Showing papers in "The Journal of Geology in 1950"
TL;DR: Some types of graded bedding, especially minor or isolated occurrences and varved "clays," can be readily accounted for by normal processes of sedimentation as discussed by the authors, such as volcanic eruptions, dust storms, annual and longer climatic rhythms, rejuvenation of relief at the source or filling in of the sedimentary basin, churning up of sediment by storm waves, are among the more obvious potential causes of graded deposits.
Abstract: Some types of graded bedding, especially minor or isolated occurrences and varved "clays," can be readily accounted for by normal processes of sedimentation. Volcanic eruptions, dust storms, annual and longer climatic rhythms, rejuvenation of relief at the source or filling in of the sedimentary basin, churning up of sediment by storm waves, are among the more obvious potential causes of graded deposits. But the majority of occurrences cannot be explained by any of these processes. The authors believe turbidity currents of high density may be invoked to have supplied the sediment and deposited it in graded beds. The absence or insignificance of current bedding and ripple marking in graded deposits, the deposition of coarse material on the unconsolidated fine-grained top of the preceding bed, the enormous extent of each individual member without apparent change in thickness or character, and the frequent inclusion of angular fragments (even composed of clay) and of redeposited fossils are among the chief c...
502 citations
TL;DR: In the presence of water vapor under pressure, soda and potash feldspar crystallize readily from their glasses as discussed by the authors and form a complete series of solid solutions showing continuous variation of lattice-spacing as measured by X-rays.
Abstract: In the presence of water vapor under pressure, soda feldspar and potash feldspar crystallize readily from their glasses. At high temperatures they appear to form a complete series of solid solutions showing continuous variation of lattice-spacing as measured by X-rays. Studies of the dry melts had indicated that the solid solutions are of the type having a minimum-melting mixture. This conclusion is reinforced upon investigation in the presence of water. At a pressure of $1,000 kg/cm^{2}$ of water vapor the minimum lies at the composition 70 per cent $NaAlSi_{3}O_{8}$, and the temperature is 843° C. This temperature is 220° below that observed in dry melts, the lowering being induced by the presence of some 7.5 per cent $H_{2}O$ in the liquid phase or melt. Increase of pressure to $2,000 kg/cm^{2}$ produces a further lowering of only about one-third as much. When crystallized at still lower temperatures, the complete solid-solution relation no longer obtains, and two feldspars form side by side. Homogeneo...
212 citations
TL;DR: In this article, the controversial issue as to whether or not certain structures in the Niagaran of the Great Lakes region are true reefs is reviewed, and the biologic affinities of the common builders, combining frame-building and sediment-binding abilities, remain to be determined.
Abstract: The controversial issue as to whether or not certain structures in the Niagaran of the Great Lakes region are true reefs is reviewed. Reefs are defined in terms of fundamental biologic potentials of the organisms responsible for them rather than in terms of the present-day appearance of the structures. These potentials are the ability to erect rigid topographic structures by frame-building, sediment-retention and binding, and to create a wave-resistant structure. These have been the basic properties of reef-building biota throughout all time. Organisms potentially capable of erecting the Niagaran structures are shown to have been present. Evidence of their performance capacity is presented. The biologic affinities of the common builders, combining frame-building and sediment-binding abilities, remain to be determined. Stromatoporoids performed these functions in some cases. The character of the niche-dwelling assemblage is reviewed in terms of environmental relations and potential source material for bioc...
201 citations
TL;DR: In this article, an unbroken series of solid solutions between these alkali feldspars with a minimum on the melting and freezing curves at 1,063^{\circ} \pm 3^{circ} C$$ was shown.
Abstract: A study, of the alkali-feldspar join $$KAlSi_{3}O_{8}-NaAlSi_{3}O_{8}$$ in the system $$NaAlSiO_{4}-KAlSiO_{4}-SiO_{2}$$ shows an unbroken series of solid solutions between these alkali feldspars with a minimum on the melting and freezing curves at $$1,063^{\circ} \pm 3^{\circ} C$$. at 35 weight per cent potash feldspar. All alkali-feldspar compositions with more than 49 weight per cent potash feldspar melt incongruently and have leucite crystals present, which disappear only at higher temperatures. A revised equilibrium diagram for the system $$NaAlSiO_{4}-KAlSiO_{4}-SiO_{2}$$ is given; the data on which it is based will be published in full later.
139 citations
TL;DR: The contemporary and Pleistocene coral reefs of the Australian shelf regions illustrate reef development in a relatively stable epicontinental environment-the most common facies in geology.
