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Part 2. Lyell and the development of geological science

One could be forgiven for thinking that basin and dynamics was a field of study developed in the later part of the twentieth century. The rapid rise in sedimentology and basin analysis would support this view. In attempting to understand, and give credit for, the origin of a particular discipline, there is often a need to identify individuals who may be regarded as the founder. Clearly with sedimentology such a man was Sorby. In his contribution, Mike Leeder argues that a case can be made that it was Lyell rather than Sorby who was the true originator of sedimentology and basin analysis. Leeder critically analyses Lyell's sedimentological descriptions and field observation as published in the Principles. Leeder demonstrates that Lyell grasped many concepts both of processes and products, indeed he recognized a number of sophisticated sedimentological concepts. Leeder further documents Lyell's willingness to abandon firmly held views. It is also clear that Lyell was not anticatastrophist as is often claimed. From Leeder's analysis it is firmly established that Lyell was engaged in and indeed contributed to establishing as a truly scientific discipline. Of major interest to Lyell was the concept of geological time and its divisions. Lyell's studies on Tertiary molluscs and the establishment of geological periods based upon their percentage similarity to modern forms is well known. William Berggren discusses the development of Cenozoic stratigraphy including Lyell's terms Eocene, Miocene, Pliocene and Pleistocene and suggests changes to current nomenclature and concepts. The establishment of time as a major element in geological ideas and the recognition of changing faunas and floras through time caused many difficulties to in the nineteenth century. In his early work, as Tony Hallam points out, Lyell argued against organic progression. However, as data accumulated, Lyell eventually began to accept some kind of organic progression in the stratigraphic record whilst still believing in the imperfection of the fossil record. Hallam argues that it is not fair to criticize Lyell for his late and lukewarm conversion to evolution. Joe Burchfield takes the concept of time a step further and gives a considered account of how, through the course of the nineteenth century, Lyell and his contemporaries developed ideas from a general impression of the vastness of geological time to the clear recognition of a geological history of the Earth as a succession of events in the stratigraphic record and attempts to determine a chronology for the age of the Earth. If the general concensus at the end of the century gave the Earth an age of c. 100 Ma, to be disproved within a decade, no matter, the concept of geological time had been established and with it the essential scientific basis to quantify the rates of geological processes. Rapid climatic change and Quaternary glaciation provided a major challenge to Lyell. Patrick Boylan in his paper discusses Lyell's work in relation to the Glacial Theory of Louis Agassiz. Boylan documents the intensive field research of Lyell centred on his Scottish estate at Kinnordy. Lyell at first supported the Glacial Theory but hostility by a number in the Geological Society persuaded Lyell to revert to his earlier views of the importance of floating icebergs. However, by the end of his life he had begun to accept some highland glaciations but still continued to attribute deposits of the 'Glacial Period' to submergence. Whilst Lyell continued to have problems with the Glacial Theory, he was still particularly interested in climate change. In his paper, James Fleming examines Lyell's position on climatic change in geological and historical times, and explores the mutual influence of Lyell with James Croll who was a proponent of an astronomical theory of Ice ages. Clearly the period of 's active geological life was one when numerous important astronomical discoveries were being made and many theories being advanced about climate change. Fleming argues that Lyell was slow in modifying his views on climate change but only because he tempered his judgements with solid evidence gathered from the record of the rocks- a lesson we might all learn! It is clear from many of the contributions in this volume that labelling Lyell simply as a uniformitarianist who did not entertain catastrophes was not correct. Baker argues that working scientists are prone to misconceptions as to the relationship of philosophy to science. The 'new ' that Baker proposes is rooted in firm geological observation. Finally, in this section, Lyell Professor John Mather relates the historical development of hydrogeology in Britain through the nineteenth century, a subject of passing interest to Charles Lyell which was advanced in his day by geologists who needed practical solutions to locating groundwater supplies to support the growing industrialization of the nation. Lyell recognized that rainwater percolated through the ground to issue forth as springs at the junction of permeable and impermeable strata, and was interested in this as an Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

96 PART 2 aspect of the Earth's surface processes. But it was really only in the latter half of the century that the science of hydrogeology was established and hydrogeological maps were published. Derek J. Blundell Andrew C. Scott Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

Lyell's Principles of Geology: foundations of sedimentology

M. R. LEEDER School of Earth Sciences, University of Leeds, Leeds LS2 9JT, West Yorkshire, UK

Abstract: This chapter examines the extensive arguments Lyell brought to bear on the interpretation of sedimentary rocks through the operation of 'present causes' in the first Edition of Principles of Geology (1830-1833). A case is made inter alia for Lyell, rather than Sorby, being the true originator of sedimentology and basin analysis, amongst much else of course. Lyell had a special interest in Earth surface processes, and the effects of tectonics and climate on them, because he saw that the evidence is firmly written in the sedimentary products of observable events. His own explanations for the sedimentary and geomorphic processes of erosion and deposition were acutely sensible: he analysed (in today's parlance) river avulsions, controls on delta morphology, oceanic brine pools, cross stratification, confluence bars, boundary layers, hydraulic geometry, debris flows, sediment budgets, alluvial basin architecture, and clinoforms. Much of Sorby's work in some of these areas must have been inspired by his reading of the Principles. Lyell was occasionally too much guided by theory, as in the famous sophistry of his 1830 analysis (in the first edition) of the sedimentary and geomorphological evidence for Holocene Fenno-Scandinavian uplift. His willingness in subsequent editions of Principles to abandon such firmly held views in the light of empirical and personally collected field evidence to the contrary presages his momentous decision to throw his weight behind Darwin's natural selection theories some 30 years later. Lyell was not so rigidly an anti-catastrophist and inductionist as is commonly made out. His writings make very clear his ability to state bold theories. For example, his discussions of climatic change and his concept of the 'great year' were outstandingly incisive, holistic and original. They include the role of land-sea interactions, ocean currents and precessional orbital cycles. He even considered the probablity that continents and oceans changed position, albeit by vertical movements. The motive for all this came from observations he and others had made on the distribution of Cenozoic molluscs and the need for some general global cooling to explain these. He included in his actualism all manner of extreme (but not 'catastrophic') events, for example earthquakes and volcanic eruptions. He was also willing to consider (but then rejected) the possibility of catastrophes, most obviously in his discussion in the seventh edition of Principles (1846) of the possible 'lake-burst' of Lake Superior into the headwaters of the Mississippi. One feels he would have welcomed probability theory and the development of magnitude/frequency analysis, and that he would have laughed at any modern description of himself as the 'father of '.

