Geological Sense Research Articles

‘The first true Silurian’ : an evaluation of the site of Murchison's discovery of the Silurian

In 1831 Sir Roderick Impey Murchison undertook an extensive geological fieldwork tour of England and Wales. He recounted retrospectively that one of the most momentous aspects of that tour was his encounter with greywacke rocks at a place called Cavansham Ferry in the valley of the River Wye in Wales. It was here that Murchison first decided that there was sufficient evidence to enable him to make a systematic study of the greywacke rocks which was to culminate in the publication of ‘The Silurian System’ in 1839, and he came to regard the site as ‘The first true Silurian’. Using original source material, maps and fieldwork, evidence is presented for the geographical location of the site, Murchison's movements and his geological thinking in the field. Although other locations became more important for stratigraphical purposes, it is argued that Murchison made several seminal discoveries in the Wye valley which led him to regard this site as the first place he encountered rocks that were to be later named as Silurian in a truly geological sense.

Chapter 7 Northeastern Spitsbergen

The land (area) considered here is bounded on the west by Wijdefjorden and on the east by Hinlopenstretet and Storfjorden. The southern boundary is somewhat indefinite. For descriptive convenience Carboniferous through Triassic stratigraphy is treated in Chapters 4 and 5 and Devonian strata to the northwest in Chapter 8. It makes geological sense for these chapter areas to overlap where they meet. Ny Friesland was the name for most of the area under consideration. However, after the accession of the Norwegian King Olav V in 1957 his name was given to what had previously been a somewhat indefinite territory, mostly ice covered (the Terre Glacee Russe of some older maps) to the south east of Ny Friesland. Olav V Land was defined to take in some of what had been referred to as Ny Friesland and early accounts should be read with this in mind (Miloslavskiy et al. 1993, map D8G). This chapter thus concerns Ny Friesland and north western Olav V Land and for descriptive economy Ny Friesland will be used for the area where most of the older rocks crop out. Much of the interior is covered by highland ice rather than an ice cap, meaning that the ice is not thick enough for the surface to be independent of the underlying relief. Indeed the ice cover is broken here and there by rocky cliffs of submerged valley glaciers. The three largest areas of continuous ice are Lomonosovfonna, Asgardfonna and Valhallfonna. The inland ice flows out along valley

Deformation across the western United States: A local estimate of Pacific‐North America transform deformation

We obtain a locally based estimate of Pacific‐North America relative motion and an uncertainty in this estimate by integrating deformation rate along three different paths leading west across southwestern North America from east of the Rio Grande Rift to near the continental escarpment. Data are primarily Quaternary geologic slip rate estimates, and resulting deformation determinations therefore are “instantaneous” in a geologic sense but “long term” with respect to earthquake cycles. We deduce a rate of motion of the Pacific plate relative to North America that is 48±2 mm/yr, a rate indistinguishable from that predicted by the global kinematic models RM2 and NUVEL‐1; however, we obtain an orientation that is 5–9° counterclockwise of these models. A more westerly motion of the Pacific plate, with respect to North America, is calculated from all three paths. The relatively westerly motion of the Pacific plate is accommodated by deformation in the North American continent that includes slip on relatively counterclockwise‐oriented strike‐slip faults (including the San Andreas fault), which is especially relevant in and south of the Transverse Ranges, and a margin‐normal component of net extension across the continent, which is especially relevant north of the Transverse Ranges. Deformation of the SW United States occurs in regionally coherent domains within which the style of deformation is approximately uniform. In the vicinity of the Transverse Ranges, two important shear systems splay from the San Andreas fault: the eastern California shear zone trending NNW from the eastern Transverse Ranges and the trans‐Peninsular faults trending SSE from the western and central Transverse Ranges. Within the Transverse Ranges the right‐lateral San Andreas fault steps left, seemingly requiring large amounts of convergence there. However, most of this convergence is avoided through a “funneling flow” of the crust toward the western Transverse Ranges and into the relatively narrow central California Coast Ranges and the northern motion of the Mojave. The former process involves an alternation of rotation direction from counterclockwise (in and south of the central Transverse Ranges) to clockwise (in the western Transverse Ranges).

