accompanied by development of

strong anisotropy with a well-formed mosaic. If the

vitrinites were oxidised prior to heat treatment—again

a real possibility in the natural environment before

rapid heating by intrusions—no mosaic will form, but

both reflectance and anisotropy may be substantially

Fig. 8. Effect of varying heating rate upon the oil bireflectances (degree of anisotropy) at 546 nm of six vitrinites carbonised at intervals of 50 8Cbetween 100 and 300 8C and at intervals of 25 8C over the range 300–950 8C (reprinted from Goodarzi and Murchison, 1978, with permission

from Elsevier).

Vitrinite %Roil (max)

———— 0.67

- - - - - - 1.08

––––– 1.24. . . . . . 1.55. . - . . - . . 3.11. - . - . - . 4.11


increased. Thus, while there is no evidence of

softening, considerable molecular reordering must

have occurred in the solid. Goodarzi and Marsh

(1980a,b) confirm that preoxidation prior to carbon-

isation under pressure stabilises any inherent aniso-

tropy possessed by the vitrinites in the same way as

preoxidation alters vitrinites carbonized under normal

pressures (Goodarzi and Murchison, 1973). Increased

pressure may affect carbonized products. Goodarzi

(1985) showed that cokes from vitrinites of coking

rank carbonised under pressure develop larger

mosaics than the same cokes carbonised at atmos-

pheric pressure: they also develop higher reflectances.

Much of the work carried out by the NCRL was

heavily supported by the steel and coking industries

and did not necessarily depend upon light micro-

scopical examination; but a significant amount did

and involved the interest of both research groups.

Several geologists, with their background of trans-

mitted light microscopy at undergraduate level, and

then in reflected light microscopy as postgraduate

students in the OGU, later moved to the NCRL and

were contributors to aspects of this group’s work. At

this time, within the carbonisation field, there was a

focus on the development of nematic liquid crystals

(dmesophaseT) under different conditions of carbon-

isation. Awide range of materials was employed (e.g.,

single coals, individual macerals, pitches, and resins),

as well as co-carbonisations of these materials to-

gether with, for example, solvent-refined coals, coal

extracts, and organic additives. With these variants,

there was potential for an enormous literature to

develop from the results and it did. But within the

context of organic petrology, the development of

anisotropy within carbonised products—for that is

what mesophase development ultimately leads to—is


a restricted, albeit an important, field. Many of the

large number of publications on anisotropic carbon

over the past four decades have at their base the

excellent work of Taylor (1961) and Brooks and

Taylor (1965a,b), who clearly described the formation

of graphitising low-temperature carbons by solid-

ification from a liquid phase through the separation of

a mesophase. Marsh and Smith (1978), Marsh and

Walker (1979), and Forrest et al. (1984) review much

of the work carried out on anisotropic carbon during

these times, including that by the NCRL.

Although the most widely used property in organic

petrology, reflectance is not a fundamental parameter

of materials. Not only does its value depend upon the

refractive index and absorption index (or absorption

coefficient) of the material concerned—the value is

also governed by the refractive index of the medium in

which the reflectance measurement is made, as well as

by the wavelength of measurement. There was interest

in how the two fundamental parameters of refractive

index and absorption index (or coefficient) interrelated

as they altered with rank and carbonization temper-

ature, as well as in their precision and accuracy (Cook

and Murchison, 1977). An early comment by Huntjens

and van Krevelen (1954) demonstrated that in lower-

rank coals, the refractive index of vitrinite was the

principal cause of its reflectance rise with increasing

rank, but that beyond the coking coal level of rank,

absorption index became the dominant factor. In

carbonization experiments at Newcastle, refractive

indices and absorption indices were derived from

reflectances of vitrinites carbonised up to temperatures

of 950 8C (Goodarzi and Murchison, 1972). The

pattern of refractive index variation was similar for

vitrinites of all rank levels, rising to a peak at around

650 8C, then falling away rapidly in all cases, while

absorption index, after a slow start, rose strongly

throughout, a result that broadly followed the pattern

suggested by Huntjens and van Krevelen (1954) for

dnormalT coals. If the carbonisation conditions were

changed, while the general pattern of variation of the

derived parameters was similar, values and trends of

both refractive index and absorption index could alter

considerably, particularly with heating rate variations.