It is tempting to view Charles Lyell as a remote Kennedy, who, according to his biographer (Sutton geological figure of only historical interest, with 1980, p. 301), during his distinguished tenure as little relevance today. The great work of his early Chair at Leeds (1946-1967), used to read through years, the first edition of Principles of Geology Principles before the beginning of each new acad- (Lyell 1830-1833), can thus be seen as a museum emic year to give himself the necessary inspiration item in the pantheon of early geological literature, for teaching. Nowadays the wide availability of the along with 's and first edition of Principles of Geology, via the William Smith's Geological Map of England and facsimile University of Chicago reprint, enables us Wales. This view is wrong, because geology is a all to confirm the essential modernity of much of special science in that much depends upon the Lyell's geological logic. Principles is an eternal primacy of field observations. Lyell was an acute stream from which we can all drink and refresh observer of Earth surface features and processes ourselves periodically. That the stream is a deep and the use of these in the interpretation of rocks. one, more than 1400 pages in total, is somewhat We can all relate to geologists of any age through off-putting but the majority of Lyell's views on their field observations; this stress on the empirical sedimentary topics are to be found concentrated in basis of geology is Lyell's hallmark, although, as volume 1, published in 1830. we shall stress later, he was also a serious theorizer Nowhere is Lyell's own contribution to geology when the mood took him. To illustrate the argu- more apparent than in his discussions of sedi- ments for relevance, consider the case of W. Q. mentary and stratigraphic issues (his observations

LEEDER, M. R. 1998. Lyell's Principles of Geology: foundations of sedimentology. In: BLUNDELL,D. J. & 97 Sr A. C. (eds) Lyell: the Past is the Key to the Present. Geological Society, London, Special Publications, 143, 97-110. Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

98 M.R. LEEDER on volcanics owed much to his friend Scrope). One There can be little doubt that Lyell evolved his often wonders how Lyell developed his abilities to worldview largely through his experiences of field read the rocks and the landscape so well. We cannot work in the southern European and Mediterranean pretend that he invented the philosophy of actual- regions. In his terminology these are areas of strong ism, but he certainly relentlessly pursued it. Case reproductive and destructive forces, contrasting after case is presented, from personal observations mightily with the relatively staid and stable land- and from a very wide variety of literature refer- scapes of his native Britain. Here in southern ences (for a helpful analysis see Rudwick 1991) Europe he got most of his mollusc evidence for from explorers, encyclopaedias and classical Cenozoic history and climate change, his earth- authors concerning modern analogues useful in the quake and volcanic evidence for uplift and depres- interpretation of sedimentary rocks in the strati- sion and his observations on the rates of infill of graphic record. The example of his much-travelled lakes and seas by deltas. We now know that the grandfather, the early readings in the great library richness of this Mediterranean field laboratory at Bartley Lodge (see Clasby 1997) and his arises from the complexities of its plate interactions Mediterranean-orientated classical education must and tectonics and the complications induced by all have played their part in setting up such an Quaternary climatic changes. But at the same time exceptionally broad-based approach. Although the it is interesting to note that the primacy there of analysis of physical processes is never technical in earthquakes and magmatic flow in causing uplift the sense of the use of mathematics, the approach is and subsidence severely embarassed Lyell because very modern in commonly using physical intuition it led to his earlier inability to understand how such and guideline calculations of rates of change (see processes operated without the aid of earthquakes the sections on fluid flow and sediment budgeting and volcanoes. Hence his lofty dismissal (Lyell below) 1830-1833, vol. 1, pp. 227-232) of the published field evidence for the uplift of Fenno-Scandinavia. A world view: reproduction versus His subsequent visit there in 1834 overcame his theoretical opposition and he then accepted the destruction field evidence. Without a theory to explain uplift, It has been said (Rudwick 1991, p. xi) that Lyell's this volte-face showed Lyell's devotion to empir- contemporaries were not particularly interested in a icism and his intellectual courage in rejecting a Huttonian worldview involving cyclic changes. But formerly strongly held conclusion. It presaged his in the Principles they found exactly that, though more momentous decision to throw his weight more subtly expressed. Most importantly to field behind Darwin's natural selection theories some 30 geologists, for on the whole they are not philosoph- years later. ically inclined, they could also find a piecemeal Lyell returns to the mass balance aspects of empirical approach to day-to-day geological erosion and deposition in Chapter 17 of Principles investigations based on 'modern causes acting at Volume 1, where he questions the destination of their present intensities'. This non-theorizing sediment produced by coastal erosion. In line with aspect influenced (usually to their advantage, but his philosophy of reproduction/destruction he sometimes to their detriment) subsequent gener- deduces that it must all go to make up the tidal ations of British and American geologists. But sandbanks and coastal salt marshes that are so ignorance of the wider picture is a misreading of characteristic of areas around the southern North the global message of Principles. Nowhere is Sea. In a splendid re-emphasis of his 'present Lyell's intent more obvious than in Volume 1, causes' philosophy (vol. 1, p. 311), he exorts where he lays out his basic philosophical position: geologists to go out and look for such effects in the that the outer Earth, the only realm of geological geological record: interest, is subject to the opposing tendencies of Those geologists who are not averse to presume what he calls 'reproduction' (sediment deposition, that the course of Nature has been uniform from lava eruption, uplift due to earthquakes) and the earliest ages, and that causes now in action 'destruction' (erosion). He saw all Earth surface have produced the former changes of the earth's processes as aimed towards one or the other of surface, will consult the ancient strata for these ends, with the resulting balance being the instruction in regard to the reproductive effects state of the Earth as we see it now, or at any time in of tides and currents ... they will then search the the the past. Thus it was Lyell's philosophy that as ancient lacustrine and marine strata for we look back through the Earth's history we should manifestations of analogous effects in times past. look for a similar balance. The geological revolution of the past 30 years tells us emphatically Perhaps the most stirring passage concerning the that Lyell's basic geological intuition and logic balances and checks between subsidence, uplift, were correct. deposition and erosion available in the natural Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