Tectonic nappes and horizontal layering of the Earth's crust in the Mediterranean belt (Carpathians, Balkanides and Caucasus)

Abstract The morphological and kinematic features and mechanism of nappe formation of the pre-Alpine and Alpine tectonic nappes of the Carpathians, Balkanides and Caucasus are discussed. Detached basement nappes, cover nappes and ophiolite (obduction) nappes are distinguished. All detached nappes are shown to be genetically compressional, squeezed out as a result of tangential compression at depth accompanied by active underthrusting of the autochthone under the allochthone (Amstutz-type subduction). Ophiolite nappes are formed by squeezing out of oceanic crust and the occurrence of bilateral or unilateral obduction simultaneously with subduction. This formation of ophiolite nappes is a very transient process (occurring at lightning speed in the geological sense) compared to subduction. Data on large horizontal displacements at various levels in the crust entirely confirm the idea of a proposition that horizontal crustal and lithospheric layering, has recently been substantiated by geophysical data too.

Integrating Geologic and Economic Data Using a Geographic Information System (GIS): Offshore Gulf of Mexico

A comprehensive data base consisting of graphical elements with associated attribute values has been compiled for the Gulf of Mexico. These geographically registered data, obtained from federal, state, third party, and company sources, consist of economic, past and present hydrocarbon production, and geologic information. Data representing man-made features such as pipelines, offshore drilling structures, terminals, and ship channels were evaluated with water depth and coastline proximity to estimate cost/risk factors of oil exploration and production. Hard production data and soft data including estimates of oil maturity, undiscovered hydrocarbons, fault timing, and time of oil generation were likewise geographically registered with federal and state lease blocks. All attribute data were compiled at the well, field, and tract level in a company-standard relational data base for estimation of play boundaries, recoverable reserves, and valuation of bid strategies. Conventional 2-D GIS technology in a relational environment enhances the evaluation of available data for assessing hydrocarbon potential on a unit by unit basis. These analyses provide the input for true 3-D reservoir evaluation in the geological sense and with registered economic data, provide cost versus return estimates for any 3-D volume, given some known error.

<strong>Origins of Neotropical Leafy Hepaticae</strong>

The neotropical hepatic flora, predominantly constituted by members of the Jungermanniales and Metzgeriales, includes a disproportionate number of genera which are endemic (over 38) and a number which evidently originated here but have shown slight and in a geological sense, modern dispersal by solitary species. Endemism is confined almost to the Jungermanniales; it is to a large degree of a unique sort: confined to highly apomorphic derivatives, often extremely reduced, sometimes confervoid or thalloid (aside from ‘normal’ sexual branches). These endemics are derivatives of basically cool-Gondwanalandic suborders, chiefly Lepidoziineae and Cephaloziineae which, in the Antipodes today include a wide range of plesiomorphic taxa. The highest proportion of endemic genera, often stenotypic (1-3 species each) occurs in the upper montane zone: from upper Andean forest to páramo, to the edge of permanent snow and ice; a smaller number occurs at upper elevations of the Guyana Shield, but more occur in the riverine systems that dissect this shield. The taxa found there (i.a., Zoopsidella, Pteropsiella, Schusterolejeunea, Cephalantholejeunea) are among the most apomorphic of all hepatics.

Saying the Phenomena

This book' has been an unconscionable time arriving. I first heard tell of it a decade ago as an Oxford undergraduate; rumours of its imminence (in that geological sense of imminence peculiar to academic publishing) reached me while a student in Cambridge a couple of years on; and I saw samizdat pages from some of its parts a little later still (when, I was reliably informed, it was virtually in the press). And, so I discovered, the saga of the Great Work on Herophilus had been going on for a good deal longer than that. All that was at least five years ago for a while it seemed as though the rest was going to be silence (although by this time, naturally, the book was turning up in various bibliographies as 'forthcoming'; usually, infuriatingly, with titles different from that under which it finally forthcame). So, when Heinrich von Staden himself assured me a couple of years ago, while sipping a beer on a Madrid pavement at an unofficial and hence particularly pleasant session of a conference on Galen, that the book's debut was indeed only a matter of months away, it is perhaps understandable that I viewed this assurance with a certain scepticism. But it has come out at last: and the wait has been worthwhile. This is, quite simply, a magnificent piece of work; ground-breaking and painstaking scholarship combined with judicious interpretation and an enviable knowledge of the vast corpus of ancient medicine to create something which is in the best sense of the word definitive. We will not need another edition of Herophilus for a long time to come.