When the data for vitrinites of dnormalT coals of threegroups of authors (Huntjens and van Krevelen, 1954;

Broadbent and Shaw, 1955; Murchison, 1958) were

amalgamated and plotted (Murchison, 1963–1964),

the pattern for the derived refractive index plots for the

vitrinites at the anthracitic level became confused for

the maximum values but showed a distinct fall for the

minimum values.

The patterns of refractive index and absorption

index variation for carbonised vitrinites showed close

parallels with the variations of the X-ray parameters,

Lc, La, and d in carbonised coals referred to earlier

(Blayden et al., 1944). Other investigations under-

taken in the OGU on carbonised bitumens of different

types (Khavari-Khorasani and Murchison, 1978,

1979) clearly displayed the same close linkage

between the X-ray and optical parameters (Fig. 9)

(Khavari-Khorasani et al., 1978, 1979). With increas-

ing temperature, the pattern of variation of the Lc and

the refractive index curves, and the opposed trend of

the d spacing curve, reflect the combined influence of

three factors: increase in the height of the layer stacks

of dcrystallites,T improvement in the ordering and

packing of the aromatic layer planes within the

dcrystallites,T and reduction of the intralamellar dis-

tortion within the dcrystallites.T Reversal of the curve

trends in the 600–700 8C region suggests a change in

one or more of the factors involved in the progressive

development towards graphite, although the properties

of this mineral (Kwiecinska et al., 1977) were never

attained in any of these experiments. The La curves

reflect a progressive increase of the average layer

diameter of the aromatic layer planes with rising

temperature. The similar patterns of the absorption

coefficient (or absorption index) and La curves, which

both rise with increasing temperature up to about

1000 8C, suggest that absorption parameters and La

are influenced by the same structural factors.

4.4. The effects of igneous activity on sedimentary

organic matter in the northeast of England and the

Midland Valley of Scotland

4.4.1. Northeast England

The northeast of England would not immediately

be thought of as a spectacular igneous province. Yet

all forms of igneous activity are displayed, not

continuously stratigraphically, but still ranging from

the Devonian to mid-Tertiary. Exposed at surface in

the northern part of the Northumberland Trough are

Devonian lavas and small patches of weathered

Cheviot granite; the immediate post-Westphalian

Fig. 9. Variation of X-ray and optical parameters of the bitumen, gilsonite, carbonised up to a temperature of 1500 8C: (a) refractive index (nV),mean stack height (Lc) and average interlayer spacing (d) and (b) absorption coefficient (kV) and aromatic layer diameter (La) (reprinted from

the Journal of Microscopy, Khavari-Khorasani et al., 1978, with permission).


Great Whin Sill, underlying an area of at least 6000

km2 with its associated southwest- to northeast-

trending dykes, are found both on the Alston Block

and in the Northumberland Trough; and dykes of the

Tertiary igneous province, exemplified by the Cleve-

land dyke, which extends for 400 km from the west

coast of Scotland, run with a northwest to southeast

trend throughout the region. Unexposed and under-

lying the Alston Block, again of Devonian age, but

reactivated at times during the Carboniferous, is the

Weardale granite, which, aided by the Great Whin

Sill, had a marked influence on both the level and

extent of thermal alteration to coals and sedimentary

organic matter in the south of the region.

Organic petrologists, not only in Newcastle but

worldwide, have consistently shown interest in the

effects of igneous activity on coal seams, and more

recently also on its effects on dispersed sedimentary

organic matter. Even before Hutton, Lindley, and

Witham had written papers on the plant composition

of coals, Buddle (1831) and Foster (1831) had

published observations in local transactions on the

effects of igneous activity on coals in the Newcastle

area, as did Witham (1838) later, but none with

petrological input. Marshall (1936) seems to have been

the sole contributor to this area of coal petrology in

Newcastle in the first half of the 20th century, when he

described the effects of dyke intrusions on coal seams.