FOUNDATIONS OF SEDIMENTOLOGY 99 world (note his reference to the Earth's surface as a when estimating the mechanical power expended 'system') comprises the last two sentences of by running water. Quoting as reference the article Principles Volume 1: on rivers in Encyclopaedia Brittanica, he carefully restates (pp. 172-173) the experimental fact that ...subterranean movements...the constant repair stream channels have three-dimensional zones of of the dry land.., are secured by the elevating and retardation (known, since Prandtl's work early this depressing power of earthquakes...This cause century, as boundary layers) due to retardation of ...is...a conservative principle in the highest flow by friction at their solid boundaries. He also degree, and, above all others, essential to the notes from the same source the steadily increasing stability of the system. velocities needed to entrain and transport, respec- tively, clay, silt, sand, gravel and pebbles. Later, in Sedimentation rates and budgeting a discussion on the transporting capacity of rivers (vol. 1, p. 247), he admits surprise at the tremen- In Chapter 13 of Volume 1', Lyell turns to the dous variation in suspended sediment concen- 'reproductive' effects of running water. In a series trations recorded by different workers in different of striking phrases (p. 220), he engages us with his rivers. He is particularly intrigued by the record of ideas of the mechanical transfer of energy and a 25 per cent of suspended sediment by volume useful definition of total sediment discharge: 'The recorded by Rennell from the Ganges at flood aggregate amount of matter accumulated in a given stage. Although this particular figure has not been time at the mouths of rivers ... affords clear data for confirmed, we now know that such concentrations estimating the energy of the excavating power of are commonly reached in the Yellow River, leading running water on the land...' Such approaches still to the phenomena of hyperconcentrated underflows underpin the estimation of past sediment yields into the China Seas (Wright et al. 1986) from river catchments. Lyell then proceeds to In a long letter written in September 1830 to his outline some of the problems associated with such friend Scrope (Lyell 1881, pp. 296-299), in which estimates, chiefly concerning the role of lakes in he ruminates (quite wrongly it turns out) on the trapping sediment upstream from deltas. He returns origin of subaqueous sand ripples, Lyell concludes to the theme of estimating sediment yields at the by proposing a fluid mechanics experiment (Fig. 1) end of Chapter 14 ('Quantity of sediment in river that they might do to further their understanding of water'), with a discussion of the likely annual ripple formation: sediment influx from the Yellow River, Ganges and other rivers. He draws on previous conceptual A large and deep trough, with gently slanting advances and researches by others, but it is clear sides, might enable us to experiment. Get a that his ultimate goal is to estimate the total global paddle-wheel which will turn with the hand, and sediment flux from the continental surface to the make a ripple ad libitum, and sand and mud of oceans (p. 246): different kinds to be deposited. Then we will Very few satisfactory experiments have as yet been made, to enable us to determine with any degree of accuracy, the mean quantity of earthy matter discharged annually into the sea by some b c one of the principal rivers of the earth'

Lyell computes estimates of the Ganges sediment L~ yield and compares it to the volume of recent Etna lava flows. Here he is encouraging geologists to . estimate total global fluxes for continental erosion and oceanic deposition. This is entirely in line with ,,, - = his global view of balance and change. We continue I II ~ ~'~ to stumble towards such goals today. !lllJ ' = HJlilliil| i, I

Fluid flow Fig. 1. Side (top) and plan (bottom) views of the hand- Lyell frequently reveals an appreciation of the basic operated paddle wheel flume used by Ludwig Prandtl around 1900 (see Acheson 1990, pp. 260-299) to physics of sediment transport by fluid flow which elucidate the nature of boundary layer separation. Lyell was greatly in advance of his time. In discussing the suggested to Scrope in 1830 that they might use a similar 'transporting power of water' (vol. 1, p. 172 et artifice to investigate ripple formation, perhaps the first seq.), he notes that one must always take into planned (but never instigated) loose boundary hydraulics account the immersed weight of mineral grains experiment in the history of sedimentology. Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

100 M.R. LEEDER

afterwards mix matter in chemical solution. After a due series of failures, blunders, wrong guesses etc, we will establish a firm theory. Lyell ends with a typically acute remark, another product of his voracious reading and his pre- dilection for lateral thinking: 'Have you read Dr. Young's experiments on the arrangement of sand upon boards vibrating by different notes of stringed insruments? The symmetrical forms obtained are wonderful.' Here he is hinting at the ability of sand Fig. 2. A copy of the woodcut version (vol. 1, p. 254 fig. piles to arrange themselves into well organized 6) of Lyell's field sketch of cross stratification taken at forms when stimulated by vibrations. Nowadays the confluence of the Rivers Rh6ne and Arve in 1829. we are more familiar with the arrangement of The field of view is 3.66 m by 1.52 m. This is the first self-similar forms and the intriguing properties of published illustration, description and correct sand grains subject to shear and vibrations interpretation of a major sedimentary structure. The (Umbanhowar et al. 1996). deposits shown are the 1828 spring flood deposits of the Arve, as subsequently dissected by the Rhfne, observed at low river stage by Lyell in January 1829. See Fig. 3 for a modem explanation. Sedimentary structures Lyell had a special interest in sedimentary struc- tures and endeavours at several points in Principles fluence bar, specifically fronto-lateral avalanche to give detailed explanations of their origins. He and bar-top gravel-train strata: was clearly determined that geologists should use such features to improve their interpretations of These layers must have accumulated one on the sedimentary rocks and ancient environments. other by lateral apposition, probably when one of Inductive reasoning, from small to large, from the rivers was very gradually increasing or present to past, epitomizes most of Lyell's geological philosophy. It is nevertheless clear that observations should be made in a deductive spirit, i.e. testing preformed hypotheses, as revealed in another extract from his long letter to Scrope of 2 September 1830: I have for a long time been making minute drawings of the lamination and stratification of beds, in formations of very different ages, first with a view to prove to demonstration that at every epoch the same identical causes were in operation. Close description is followed by incisive and general comparisons with recent processes like those first encountered at the end of Chapter 14 (section on 'Stratification of deposits in deltas'). 1 2 Here (p. 254), he points out that deposited strata may not always be near-horizontal but may be 'disposed diagonally at a considerable angle'. He suddenly presents a sketch (Fig. 2), taken at the confluence of the Rivers Arve and Rhone, of a stratified sequence he observed in the incised flood deposits of the former fiver in the latter. This is the first illustration and serious explanation of cross- bedding in geological literature. The sketch shows tangential thinning-downward foresets, truncated Fig. 3. The flow field and avalanche faces of bars above by upper-phase plane beds, which are in turn formed at river confluences (from Bridge 1993; after succeeded by pebbly sand lenses. His description Best (1986) and Best & Roy (1991)). Lyell's sketch in and the exact location of the deposit leave little Fig. l pertains to the flow field at about section l of the doubt that we are looking at the deposits of a con- lower example of an unequal channel confluence. Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