Flexural uplift of rift flanks due to mechanical unloading of the lithosphere during extension

We suggest that the uplift of rift flanks results from mechanical unloading of the lithosphere during extension and consequent isostatic rebound. This mechanism is presented as an alternative to explanations for rift flank uplift involving thermal or dynamic processes, and magmatic thickening of the crust. Our hypothesis is based on two critical concepts. First, the lithosphere retains finite mechanical strength or flexural rigidity during extension. Second, isostatic rebound (uplift) of the lithosphere follows when the kinematics of extension produces a surface topographic depression that is deeper than the level to which the surface of the extended lithosphere would subside assuming local isostatic compensation. We develop and analyze two kinematic models for instantaneous extension of the lithosphere to show that flexural rebound is a viable explanation for the uplift of rift flanks. We first investigate the isostatic consequences of finite simple slip on an initially planar, dipping normal fault cutting the entire lithosphere. When the lithosphere retains flexural rigidity during extension, the topography resulting from this model resembles a half graben, and the footwall rift flank is flexurally uplifted. This simple normal faulting model explains free‐air gravity anomalies and topography observed at rift flanks in oceanic lithosphere (such as Broken Ridge in the eastern Indian Ocean, the Caroline ridges‐Sorol Trough in the western equatorial Pacific, and the Coriolis Trough behind the New Hebrides island arc). We then investigate a general kinematic model for lithospheric extension where simple slip on a surface of arbitrary shape is accompanied by pure shear extension in the upper and lower plates. When the simple slip component is not zero or the distribution of pure shear in the upper and lower plates is not identical, the surface of slip can be regarded as a detachment. By simplification, our general model accounts for pure shear extension of the lithosphere that is uniform with depth. In this case, detachments have no meaning in the geologic sense. However, the kinematics of depth‐independent pure shear may nevertheless be described in terms of a surface, which we term a kinematic reference surface, at some depth in the lithosphere. We speculate that the depth of this surface may be rheologically controlled. The magnitude of rift flank uplift by flexure depends critically on the depth of this reference surface. In contrast, if local isostasy is assumed when the lithosphere undergoes a given amount of depth‐independent pure shear, the resulting topography will be the same regardless of how the kinematics of that extension are formulated. The basin and rift flank topography and free‐air gravity anomaly over young continental rifts, such as the Rhine graben, can be satisfied using our general extensional model with a small amount (<5 km) of extension along a listric‐shaped detachment soling into the crust‐mantle boundary. Because the flexural rebound mechanism explains the observed topography and gravity anomaly over both oceanic and continental extensional domains, we suggest that rheological differences between the two lithospheric types may not be important in their overall response to extension.

A different perspective on glauconite as a chronometer for geologic time scale studies

There are advocates of the use of glauconite as a chronometer for geologic time scale studies who insist that if the geohistory of the sample in question is known in detail, one can ascertain before hand that the sample will yield a radiometric result that is accurate in the geological sense. Examples are presented indicating that while some glauconite samples may yield the correct age within their assigned analytical uncertainties when compared to high‐temperature minerals, others clearly do not and are too young by varying degrees. The outright acceptance of published results on glauconite can result in erroneous age estimates of various biostratigraphic levels and stage or epoch boundaries.

CHANGE IN FINANCIAL INTERMEDIATION IN THE UK

The British financial system is experiencing change unprecedented in its scope and pace. Before the war Britain's financial structure was clearly dominated by the banks. Other types of institution had developed over the previous century and more, but their effect on financial conditions was not yet judged significant enough to be given even a passing mention in the Macmillan Report of 1931, for example. By the time of the Radcliffe Report of 1959, the increasing variety of institutions had been acknowledged; but the Radcliffe Report was still able to speak of faults, in the geological sense, which were difficult for borrowers to cross (Para 319).

GEODYNAMICS AND PETROLEUM FORMATION IN THE SEDIMENTARY BASINS OF SOUTHEAST ASIA

An interesting overview of the region is presented, emphasizing some aspects not usually considered by Western geologists as closely involved in petroleum generation. Southeast Asia corresponds in the geological sense to the Indo-Pacific region, which has a unique variety of structures, the formation of which was determined by processes in the boundary zone between the Eurasian and Australian cratons and the pacific and Indian thalassogens. The most recent published sources of geological and geophysical information are reviewed to provide a model for the formation of the sedimentary basins in craton-thalassogen boundary zones. 15 references, 2 figures.