The microscopical aspects of the study were confined

to observations with air objectives on polished surfa-

ces. It is clear from a later paper on natural coke

(Marshall, 1945), published after he had left Newcastle,

that he was dissatisfied with reflected light examina-

tion, as it then was available to him in the UK, and he

reverted to studying thin sections of his natural cokes

by transmitted light—not a task leading to immense

fulfillment. Although he managed to prepare sections

as thin as 0.1 Am, the high optical absorption of the

more heavily affected parts of the coked coals yielded

little elucidation of their structure in transmitted light.

In complete contrast, the advent of effective

reflected light microscopical systems allowed Jones

and Creaney (1977) to give an excellent detailed

description of the behaviour of the optical properties

of macerals in coal seams as a dyke (or sill) was

approached. They commented particularly on the

polarisation direction in the vitrinite, which became

more random close to the dyke, with the vitrinite

becoming optically biaxial. Khavari-Khorasani et al.

(1990) found, after examining a number of instances

of dykes penetrating coal seams, that the decrease of

anisotropy did not explain all cases. Reflectance as

Fig. 10. Variation of maximum oil reflectance at 546 nm of vitrinites

with depth in the Whitley Bay Borehole, Northumberland, UK

illustrating the effect of sills and dykes on the properties of the

organic matter in a mature and compacted sedimentary sequence

(reprinted from the Journal of Microscopy, Jones and Creaney

1977, with permission).


well as bireflectance fell close to the dyke or sill

contacts and X-ray diffraction data indicated that the

vitrinites had been transformed to a carbonaceous

material with a turbostratic or paracrystalline struc-

ture. While the optical reversals may be due, in part,

to differing orientations of highly anisotropic frag-

ments, a combination of general molecular disorder-

ing and consequential variable surface quality of

prepared surfaces of semigraphitic-like materials is

also likely to be an important influence.

A number of critical boreholes were sunk in the

northeast region in the earlier part of this period and

they were most helpful to the expanding research

group: Harton (British Petroleum), Whitley Bay (Con-

oco, Amoco, and Safari), Weardale (Natural Environ-

ment Research Council), and Throckley (Institute of

Geological Sciences). Study of samples from these

boreholes was crucial to developing an appreciation of

how organic matter responded to variable but relatively

fast heating in the crust and to determining maturity

distributions in affected areas. Thus, Ridd et al. (1970),

in their work on the Harton borehole, showed that coal

rank in the Namurian had reached anthracitic level and

that, higher in the succession, Lower Westphalian

coals, on the basis of petrographic structures caused

through carbonisation by heat from theWhin Sill, must

have been of coking rank prior to sill injection around

ca. 295 Ma (Fitch and Miller, 1967). The same

relationships were displayed in samples from the

Whitley Bay borehole (Jones and Creaney, 1977), the

microscopic granular mosaic illustrating that again the

coals above the Whin Sill must have been of coking

rank before the sill was intruded and also that coals

below the sill were higher than coking rank (Fig. 10).

Although the Throckley borehole was terminated just

below the Whin Sill, data from samples from this

borehole pointed to the same conclusions (Scott and

Murchison, unpublished results).

The mapping and petrographic work of Creaney

(1980) demonstrated how the imposition of the

heating effects of the Whin Sill upon the high-rank

coals and high-maturity sedimentary organic matter

above the reactivated Weardale granite modified coal

rank distribution directly above on the Alston Block.

Heat due to the reactivation of the granite was also the

cause of the contrasting higher-rank levels in the

Durham coalfield to the east of the intrusion compared

with the much lower ranks in the contiguous North-

,

,

umberland coalfield lying to the north in the dTrough.TCreaney et al. (1985) also published a brief account of

onshore vitrinite reflectance variations in the north of

England, showing comparisons of reflectance patterns

within the dtroughsT and dblocksT of the region,

particularly in those areas where reflectance levels

were raised above the dblocksT during the Carbon-

iferous due to reactivation of the underlying granites.