FOUNDATIONS OF SEDIMENTOLOGY 101

Fig. 4. Copies of the woodcut versions (vol. 3, pp. 174-175; figs 31-34) of Lyell's field sketches of cross- stratification from the Plio-Pleistocene Crag deposits of East Anglia. Figure 31 is about 6.1 m high; fig. 32 4.88 m high; fig. 33 is 1.83 m high; fig. 34 is 1.22 m high. Lyell's fig. 33 was the first published illustration of 'herring-bone' cross-stratification. Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

102 M.R. LEEDER

diminishing in velocity, so that the point of greatest retardation caused by their conflicting currents shifted slowly, allowing the sediment to be thrown down in successive layers on a sloping bank. A modern analysis of confluence bar formation (after Best 1986, Best & Roy 1991) is seen in Fig. 3. During the past 170 years, the study of cross- stratification has revealed more about the nature of ancient environments than has any other sedi- mentary structure. Cross-stratification has revealed evidence for, among other things, palaeoflow vectors, depth of flowing water, types of bedforms, nature of lateral accretion and the way up of folded beds. It is usually assumed that Sorby (claimed by some as the 'father of sedimentology') w~as the first to recognize the true origins of cross-stratification, but clearly this honour (and appellation?) should go to the young Lyell. Sorby (1908) was certainly the first to relate the succession of sedimentary struc- tures to the relative strength of a flow and the Fig. 5. Wind-blown "ballistic' ripples of the type recognized and described by Lyell from the Calais nature of cross lamination to the rate of deposition, coastal dunes. Photo by the late Ian Wilson (his but it was Lyell who first figured and correctly handprint) taken c. 1970 in the Algerian Erg Oriental interpreted a variety of types of cross stratification (Wilson 1972). The arrow indicates wind direction. (Fig. 4). The main account is in the section on the East Anglian Plio-Pleistocene Crags, in Principles Volume 3, entitled 'Forms of stratification' (pp. 173-177). There is a revealing, though sometimes we may imagine a submarine bank to be nothing rather confusing, account in the letter to Scrope more than one of the ridges of ripple on a larger already noted. There is also a longer account in the scale, which may increase...by successive surviving London lectures of 1832-1833 (Rudwick additions to the steep scarps. 1976), in which Lyell attributes the formation of This is a profound advance, with Lyell deducing thick deposits of rippled sandsones to 'the drifting that a heirarchy of bedforms exists-from the lowly of sand grains at the bottom', presumably over current ripple up to larger dunes and channel-sized ripple forms. Climbing ripple cross-laminations sand waves. were termed 'ripple-drift' well into the mid He notes that in the Crags (and also in analogous twentieth century, usually associated with Sorby's forms in sandstones of the Old Red Sandstone, 1908 remarks but ultimately derived from this Lower Palaeozoic and other ages) shelly calcareous usage by Lyell. It is interesting that Lyell's inter- sands have layers oblique or diagonal to the general pretation of cross-stratification came from detailed true dip direction of the strata. He had obviously observations of tiny wind-blown ballistic ripples measured the directions of dip of the steep foresets (Fig. 5) forming on the coastal sand dunes at Calais. over large areas because he notes (p. 175) that all His arguments are too long to repeat here but we along the Suffolk coast these were generally to the may note (Fig. 6) his recognition of the asymmetric south, with the current responsible therefore from form of both wind-blown and subaqeous ripples, the north. These observations confirm Lyell, not steep leeward faces, lee-side avalanching and Sorby (whose observations were made in the late gradual downcurrent ripple migration. His 1840s and 1850s), as the first geological recorder impressive ability to scale up and his recognition and interpreter of cross stratification and palaeo- that the fluid physics of air and water are currents. He further notes (see Fig. 3), that certain comparable (Bagnold's detailed physical contrasts successive cross sets were orientated in opposing and comparisons (Bagnold 1951) lay far in the directions. This was the first published description future) are impressive (vol. 3, p. 177): of a key structure, which more than a century later We think that we shall not strain analogy too far (Reineck 1963) became known as 'herring-bone' if we suppose the same laws to govern the cross-stratification (Fig. 7). Lyell then goes on (p. subaqueous and subaerial phenomena; and if so, 177) to make a masterly analysis of the probable Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

FOUNDATIONS OF SED1MENTOLOGY 103

No. aS..

No. 36. d

Fig. 6. Copies of the engraved versions (vol. 3, p. 176; figs 35-36) of Lyell's sketches of asymmetric (wind-blown) ripples (fig. 36) and the origin of successive avalanche deposits of cross-stratification (fig. 35).

tidal origins of such structures and prepares the Lyell's discussion of the Mississippi River uses ground for geologists to measure the structures in material published by early explorers and naviga- other parts of the geological record. Sorby began tors. He presents descriptions of channel meanders, this mission some 20 years later. point bars, raised levees, the famous log jam at the

Modern sedimentary environments

Rivers In his discussions on the alluvial valley of the River Po (Chapter 11 of Volume 1), Lyell clearly refers to the infill of flood-plain lakes and marshes, and documents a number of 'deserted fiver courses'. This introduces the concept of river channel switches, or 'avulsions' as we now know them. Perhaps the most definite statement comes in Volume 1 (pp. 432--433), accompanied by his naming of the depositional fiver system as an 'alluvial plain': When we read of the drying up and desertion of the channels of rivers, the accounts most frequently refer to their deflection into some other part of the same alluvial plain, perhaps several miles distant. Under certain circum- stances a change of level may undoubtedly force the water to flow over into some distinct hydro- graphical basin; but even then it will fall immediately into valleys already formed. Such events are now best known and docu- Fig. 7. Illustration of opposed large-scale sets of mented from areas like the Saskatchewan River 'herring-bone' cross-stratification of the kind recognized (Smith et al. 1989; Smith & Perez-Arlucea 1994; by Lyell (see Fig. 4). Lebberston Member of the Middle Fig. 8) and from the active rift of the Rio Grande in Jurassic Cloughton Formation, Cloughton Wyke, New Mexico (e.g. Gile et al. 1981). Yorkshire. Arrows indicate flow directions. Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

104 M.R. LEEDER

Fig. 8. Oblique aerial photograph looking NNW to show the famous avulsion node of the New Channel (NC) of the Saskatchewan River, Canada (Smith et al. 1989; Smith & P~rez-Arlucea 1994). The avulsion from the course of the Old Channel (OC) occurred in the early 1870s, during Lyell's lifetime. Photo courtesy of M. P6rez-Arlucea.