On the Relationship between Regional Geomorphology and Lake Morphometry—A Swedish Example

The purpose of this work has been: (1) to collect data on certain lake morphometrical characteristics (area, volume and maximum depth) and geomorphological provenance from as many lakes as possible throughout Sweden, i.e., to establish a geomorphological lake register, and (2) to test a working hypothesis concerning a quantifiable relationship between lake morphometry and lake surroundings. Presently, the register includes 1060 lakes. The working hypothesis has been verified by means of a cluster analysis. The results include a new division of Sweden into five regions with lakes of similar morphometry. These results may, e.g., be used to statistically determine the most probable, 'normal', values of lake volume, mean and maximum depth, lake form and percentage area of lake bottom dominated by processes of erosion and transportation, from knowledge of lake area alone. Introduction Sweden has over 100 000 lakes. No one could give a precise figure because there are no exact definitions what is a lake, a pool, a pond or a river lake. Moreover, it could never be a definite figure because lakes undergo a characteristic lifespan: creation-youth-maturity-old age-extinction. This development is generally very slow and difficult to notice by individual standards in spite of the fact that lakes are often created both rapidly (in a geological sense) and drastically by endogenic and exogenic and, nowadays, anthropogenic forces. Lakes are unevenly distributed on the earth and are most abundant in areas affected by glacial activity (Hutchinson, 1957). Few parts of the world have more lakes than Scandinavia, which is demonstrated by Fig. 1 illustrating the distribution of lakes in Sweden. The morphometry largely determines the limnological, sedimentological and hydrological character of the lake, and lakes are often important integral parts of the ecosystem (cf. Wetzel, 1975). They are also sometimes the cause of conflicts, and different interest groups have different ideas and demands concerning the use of lakes and other bodies of freshwater as natural resources (cf. Franco and Wetzel, 1983). Presently, the prerequisites for aquaculture are under debate in many industrialised countries (Ackefors, 1982). Aquaculture. as agriculture, requires knowledge of natural functions and mechanisms so that adequate plans can be worked out and the possibilities for misuse minimized. Aim of the work The objective of this work is to test a working hypothesis whether there exists a quantifiable relationship between the lake surroundings, in this case the geomorphology, and the lake morphometry. To test this, data were collected from as many lakes as possible throughout Sweden on certain morphometric characteristics as well as on geom phological regions. This has been an arduous task which started in 1980. A more comprehensive report has been published in Swedish (Hakanson et al., 1983). This paper is intended to summarize some results and ideas of, hopefully, mo e general interest. Thus, we will only briefly discuss methods and possible future ways of utilizing these results in lake management and planni g. The focus here is on the working hypothesis and the general approach behind it. The ultimate idea underlying the work is to try to present a method that enables the determination of typical, characteristic lake morphometric features in different geomorphological regions; if the 'normal' morphometry can be determined objectively, then it would also be possible to quantify divergencies from the 'normal'. A comprehensive publication on Sweden's water resources has been presented by Falkenmark Geografiska Annaler * 66 A (1984) 1-2 103 This content downloaded from 157.55.39.163 on Wed, 21 Sep 2016 05:19:22 UTC All use subject to http://about.jstor.org/terms LARS HAKANSON AND BERT KARLSSON ATLAiS O£. stVEXtE _ SJ OAR LAKES Sant mman~,t~i[ av M6XGNUS LUI,NDQt:IST i .Al t xl{2: )00oo0i) ::o isO 14}E t.4i# ;

Reservoir Geology —A “New ” Role For The Explorationist

Abstract CANADA'S emergence as a producer of major oil occurred on February 13, 1947, just 36 years ago. A plaque commemorating that occasion can be viewed just a few miles south and east of the town of Devon, Alberta, a town which was created to service the Leduc - Woodbend area. Canada was still in a post-war recession, consequently, the promise of a new major industry spelled opportunity to a growing force of professionals, most world war II veterans, in both the earth sciences and in engineering. The main body surrounding this key group were Canadian geology graduates trained mostly in hard rock geology. Many graduates had geological engineering degrees but few, if any, were absorbed into the engineering departments of the major companies. Instead, they became part of the exploration teams where their hard-won engineering training was all but forgotten. On the other hand, engineering departments sought out mostly chemical and petroleum engineers, together with a smattering of mechanicals and engineering physicists for their future reservoir management teams, whose geological training was at best rudimentary. It is not surprising, therefore, that the technical forces driving the industry were split into two diverse factions-explorationists on the one hand, production and engineering on the other, with little common language and very different goals. Exploration philosophy has traditionally required a broad knowledge of sedimentation processes to develop geological trends favorable for accumulation of petroleum. When augmented with geophysics, source-rock analysis and a study of subsurface fluid systems, chances were good that sooner or later it would lead to a major discovery. Having made his mark, the explorationist was more than willing to relinquish control of follow-up drilling to the engineer, with little interest in the detailed geology of the reservoir. The engineer has traditionally made his reputation in two ways; first by getting wells on production as cheaply and efficiently as possible, secondly by devising new schemes for enhanced recovery. These objectives are not always compatible. In cutting front-end costs, false savings were often made, reducing the amount of coring, a basic geological tool. By the 1960s, more sophisticated petrophysical well logs were introduced, resulting in even more drastic reductions in core data. In some areas coring was cut out but not replaced by comprehensive logging programs. Also in the 1960s, the reservoir engineer was presented with a powerful new tool the digital computer for multi-dimensional, multi phase reservoir simulation. It was then possible to "model" the reservoir, match the production history. (If the reservoir was relatively simple), usually by adjusting the permeabilities. With a good model he could determine the most efficient plan for future reservoir management. Geological input to simulation models came much later, in the 1970s, when it was realized that no amount of number-crunching, (a.k.a. massaging of data), :could make certain models work, unless I they made geologic sense. Meanwhile, where was the geological expertise necessary to fill this gap? Production geologists, working under engineers, had been utilized mostly for generating net pay and structure maps for volumetric estimates, usually with little or no regard to internal reservoir geometry.