4.4.2. Midland Valley of Scotland

Because of interest from the oil industry, attention

was also focussed at this time on the geothermal history

of the Midland Valley of Scotland during the Carbon-

iferous and early Permian. Coals are found throughout

all stratigraphic groups of the Carboniferous, with oil

shales abundant but stratigraphically more restricted

and confined to the Carboniferous rocks of the eastern

Midland Valley. Igneous activity was widespread, but

the investigations mainly concentrated on coals and

sedimentary organic matter, which were affected by

Fig. 11. Variation of maximum oil reflectance at 546 nm of vitrinites

with depth in the Boreland Borehole, Central Fife, UK, illustrating

the effect of sill injection on the properties of organic matter in a

relatively uncompacted, water-laden sedimentary sequence (cf. Fig

10) (reprinted from Raymond and Murchison, 1988b, with

permission from Elsevier).


two intrusive episodes when large-scale sill complexes

were injected. The first was a phase of different types of

alkali–doleritic intrusions associated with phreatic

volcanic activity in early to mid-Carboniferous times;

then some 20 million years later, a post-Westphalian

phase of tholeiitic and quartz–doleritic intrusions. This

second phase was associated with the injection of a

major belt of tholeiitic dykes, some 200 km wide,

across Scotland and northern England, suggesting that

this second phase of minor intrusions belonged to a

single tectono-magmatic event.

Much of the organic petrographic work relating to

the Midland Valley Carboniferous can be found in a

series of papers (Raymond and Murchison, 1988a,b,

1989, 1991a,b,c, 1992; Murchison and Raymond,

1989; Raymond et al., 1989; Murchison et al., 1991),

based mainly on samples from two sources: first, the

British Geological Survey core store at Murchison

House in Edinburgh and, second, inland and coastal

sections throughout the region. A number of impor-

tant outcomes from the work are embodied in the

following observations:

(i) Extensive igneous activity controlled much of

the level and distribution of organic maturation

within the Midland Valley. Although the pat-

terns of organic maturation are complicated, it

is possible to produce restricted rank maps for

some stratigraphic levels. Vitrinite reflectances

in the regional sense are low (below

%Roil=1.00) (Jones and Murchison, 1974),

but there is a gradual regional increase in

organic maturation from east to west, corre-

sponding with an increasing thickness of

volcanic pile in the central and westerly parts

of the Midland Valley graben, suggesting that

there may have been a greater bheat sinkQ in the

west in Carboniferous times (Murchison and

Raymond, 1989).

(ii) Widespread phreatomagmatic and Surtseyan-

type volcanic activity incorporated large

amounts of organic matter into pyroclastic

rocks. Rarely are vitrinite reflectance values of

the incorporated organic matter raised much

above the regional vitrinite reflectance levels,

suggesting incorporation of the organic matter

into ash streams in which water was an

important cooling and protective component

(Raymond and Murchison, 1988a, 1991b). The

close relationship of organic matter of all kinds

with volcanic and intrusive igneous activity has

.


conspicuously raised the level of parent poly-

cyclic aromatic hydrocarbons in the aromatic

fraction of organic extracts. These hydrocarbons

originate through combustion and/or pyrolysis

of organic matter by the high temperatures

caused by igneous activity. They may be

autochthonous, due to in situ combustion or

pyrolysis of organic matter, or derived indirectly

through absorption of the components from

sediments or even from air and water (Murch-

ison and Raymond, 1989). Large quantities of

unsubstituted polyaromatic hydrocarbons were

found in wood of immature rank (%Roil=0.39)

from Orrock Quarry in the Midland Valley,

despite the wood being well preserved and still

showing evidence of microbial degradation

(Raymond et al., 1989). Good preservation of

wood exposed to the heat of igneous activity is

not unusual, as shown by a charred sample

(%Roil=0.54) from Tertiary conglomeratic tuffs

on the Isle of Rhum, northwest Scotland (Allan

et al., 1975).