confluence with the Atchfalaya and the general 192-197) is marked by great attention to detail. tendency of the Red River tributary junctions to be Both the New Hampshire and Swiss examples cited the site of periodic major flooding and lake involve descriptions of floods that we would now formation (alternating deposits formed by flooding refer to as hyperconcentrated flows: 'with as large at tributary junctions are further discussed in an a quantitiy of earthy matter as the fluid could hold insightful manner in Volume 1, pp. 245-246). Such in suspension'. considerations are rarely found in modern discus- Lyell is again thoroughly modern in frequently sions of alluvial facies and environments. quoting flood speeds and sediment/water discharge Lyell's most original and penetrating comments on magnitudes. Most important, in the light of river behaviour come when he integrates know- subsequent mocking cartoons by De La Beche ledge of river channel shifting, lake formation and (Haile 1997; Fig. 9), are his comments on the the occurrence of earthquakes like that of the large difficulties that misfit streams provide for 'present 1812 New Madrid event in the Mississippi valley cause' philosophy (p. 196, with author's emphasis): (vol. 1, p. 191): It is evident, therefore, that when we are The frequent fluctuations in the direction of speculating on the excavating force which fiver-courses, and the activity exerted by running running water may have exerted in any particular water in various parts of the basin of the valley, the most important question is not the Mississippi, are partly, perhaps, to be ascribed to volume of the existing stream, nor the present the co-operation of subterranean movements, levels of the river channel, nor the size of the which alter from time to time the relative levels gravel, but the probability of a succession of of various parts of the surface. floods, at some period since the time when some of the land in question may have been first This is strikingly modern in highlighting tectonic elevated above the bosom of the sea. tilting as a factor in fiver channel migrations and avulsions (see Alexander & Leeder 1987). Lyell would surely have delighted in the The short discussion of major historic river development of probablity analysis of floods and floods and their sediment transporting power (pp. their magnitudes (Nash 1994). Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

FOUNDATIONS OF SEDIMENTOLOGY 105

Fig. 9. De la Beche's satirical cartoon (brought to light by Haile 1997) mocking the effects of present causes. The child is peeing into the huge valley and a caption has his nurse exclaiming, 'Bless the baby! What a walley he have a- made.!!!' The cartoon is entitled 'Cause and Effect'. Reproduced courtesy of Professor W. J. Kennedy, University Museum, Oxford.

A further neglected example of Lyell's propen- of Mediterranean waters to form the present Black sity for speculative deductive analysis is his direct Sea (Ross et al. 1970). contemplation of a truly catastrophic scenario painted in the seventh edition of Principles in 1846 Deltas (p. 152). He is considering the vexed question of 'deluges' and states: In Chapter 13 of Volume 1 Lyell divides deltas into three types according to the nature of their outfall: ...it would seem that the two principal sources of freshwater, inland sea (e.g. the Mediterranean) and extraordinary inundations are, first, the escape of oceanic. He clearly defines and separates the the waters of a large lake raised far above the sea; influences of tidal current and river influences on and secondly, the pouring down of a marine delta form and processes, and in Chapters 13 and 14 current into lands depressed below the mean discusses in detail the lake and marine deltas of the level of the ocean. Rh6ne, Po, Nile, Ganges and Mississippi. Lyell specifically mentions, as a possible His discussion of the impact of the River Rhrne example of the former, the escape of the waters of upon the shoreline of Lake Geneva draws upon Lake Superior into the headwaters of the depth soundings made by De la Beche and is Mississippi. He rejects the possibility of such an distinguished by a clear account of what we would event occurring suddenly and considers that, even now term delta progradation and the production of if it did, catastrophic effects downstream would not low-angle delta foreset clinoforms (vol. 1, p. 221): necessarily follow. This is a 'catastrophist' thought We may state, therefore, that the strata annually experiment (albeit an 'Aunt Sally') of considerable produced are about two miles in length: so that, daring and ingenuity that we must now see in the notwithstanding the great depth of the lake light of the twentieth-century discovery of the (about 160 fathoms), the new deposits are not 'lake-burst' of glacial Lake Missoula. Examples of inclined at a high angle; the dip of the beds, the marine flooding scenarios that were cited indeed, is so slight, that they would be termed, in include the possible inflow of Mediterranean or ordinary geological language, horizontal. Black Sea waters into the depressed Caspian-again an 'Aunt Sally' but made more interesting to the After noting the likely coarse/fine alternations historian of ideas by the discovery of the desiccated (i.e. 'varves' in modern parlance) to be expected in Miocene Mediterranean and its subsequent filling the foresets due to alternating yearly snowmelt and by the Atlantic (Hs0 et al. 1977), and by the glacial low-stage summer discharges, Lyell states: 'If then, isolation of Lake Euxine and the subsequent inflow we could obtain a section of the accumulation Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