The corrugation of the galactic layer

The 21-cm line intensities in a (Z, R) distribution is studied at the locus of tangential points of the inner parts of the Galaxy using both Northern and Southern data. A corrugation effect is observed in the galactic neutral hydrogen layer with an average wave length of 2 kpc and a wave amplitude of 70 pc. The patterns obtained for the I and the IV quadrant indicate that the inner and the outer parts of the spiral arms are located, respectively, below and above the galactic plane. Also, with high angular resolution the corrugation pattern suggests the existence of ‘faults’ in a geological sense in the inter arm zones.

Liquid Immiscibility in Silicates

THE occurrence of liquid immiscibility in silicate melts has been established experimentally since 1927 (ref. 1). The compositions of the liquids are extreme in a geological sense and are found only at very high temperatures. These and other considerations2 have precluded any serious advancement of theories using liquid immiscibility as a possible explanation for the generation of different magmas.

Review of Salt Tectonics in Relation to the Disposal of Radioactive Wastes in Salt Formations

The plastic deformation of salt formations is reviewed to evaluate the possibility of diapiric processes affecting salt beds used for radioactive waste disposal. In a geological sense, rock salt is characterized by a marked mobility as a result of its ability to deform under relatively low stresses. Examples are known of salt formations deformed by tectonic forces, but the typical diapiric processes are essentially due to gravitational forces. In the initial phase, salt deformation is caused by differential loading of the salt bed; only after salt flowage has resulted in thickening of the low pressure zones of the salt bed does the density difference between salt and sediment contribute to the deforming stress. Salt diapirs are usually large structures, and to furnish the necessary large volume of salt, a mother bed of great initial thickness must be presumed. No minimum depth seems to exist for the plastic deformation of salt; however, the plasticity of salt increases with depth as a result of the increasing temperature. The rate of salt deformation is critical in relation to the required containment time for plutonium-contaminated waste. A few authors maintain that diapiric processes proceed at a catastrophic rate, but the geologic literature indicates that most geologists believe salt diapirism to be a relatively slow process and geologic evidence seems to support strongly the majority view. It can be concluded that, in the final stage of salt intrusion, rates of diapir growth as high as a few millimeters per year are possible, and in the initial phase of plastic deformation of the salt bed, flow rates should be markedly lower. In relation to the safety of radioactive waste containment, the risk of excessive deformation can be kept acceptably low if the disposal formation meets the following requirements: (1) bedded salt located in a geologically stable area; (2) subhorizontal salt beds exposed to very limited differential loading; (3) thickness of the salt beds of the order of 100 to 300 m; and (4) depth of the salt beds between 300 and 700 m.

Appraisal of Computer Mapping Techniques as Applied to Miocene Formations of Bayou Carlin and Lake Sand Fields, Southwestern Louisiana: ABSTRACT