(iii) Post-Westphalian tholeiitic sills have produced

extensive reflectance aureoles above and below

the intrusions, similar in scale to those formed

in the organic matter of sediments and coals

affected by the consanguineous Whin Sill of

northern England (Fig. 10). No such pro-

nounced aureoles were produced by the Namur-

Fig. 12. Plots of the logarithms of thermal aureole widths, based on vitrinit

alkaline-dolerite sills, quartz-dolerite sills, and tholeiitic dykes in the Mid

sills were injected into uncompacted, water-laden sediments (reprinted

Geological Society of London).

ian to early Westphalian alkaline sills (Fig. 11),

despite these magmas being injected at similar

temperatures and in comparable volumes to the

tholeiitic magmas. The contrast between the

aureole dimensions is controlled by several

factors: the degree of consolidation of the

sediments, their pore volume of water when

invaded by the magma, the time period between

deposition of the invaded sediments and

emplacement of the intrusion, and the degree

of organic maturation at the time of the injection

(Raymond and Murchison, 1988b; Murchison

and Raymond, 1989). Mechanisms for the

emplacement of tholeiitic and alkaline–dolerite

sills have been suggested by Francis (1982) and

Walker and Francis (1987).

(iv) A correlation exists between the logarithms of

the thicknesses of sills and the widths of the

thermal aureoles of the quartz dolerites (Ray-

mond and Murchison, 1991c). Equivalent data

e reflect

land Va

from R

for the alkaline dolerites lie more than two

standard errors from the regression line for the

quartz–dolerite plots (Fig. 12). The width of

thermal aureoles suggests the way in which

potential source rocks in a low-maturity

sequence may have responded in generating

hydrocarbons and, depending on the scale of the

aureoles, the volumes of hydrocarbons that

could have been produced.

ances at 546 nm, against the logarithms of the thicknesses of

lley of Scotland and Northern England: the alkaline-dolerite

aymond and Murchison, 1991c, with permission from the


Establishing correct property relationships of

organic matter in igneous-affected sequences, which

are relatively undisturbed tectonically, is not too

difficult a challenge. In more tectonically disturbed

areas (e.g., in the Carboniferous of southwest Eng-

land, where Variscan burial, folding, and thrusting,

together with granite emplacement, have occurred),

evaluation of the maturity progression is more

difficult (Cornford et al., 1987).

Fig. 13. Relationship of maximum oil reflectances at 546 nm of

vitrinites against volatile-matter yields (dmmf) of coals of the

Maudlin (H) seam in the Northumberland and Durham coalfields

UK (reprinted from Pearson and Murchison, 1999, with permission

from Elsevier, and from unpublished data).

5. The years 1989–2003

The national Earth Science Review of 1989 was a

dramatic (and traumatic) time for the Department of

Geology at Newcastle and the beginning of a major

transformation of the OGU, although there were

complementary blessings. Undergraduate courses and

many staff were transferred elsewhere, notably to the

nearby University of Durham. A separate, free-stand-

ing, postgraduate institute, bFossil Fuels and Environ-

mental Geochemistry (FFEGI)Q, was formed in place

of the OGU. After 1989, the institute expanded and

offered two taught Master of Science and Diploma

programs (Environmental Biogeochemistry and Petro-

leum Geochemistry), which, in part, fed trained

students into facilities and training for full-time and

part-time research over a wide range of topics:

principally microbial geochemistry, ancient biomole-

cules, palaeoclimates, petroleum geochemistry, basin

modelling, and organic facies. Formal organic petro-

logical research and teaching, involving reflected light

methodology, diminished greatly. Organic petrology

was underpinned, first, by transmitted light micro-

scopy aimed at understanding factors controlling the

formation and composition of petroleum source rocks

in different environments and, second, by gaining an

understanding of the maturation history of the offshore

coalfields of northeast England.

Automated kerogen typing by image analysis

(Tyson, 1990) lay at the core of the new studies in

the book, Sedimentary Organic Matter: Organic

Facies and Palynofacies (Tyson, 1995). Palynofacies

was a new interest for the Newcastle group (Tyson,

1993) and much of the work of Tyson and his

collaborators involved the study of organic facies

from different parts of the stratigraphic column. Some

of this activity encompassed earlier interests of the

OGU (Frank and Tyson, 1995; Follows and Tyson,

1998). More recent investigations were concerned

with sequences abroad, for example, in the Upper

Cretaceous of the Pyrenees (Tyson and Follows,

2000) and the Kimmeridgian of the Boulonnais area

in Northern France (Tribovillard et al., 2001).