106 M.R. LEEDER formed, in the last eight centuries, we should see a conditions pertaining to deposition of the Lower great series of strata, probably from six to nine Cretaceous Horsham Sands (see Allen 1975, pp. hundred feet thick, and nearly two miles in length, 413-415). He describes extensive thin bioturbated inclined at a very slight angle.' He then goes on to sandstones, the tops extensively rippled and the contrast these low angle clinoforms with the bases preserving desiccation cracks penetrating the increased dips expected from other smaller but interbedded clays. Noting the presence of fresh- steeper torrents entering the lake margins. He water shells and large reptiles in the sequence he here anticipates G. K. Gilbert's account (1885) of deduces that the desiccation took place between 'angle-of-repose' deltas in the Pleistocene lakes of tides. the Great Basin; deposits we now know as Gilbert As noted, Lyell's studies of the sedimentary deltas. structures in the East Anglian Crags were epoch Lyell's careful analysis of delta and shoreline making. Taking this together with faunal evidence, advance around Lake Geneva and his reliance on he proposed an insightful environmental analogue earthquakes as the sole means of crustal uplift led for the conditions of Crag deposition (vol. 3, p. to the famous sophistry of his weak attempt to 182): 'the formations which may now be in demolish Celsius' and subsequent workers' evid- progress in the sea between the British and Dutch ence for Fenno-Scandinavian uplift (vol. 1, pp. coasts, - a sea for the most part shallow, yet having 227-232). Lyell simply and dogmatically ends his here and there a depth of 50-60 fathoms, and where discussion by saying: 'No earthquakes, no uplift; strong tides and currents prevail'. all relative changes in shoreline position here are due to shoreline deposition'. Lyell's discussions of the marine deltas of the Po, Basin analysis and ancient sedimentary Rhrne, Ganges and Mississippi are perhaps his environments most sustained and successful analysis of 'present The penultimate section of Chapter 14 of Volume 1 causes' in the whole of Principles. His descriptions (pp. 249-251) contains an inspiring account of of freshwater, marine and hypersaline interactions 'some general laws of arrangement which must and their effects upon faunas at the mouth of the evidently hold good in almost all the lakes and seas Rh6ne anticipate by 150 years our concepts of now filling up'. We would now call this 'arrange- schizohaline (Folk's term of 1974) environments. ment' the stratigraphic architecture of an infilling He clearly separates estuaries from deltas and, for basin. It is worth quoting Lyell in full here to reveal the Ganges, notes in telling prose (vol. 1, pp. the depth of his thoughts on the matter and their 244-245) that the correspondence of fiver flood relevance for the interpreting ancient with strong gales and high spring tides generates rocks. Basically he is describing the gradual infill catastrophic (his word!) flooding and thus of any tectonic depression with transverse and axial sedimentation or erosion. Noting the low tides fiver and delta systems: affecting the Mississippi delta in the Gulf of Mexico, he remarks (p. 245) that 'the delta of the If a lake, for example, be encircled on two sides Mississippi has somewhat of an intermediate by lofty mountains, receiving from them many character between an oceanic and Mediterranean rivers and torrents of different sizes, and if it be delta.' bounded on the other sides, where the surplus He returns to discuss the effects of tidal currents waters issue, by a comparatively low country, it on North Sea estuaries and deltas, chiefly the is not difficult to define some of the leading geo- Rhine, in Chapter 16 (pp. 285-286), highlighting logical features which will characterize the the antagonistic forces of the tide and river: 'the lacustrine formation when this basin shall have one striving to shape out an estuary, the other to been gradually converted into dry land by influx form a delta'. Earlier comments on river channel of fluviatile sediment. The strata would be avulsions are reinforced by this statement, 'It is divisible into two principal groups; the older common, in all great deltas, that the principal comprising those deposits which originated on channels of discharge should shift from time to the side adjoining the mountains, where numer- time.' This presages the influential concept of delta ous deltas first began to form; and the newer lobe switching introduced by Gulf Coast workers group consisting of beds deposited in the more (e.g. Coleman & Gagliano 1964) in the 1960s. central parts of the basin, and towards the side farthest from the mountains. The following characters would form the principal marks of Estuarine shorelines and shelf seas distinction between the strata in each series. The In the surviving notes for the 1832-1833 London more ancient system would be composed, for the lectures (see Rudwick 1976), we hear Lyell most part, of coarser materials, containing many analysing his evidence for estuarine shoreline beds of pebbles and sand often of great thickness, Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

FOUNDATIONS OF SEDIMENTOLOGY 107

and sometimes dipping at a considerable angle. never advances ideas on world wide (eustatic) sea These, with associated beds of finer ingredients, level change. Lyell also thought correctly that the would, if traced round the borders of the basin, action of tides caused the mean sea level at any one be seen to vary greatly in colour and mineral time to vary. In a comment directly relevant to composition, and would also be very irregular in modern sequence stratigraphy he states, 'It is thickness. The beds, on the contrary, in the newer scarcely necessary to remark how much all points group, would consist of finer particles, and relating to the permanence of the mean level of the would be horizontal, or very slightly inclined. sea must affect our reasoning on the phenomena of Their colour and mineral composition would be estuary deposits.' He draws attention to the nature very homogeneous throughout large areas, and of currents formed by strong onshore winds and would differ from almost all the separate beds in correctly identifies the phenomena of leeshore the older series. superelevation. He deduces (p. 294) that, on ces- The following are the causes of the diversity sation of any storm, strong offshore currents would here alluded to between the two great members result which could transport sediment far offshore. of the lacustrine formation. When the rivers and Nowadays we call these a storm surge, super- torrents first reach the edge of the lake, the elevation causing a steady seaward surge (gradient detritus washed down by them from the current) during the storm, due to the balance of adjoining heights sinks at once into deep water, hydrostatic and dynamic forces. all the heavier pebbles and sand subsiding near On p. 296 of Principles Volume 1 there is a the shore. The finer mud is carried somewhat particularly insightful discussion based upon naval farther out, but not to the distance of many miles, surveys and Wollaston's analysis of the water for the greater part may be seen, where the balance and currents between the Mediterranean Rhone enters the Lake of Geneva, to fall down in and the Atlantic via the Straits of Gibraltar. This clouds to the bottom not far from the river's leads to the recognition of saline deep water mouth. Certain alluvial tracts are soon formed at currents and what was probably the first proposal the mouths of every torrent and river, and many for the origin of ocean floor brine pools. Examples of these, in the course of ages, become several of these have been discovered in the Mediterranean miles in length. Pebbles and sand are then in the last two years. Lyell clearly gives geologists transported farther from the mountains, but in a deep-brine model for the origin of ancient their passage they decrease in size by attrition, evaporites: and are in part converted into mud and sand. At the heavier fluid does not merely fall to the length some of the numerous deltas, which are all bottom, but flows on till it reaches the lowest part directed towards a common centre, approach of one of these submarine basins into which we near to each other- those of adjoining torrents must suppose the bottom of this inland sea to be become united, and are merged, in their turn, in divided. By a continuance of this process, the delta of the largest river, which advances additional supplies of brine are annually carried most rapidly into the lake, and renders all the to deep repositories, until the lower strata of minor streams, one after the other, its tributaries. water are fully saturated, and precipitation takes The various mineral ingredients of each are thus place ... on the grandest scale-continuous blended together into one homogeneous mixture, masses of rock salt ... like those in the mountains and the sediment is poured out from a common of Poland, Hungary, Transylvania and Spain. channel into the lake. Today's models for rift or foreland basin infill (see Busby & Ingersoll 1995) are essentially Climate and ocean currents similar, though with 150 years' worth of additional Lyell was passionately interested in climatic and accumulated jargon. oceanographic influences on the distribution and succession of faunas, floras and sediments. It is Sea level, ocean currents and deep brine noteworthy that he devotes the first three scientific chapters of Principles to these themes after lengthy, pools and polemical, introductory philosophical and Lyell was concerned about the possibility the historical material. These chapters mark him out world's oceans do not share a common absolute most emphatically as a holistic Earth scientist in the elevation of mean surface (vol. 1, p. 293 et seq.), a modern sense. After considering the geological possibility we now know as fact. He cites several evidence for climatic change in Chapter 6, he con- measurements suggesting that mean levels of structs possible scenarios that could account for it different seas and oceans did in fact differ, although on a global scale. He first points out the nature of we must stress (following Dott 1996) that Lyell continentality and proximity to oceans via a Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