A computer-aided subsurface mapping program of the middle Miocene section (-9,500 to -15,000 ft) was attempted for a 160-sq mi tract in the structurally low part of the famous Five Islands trend of Louisiana. Seven resistivity features were picked from most of 136 electric logs and were correlated and used to make one isopach map, and conventional (manually contoured) structural maps of 4 zones. The same data were then employed to generate computer maps by 2 different approaches: weighted-moving-average (contour maps) and least-square-fits of polynomial surfaces up to the fifth order (trend maps). Numerous computer maps were generated on the high-speed printer and plotter, including structural maps, isopach maps, trend maps, and various residual maps. However, all of them do not appear to convey geologic sense, and some, particularly high-order trend maps, may be of little use. The degree of similarity the computer maps bear with the manual maps varies widely with the map type and technique used. The contour-type maps may best serve as quick-look maps, bringing out the major structural elements and guiding the choice of horizons for hand contouring. Others, such as the isopach maps, yield the growth-fault effect and can guide later interpretations. The polynomial surface maps depict regional trends which can be used to make predictions away from known areas, to suggest highs and lows of significance, and to display meaningful thickness variations. The residual maps show promise of distinguishing structural traps, the locale of growth faulting, and typical tectonic and sedimentational patterns. Computer maps do not supplant manually contoured maps. Some of them, if used early in a mapping program, could aid in picking horizons for hand contouring and could be used as a guide for contouring. Others should be used to suggest corrections in the structure, and still others as guides to the final interpretation. End_of_Article - Last_Page 1900------------

Magneto-Telluric Experiments in Northern Ellesmere Island

Summary During the 1963 field season, a magneto-telluric experiment was successfully undertaken at and near Alert, in northern Ellesmere Island. Analysis of the results shows that the electric field is very strongly confined to a direction nearly N-S, that a strongly inhomogeneous or anisotropic situation exists with the electric field in phase (±5°) with the horizontal magnetic field for periods between 240 and 6000s, and that the electric to magnetic field ratio is constant and very small (0.12(6)m V km-1γ-1) in the same period range. At Lake Hazen, 150km to the SW approximately, the experimental data is of poorer quality, but the inhomogeneity or anisotropy is weaker, the mean direction of the electric field between 20 and 30° E of N, the phase advance of the electric over the magnetic field nearly 45° and the electric to magnetic field ratio is frequency dependent. The magnetic variations measured at Lake Hazen suggest an extension along strike of the Alert anomaly. The Alert results are not consistent in inhomogeneity, phase and frequency dependence with earlier models used to explain the magnetic variation anomaly observed in northern Ellesmere Island. Equally an interpretation of the magneto-telluric results in terms of a near surface plane conductor with a very large height-integrated conductivity ≅6(.3) × 10-6 emu is not consistent with the earlier magnetic variation results, fails to explain the inhomogeneity or anistropy, and makes no geological or common sense. The inductive situation is very complex and it appears that boundary arguments must be very important and need theoretical elucidation. At the present time no self-consistent hypothesis can be derived: some of the problems in deducing one are demonstrated in the text using illustrative calculations.

Consolidation characteristics and related properties of sediments from experimental mohole (Guadalupe site)

‘Consolidation’ in the geologic sense is the hardening, or lithification, of a sediment; in the field of soil mechanics consolidation refers to the reduction of volume of a sediment under imposed loads. Consolidation tests were run on eleven samples from the Guadalupe Mohole site, including surface samples from gravity cores (taken in the usual manner by lowering a weighted tube from the ship) and cored samples to a depth of 136 m (from the drilling operation). Interpretation of the test curves of these seriously disturbed samples indicates that these deep-sea sediments are stronger than might have been anticipated. They appear capable of supporting overburden pressures without significant reduction of porosity in the depth range studied. Porosities at the sediment surface were about 80%; in situ porosities for the deepest samples were estimated to be about 72%; reduction of no more than 5% owing to overburden pressure is estimated for the deepest sample (168 m). It is concluded that these effects are due to low rates of deposition, great age, and materials which induce interparticle bonds having the nature of chemical cementation.

Soils, Paleosols, and Soil‐Horizon Nomenclature

AbstractExhumed paleosols commonly occur geographically juxtaposed to modern soils. Use of standard soil‐horizon nomenclature, with its inherent genetic bias, may erroneously portray the histories of the juxtaposed pedo‐geologic soil landscapes. It is suggested that the nomenclature of exchumed paleosols be differentiated from the nomenclature of modern soils by insertion of an upper case P preceding the letter designations of the soil horizons of exhumed paleosols. Application of the proposed nomenclature is illustrated.Lithologic discontinuities of parent materials in which a solum has developed now is designated nomenclaturewise by the use of the subscript u—meaning unconformity. This is a misuse of the term unconformity in the geologic sense. In most cases the superposed parent materials are related conformably rather than unconformably. The vertical sequence of Roman numerals to indicate changes in parent materials, suggested by the Committee on Soil Horizons, adequately handles the problem. Application of the sequence is illustrated.