Continuing reflected light studies within the

changed research group related principally to the

offshore coalfields of Northumberland and Durham.

More recent results confirmed and extended data

published some years ago. For example, Pearson and

Murchison (1999), examining the relationship

between reflectance and volatile matter yield of coals

from the Maudlin Seam offshore (Fig. 13), showed

that the correlations between the two properties were

different for the two coalfields, confirming the

suggestions of Jones et al. (1984). The differences

are almost certainly due to contrasts in the thermal

histories of the sedimentary organic matter associated

with the Alston Block, on one hand, and with the

Northumberland Trough, on the other hand (see

Creaney, 1980), particularly to rate of heating. Data

arising from quite different types of investigations

support this view. For example, in studying the effect

of igneous activity on molecular maturation indices,

Raymond and Murchison (1992) showed that sam-

ples, which had attained a given rank through rapid

heating, may appear to be more immature, on the

basis of their molecular signatures, than samples that

,

Fig. 14. Variation of the methylphenanthrene index against level of

maturity (maximum oil reflectance of vitrinite at 546 nm) for type I

and type III organic matter exposed to different heating rates

(reprinted from Raymond and Murchison, 1992, with permission

from Elsevier).


have attained the same rank through a much slower

rate of heating (Fig. 14). Carbonisation experiments

involving variation of heating rate (Goodarzi and

Murchison, 1978) are similarly supportive.

The depression of vitrinite reflectances of coals

overlain by sandstones in borehole sequences of the

offshore Durham coalfield was reported by Jones et al.

(1972). That depression of reflectance in the coalfield

was firmly confirmed by Pearson and Murchison

(1990) using samples taken from below a colliery

Fig. 15. Contrast between oil reflectances at 546 nm of vitrinites in coals fr

UK), taken from beneath a shale and a contiguous dwashoutT sandstone (r

Elsevier).

washout sandstone and a contiguous shale overlying

the same coal. Not only were the reflectances of

vitrinites below the sandstone lower than those

beneath the shale, as in the borehole sequences, but

the volatile matter yields of coals below the sandstone

were also higher than for coals below the shale (Fig.

15). On the basis of earlier independent work,

Damberger (1965), in discussion of the paper by

Jones et al. (1972), stressed that it was unlikely that

differential thermal conductivity effects could be

responsible for the reflectance differences, although

no alternative persuasive explanation for the differ-

ences could be put forward at the time. Later work

(Correa da Silva and Wolff, 1980; Fermont, 1988;

Mastalerz, 1991) strongly suggested that the reflec-

tance differences probably originated in contrasting

processes operating early in the biochemical stage

during deposition of the sediments.

More certain are the causes for the now well-

established suppressions of vitrinite reflectances in the

presence of high liptinite contents and/or marine

influences at the time of deposition, which have

now been recorded in offshore Durham sequences by

Murchison and Pearson (2000). Raymond and Murch-

ison (1991a) established in the Midland Valley of

Scotland that normal reflectance trends differed

markedly from trends based on vitrinite reflectances

from samples in the same borehole containing

om the Ryhope Five Quarter seam (Vane Tempest Colliery, Durham,

eprinted from Pearson and Murchison, 1990, with permission from


amounts of liptinite in excess of 20% (Fig. 16). The

cause of the difference in the Midland Valley is most

probably due to the absorption by the vitrinites of

released aliphatic substances from the liptinites during

coalification (see also Khavari-Khorasani and Murch-

ison, 1988): in Durham, the cause is more likely to be

marine influences.

Fig. 16. Variation of the maximum oil reflectances at 546 nm of

vitrinites with depth in the Musselburgh No. 1 Borehole, Lothians,

UK, illustrating the difference between coalification tracks devel-

oped using vitrinites from samples with greater or less than 20%

exinite macerals (reprinted from Raymond and Murchison, 1991a,

with permission from Elsevier).