108 M.R. LEEDER discussion of the Gulf Stream and its effects. He Lyell's science (e.g. Dott 1996 p. 126) and of sees the changing distribution of land and sea as the theories for climate change (Imbrie & Imbrie 1979) main immediate cause for climate change and he is have generally neglected that these proposals were ready to invoke uplift and submergence on massive made as early as the 1830s. Here is the relevant scales in order to effect the necessary changes in passage in Principles (vol. 1, p. 110): ocean current circulations. Here (vol. 1, p. 105) is It is, however, of importance to the geologist to his main point: bear in mind, that in consequence of the pre- But if, instead of vague conjectures as to what cession of the equinoxes the two hemispheres might have been the state of the planet at the era receive alternately, each for a period of upwards of its creation, we fix our thoughts steadily on the of 10 000 years, a greater share of solar light and connection at present between climate and the heat. This cause may sometimes tend to counter- distribution of land and sea; and if we then balance inequalities resulting from other circum- consider what influence former fluctuations in stances of a far more influential nature; but, on the physical geography of the earth must have the other hand, it must sometimes tend to had on superficial temperature, we may perhaps increase the extreme of deviation which certain approximate to a true theory. combinations of causes produce at distant epochs. By 1847 and the seventh edition these notions had hardened into maps showing the likely In later editions, from the third (1834) onwards, disposition of continental masses that might lead to Lyell also discussed the possible influence upon temperature extremes in the geological past. (see climate of eccentricity variations in the Earth's Fleming Fig. 1, in this volume). orbit around the Sun. It was the astronomer John Lyell's willingness to undertake bold and Herschel who originally suggested that eccentricity startling thought experiments in his quest for may have a role in climate change, albeit with little scientific explanation of geological evidence is best direct effect on the magnitude of incoming solar seen in this statement (vol. 1, p. 121): radiation, in a paper read to the Geological Society (but not published) in 1830. Herschel acknowl- That some part of the vast ocean which forms the edged (letters of February 1865 to James Croll; in Atlantic and Pacific, should at certain periods Irons 1896, pp. 121-122, 126-127) that Lyell was occupy entirely one or both of the polar regions, the first to suggest a role (albeit subordinate) for the and should extend, interspersed with islands, influence of orbital variations on ancient climates. only to the parallells of 40 ~ and even 30 ~ is an Such serious investigations by Lyell and Herschel event that may be supposed in the highest degree into orbital theories of climate change considerably probable, in the course of many great geological pre-date the efforts of the Frenchman Adhrmar in revolutions. 1842, the person wholly responsible according to I have emphasized the last phrase to draw atten- one influential account (Imbrie & Imbrie 1979, pp. tion to Lyell's use of the word 'revolution', clearly 80-83). I am not claiming here that Herschel and meant literally, in the context of cyclical change. Lyell pre-empted glacial theories but there can be More shocks are in store. On p. 110 of Volume 1, little doubt that the emergence of Croll's glacial Lyell draws attention, a little hesitantly, to the theory after Agassiz's epoch-making field obser- precession of the equinoxes and their role in a vations owed much to them as progenitors of the possible 20 ka climatic cycle. After noting the concept of climate change (Croll had carefully read existence of such long period cycles of climatic Lyell's Principles) (see also Fleming in this influence, he develops his concept of a 'great year', volume). a profound proposal somewhat ruined by the following fanciful remarks (much publicized and ridiculed by his opponents) on the reappearance of ichthyosaurs and other clearly extinct beasts during Lyelrs sedimentary legacy its course. Lyell's concept of a 'great year' is It seems to the author that there are four major analogous to, but clearly on a longer time scale trends in modern sedimentary geology: than, the astronomical cycle of the approximately 20 ka precessional orbital modulation (itself (1) an analytical one seeking explanations of discovered by the French physicist d'Alambert in processes in terms of fundamental physics and the eighteenth century). Lyell held its effects jointly chemistry; responsible (though as junior partner) for climate (2) an empirical one pursuing explanations of change, in conjunction with the changing distri- sedimentary rocks in terms of a descriptive butions of land and sea and the albedo effects of comparison with modern processes and land and sea, ice and snow. Historians of both products; Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

FOUNDATIONS OF SEDIMENTOLOGY | 09

This is not the place for more general comments on Lyell's legacy to geological posterity but it seems safe to conclude that his enthusiasm for field observations, his devotion to the pure sciences and, at the same time, for speculative deduction have had much to do with the healthy growth of what we might call (dangerously) hypothetico-empiricism in geology. Darwin, to take the most famous example, was certainly fired up by Principles because of this heady mixture of theory and observations; doubt- less countless others were too, including, no doubt, Sorby. Exactly what made Lyell himself think and act this way must await more systematic study, but we can imagine the active adolescent, alive with ideas and energy, rushing home with some natural specimen (dead rock or living thing) to Bartley Lodge, tipping off his boots and sliding along to his father's library in stocking feet to consult this or that reference among the many books in that marvellous place. The author believes that Lyell's heritage continues today, for, even in the depths of the economic depression from the mid-1980s to mid-1990s, British students still flocked into universities in their thousands to study our subject. This was in stark contrast, for example, to the USA, where economic factors prevailed and doubtless Lyell's original profession, that of lawyer, seemed Fig. 10. Henry Clifton Sorby (hand lens at the ready) as more lucrative to many. a young man in the 1840s. Sorby and Lyell are recorded as having met on some of the former's rare visits to I thank Derek Blundell and Andrew Scott for their London from Yorkshire. Original in the City of Sheffield invitation to contribute this paper as part of the Lyell Museum. bicentenary birthday celebrations. Thanks to them I have spent scores of happy hours poring over Principles and ruminating on the particular genius of the young Charles Lyell; a humbling but also inspiring experience. Thanks to my Leeds colleagues Jim Best and Jane Francis for (3) a regional and integrative one that relates reading and commenting on the manuscript and for their erosion and sedimentation to tectonic uplift and encouragement. I thank Philip England for some igneous processes in sedimentary basins; revealing discussions on Lyell and for correcting an error (4) a visionary global one that sees Earth surface in my interpretation of Lyell's concept of the 'great year'. processes uniting to provide a global budget of It is a particular pleasure to thank Perce Allen for the sediment and chemicals into the oceans, where tremendous job he did in improving the clarity and they are recycled and renewed by plate margin grammar of my text, and also Paul Clasby for finding processes. textural errors. I am also grateful to Andrew Scott for his editorial help, to W. J. Kennedy of the University Lyell's Principles can be seen as the fertile Museum, Oxford, for permission to reproduce Fig. 9 and beginning of all of these interrelated themes. It to Marta P~rez-Arlucea for providing Fig. 8. becomes clear that the young Sorby (Fig. 10) had stood upon the shoulders of a giant when we read References that he was able to recollect, in old-age (Kendall & Wroot 1924, p. 110), the 'discovery' he had made ACHESON, D. J. 1990. Elementar3' Fluid Dynamics. during a walk in about 1847: Oxford University Press, Oxford. ALEXANDER,J. A. & LEEDER, M. R. 1987. Active tectonic when walking from Woodbourne to Orgreave, I control of alluvial architecture. In: ETHERIDGE,F. G. was caught in a shower of rain, and whilst & FLORES, R. M. (eds) Recent Developments in sheltering in a quarry near Handsworth my Fluvial Sedimentology. Special Publication of the attention was attracted by what I afterwards Society of Economic Palaeontologists and Mineralogists, Tulsa, OK, 243-252. called 'current structures', namely structures ALLEN, P. 1975. Wealden of the Weald: a new model. produced in stratified rocks by the action of Proceedings of the Geologists' Association, 86, currents present during the time of deposition. 389--437. Downloaded from http://sp.lyellcollection.org/ by guest on September 27, 2021

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BAGNOLD, R. A. 1951. The movement of a cohesionless KENDALL, P. E • WROOT, H. E. 1924. Geology of granular bed by fluid flow over it. British Journal of Yorkshire. Privately printed, Vienna. Applied Physics, 2, 29-34. LYELL, C. 1830-1833. Principles of Geology. 3 vols. BEST, J. L. 1986. The morphology of river channel Murray, London. (Facsimile reprint, University of confluences. Progress in Physical Geography, 10, Chicago Press, Chicago, 1991) 157174. LYELL, K. (ed.) 1881. Life, Letters and Journals of Sir -- & RoY, A. G. 1991. Mixing-layer distortion at the Charles Lyell, Bart. Murray, London. confluence of channels of different depth. Nature, NASH, D. B. 1994. Effective sediment transporting 350, 411-413. discharge from magnitude-frequency analysis. BRIDGE, J. S. 1993. The interaction between channel Journal of Geology, 102, 79-95. geometry, water flow, sediment transport and REINECK, H.-E. 1963. SedimentgefiJge im Bereich der deposition in braided rivers. In: BEST, J. L. & stidlichen Nordsee. Abheilung senckenbergische BRISTOW, C. S. (eds) Braided Rivers. Geological naturforschung Gesselschaft, 505. Society, London, Special Publications, 75, 13-71. Ross, D. A., DEGENS, E. T. & MAClLVAINE,J. 1970. Black BUSBY, C. & INGERSOLL, R. V. (eds) 1995. Tectonics of Sea: recent sedimentary history. Science, 170, Sedimentary Basins. Blackwell, Boston. 163-165. CLASBY, P. S. 1997. Bartley Lodge and Sir Charles Lyell. RUDWlCK, M. J. S. 1976. Charles Lyell speaks in the The Hatcher Review, Winchester, 1-11. lecture theatre. Journal of the History of Science, 9, COLEMAN, J. M. & GAGLIANO, S. M. 1964. Cyclic 147-155. sedimentation in the Mississippi river delta plain. 1991. Introduction. In: LYELL, C. Principles of Transactions of the Gulf Coast Association of Geology. Facsimile reprint, 3 vols. University of Geological Societies, 14, 67-80. Chicago Press, Chicago. DoTr, R. H. 1996. Lyell in America- his lectures, field SMn-H, N. D. & I~REZ-ARLUCEA, M. 1994. Fine-grained work, and mutual influences, 1841-1853. Earth splay deposition in the avulsion belt of the Lower Sciences History, 15(2), 101-140. Saskatchewan River, Canada. Journal of FOLK, R. L. 1974. The natural history of crystalline Sedimentary Research, B64, 159-168. calcium carbonate: effect of magnesium content and ---, CROSS, T. A., DUFFICY, J. P. & CLOUGH, S. R. 1989. salinity. Journal of Sedimentary Petrology, 44, Anatomy of an avulsion. Sedimentology, 36, 40-53. 1-23. GILBERT, G. K. 1885. The topographic features of lake SORBY, H. C. 1908. On the application of quantitative shores. Annual Report of the United States methods to the study of the structure and history of Geological Survey, 5, 69-123. rocks. Quarterly Journal of the Geological Society GILE, L. H., HAWLEY, J. W. & GROSSMAN, R. B. 1981. of London, 64, 171-233. Soils and geomorphology in the Basin and Range SUTTON, J. 1980. William Quarrier Kennedy. area of southern New Mexico. Guidebook to the Biographical Memoirs of Fellows of the Royal Desert Project. New Mexico Bureau of Mines and Society, 26, 275-303. Mineral Resources Memoir, 39, Socorro. UMBANHOWER, P. B., MELO, F. & SWINNEY, H. L. 1996. HALLE, N. S. 1997. The 'piddling school' of geology. Localised excitations in a vertically vibrated Nature, 387, 650. granular layer. Nature, 382, 793-796. HsO, K. J. ET AL. 1977. History of the Mediterranean WILSON, I. G. 1972. Aeolian bedforms- their develop- salinity crisis. Nature, 267, 399-403. ment and origins. Sedimentology, 19, 173-210. IMBRIE, J. ~ IMBRIE, K. P. 1979. Ice Ages: Solving the WRIGHT, L. D. L-T AL. 1986. Hyperpycnal plumes and Mystery. Macmillan, NY. plume fronts over the Huanghe (Yellow River) delta IRONS, J. C. 1896. Dr. Croll's Life and Work. Stanford, front. Geo-Marine Letters, 6, 97-105. London.