6. Summary and conclusions

The contribution of bNewcastleQ to coal petrol-

ogy, then organic petrology, over approximately 175

years has been substantial. Perhaps the greatest step

forward in the saga was the first by William

Hutton: bthe solution of the problem of demonstrat-

ing the vegetable structure in coal itselfQ (Murchi-

son, 1834). This is not to minimise in any way the

contributions of Hickling and Hickling and Marshall,

almost 100 years later, in this same area of plant

structures in coals. But the observations of Hutton,

Lindley, and Witham on the nature of coal were

fundamental and for the time remarkable, bearing in

mind the facilities that were available to them.

Although first suggested by Hutton, Hickling’s

recognition that the differing chemical compositions

of coals were as heavily controlled by their mix of

vegetation and the early degradation of that vegetation

during biochemical history, as they were by rank

level, was most important. Serious recognition to the

claim was hardly granted by many other coal

scientists at the time; indeed, it was many years

before due acknowledgement to this significant

influence on the chemical composition of coals was

awarded. The steel industry, with its need to improve

coke quality worldwide after the Second World War,

was a major factor in ensuring it was.

Raistrick’s work on the correlation of coal seams,

using their microspore populations, was again a

major advance that laid the foundation for the now

separate and important field of palynology. And 80

years after what was one of the major commercial

legal trials of the 19th century, Blackburn and

Temperly’s study of Botryococcus resolved the

long-standing problem of the origin of the algal

coals.

In the years after the end of the Second World

War, research in coal petrology, then more widely in

organic petrology, changed radically at Newcastle.

The OGU was formed with its two principal

components of organic petrology and organic geo-

chemistry. There was the switch to the more widely

applicable and useful reflected light methodologies

instead of transmitted light examinations; large

research groups, such as the OGU, became man-

datory, particularly if cooperation with industry was

envisaged; and coal research in the UK, partly


because of the structure of the industry, became a

diminishing prospect for active research groups in

the organic petrological field. But the flourishing

and expanding oil industry became an interested and

supportive agency of such groups and has remained

so ever since.

Although relationships between maceral proper-

ties, as well as the separation of the macerals and

assessment their properties, were a prime interest of

the OGU initially, a dominant root of organic

petrological research was the effect of raised

temperature on the organic constituents of rocks.

The results obtained were related as much to the

immediate needs of the carbonisation and petroleum

industries as they were to longer-term fundamental

research interests: for much of the time, these

interests were common. Because of this work and

due to the efforts of others elsewhere, the influence

of wide variations in temperature on different

organic entities, variably treated and from different

environments, is now better understood, as is what

happens to organic matter in geological successions

under a variety of conditions when magma injection

takes place. Murchison et al. (1985) gave an

assessment of the relevance of the optical properties

of crustal organic matter in relation to thermal and

structural regimes.

Beyond the national Earth Science Review of

1989, the position of organic petrology at Newcastle

again shifted radically when the new institute

(FFEGI) was formed. Transmitted light studies of

organic facies of marine and lacustrine potentially

oil-bearing rocks developed, although they were

not a large component of the institute’s research.

Work in reflected light was now principally

confined to understanding the distribution of rank

and its causes in the offshore coalfields of North-

umberland and Durham. Within these studies, a

pattern developed, perhaps not unexpectedly, which

suggests an extension of the onshore rank relation-

ships, that are related to the contrasting heating

regimes of the Alston Block and the Northumber-

land Trough.

The scale of organic petrology at Newcastle has

now diminished. Its future is more speculative, not

because it has become an irrelevancy, but because of

both external and internal factors. There is no coal

industry and the much-reduced needs of the steel

industry in the carbonization field are probably well

served. Those in the new School of Civil Engineering

and Geosciences need to continue to track relevant

research issues and to operate on an international

scale, not only in collaboration with the petroleum

industry, but also increasingly with environmentally

based organisations.

Acknowledgements

This paper would obviously not have been

written without the energy and efforts of colleagues

who have contributed to the research programs in

coal, then organic petrology, at Newcastle over

many years. The programs would not have pre-

vailed without the support of the university and

numerous organisations, both government and

industrial, but particularly the petroleum industry.

All are sincerely thanked. Christine Jeans has given

invaluable advice about the text figures.

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Documents

Organic petrology in the 19th, 20th, and 21st centuries: The Newcastle contribution