Abstract: The contemporary and Pleistocene coral reefs of the Australian shelf regions illustrate reef development in a relatively stable epicontinental environment-the most common facies in geology. All reef forms-fringing, barrier, atoll, and platform reefs- and five varieties of coral island are found here. The vertical distribution of corals is controlled mainly by light, a function of turbidity, and the areal distribution mainly by temperature (minimum is about 18° C. average for the coldest month). The shape of coral reefs is generally controlled by wind, wave, and current, although complex forms due to old geomorphologic or structural controls later modified by wind, etc., are also common. Normally, a small reef patch, in a region of a single dominant wind and current, will grow into a horseshoe form, then to an atoll, and will eventually fill up to become a large platform. Coral islands are due either to accumulation of sand or shingle, in which case they tend to have an oval or streamlined shape, or to a R...
129 citations
TL;DR: In this paper, it was shown that Mallard's hypothesis can be excluded, although it has been suggested that this difference is due to a different degree of order-disorder between the Si and the Al atoms, triclinic microcline having a greater degree of ordering than monoclinic orthoclase (Barth's hypothesis).
Abstract: The literature on potash feldspar (including the modern textbooks) gives one the impression that, within the limits of observation, the several varieties of KAlSi3O8 have the same apparent lattice "symmetry" (α and γ of microcline being quoted as 90° within the limits of ±10′). Two principal opinions exist to explain the different modifications: (1) The atomic arrangement (structure) of all potash feldspar is the same, and this structure is triclinic. The differences in optical behavior are explained by differences in the size and shape of twinned portions in the material (Mallard's hypothesis). (2) Two different modifications of potash feldspar exist: triclinic microcline and monoclinic orthoclase. It has been suggested that this difference is due to a different degree of order-disorder between the Si and the Al atoms, triclinic microcline having a greater degree of order than monoclinic orthoclase (Barth's hypothesis). In this investigation it is shown that Mallard's hypothesis can be excluded, although...
92 citations
TL;DR: In this article, high and low-temperature modifications of albite are shown to have X-ray and optical properties different than those of the very pure natural albites from pegmatites, but these natural albits can, by heating, be converted into a form identical with the synthetic product.
Abstract: Synthetic albite is found to have X-ray and optical properties different than those of the very pure natural albites from pegmatites, but these natural albites can, by heating, be converted into a form identical with the synthetic product. High- and low-temperature modifications of albite are thus indicated. The inversion temperature is believed to be in the neighborhood of 700° C. Optical and X-ray studies show that the inversion extends into the plagiocla.se series approximately to $$An_{35}$$. These high-temperature plagioclases are common as phenocrysts in extrusive rocks but have not been found in plutonic rocks.
88 citations
TL;DR: The best known of the larger Permian barrier reefs of the Southwest, the Capitan as discussed by the authors, is described in detail in the paper as discussed by the authors and the sedimentation and depositional environment of this well-known reef.
Abstract: The Capitan is the best known of the larger Permian barrier reefs of the Southwest. This paper describes the sedimentation and depositional environment of this well-known reef.
66 citations
TL;DR: In this paper, the stability of grossularite has been investigated in relation to the progressive metamorphism of a limestone containing clay impurities, and the range of stability has been outlined indirectly from field and laboratory data.
Abstract: Exploratory experiments have been conducted to determine the stability range of grossularite garnet, $$Ca_{3}Al_{2}(SiO_{4})_{3}$$ Grossularite probably has a field of stability at atmospheric pressure; although the garnet does not require pressure for its formation, pressure should favor its formation. Grossularite may form by reaction of its components in the solid state; the intermediate products obtained are presumed to be meta-stable. The majority of garnets described as grossularite are probably members of the hydrogrossular series as defined by Hutton. Pressure, in addition to temperature and time, determines the stable member of the hydrogarnet series. It is believed that the dry end member, grossularite, exists but that it cannot exist in the presence of water at elevated temperatures. The range of stability of grossularite is outlined indirectly from field and laboratory data in relation to the progressive metamorphism of a limestone containing clay impurities. Grossularite has, as yet, not been...
59 citations
TL;DR: In this paper, the use of these substitutions as a means of obtaining information on the feldspars is discussed, and the principal aims of this line of investigation is to obtain information on substitutional disorder in alumino-silicates.
Abstract: Compounds of gallium and germanium isostructural with the feldspars have been prepared, and some of their crystal-chemical properties are here described. In the Na and K feldspars, $$Al^{+++}$$ and $$Si^{++++}$$ can be completely replaced by $$Ga^{+++}$$ and $$Ge^{++++}$$; but, in pure Ca feldspar, complete substitutions cannot be made. The use of these substitutions as a means of obtaining information on the feldspars is discussed. One of the principal aims of this line of investigation is to obtain information on substitutional disorder in alumino-silicates. It is difficult to locate specific positions of Al and Si atoms in many silicates because of the approximately equivalent X-ray scattering power of these two atoms. The use of a heavier-element replacement should produce more definite information on the degree of substitutional disorder, and it is hoped that these Ga and Ge feldspars will help in the interpretation of some of the problems of the natural minerals.
55 citations
TL;DR: The formations of central and east-central Vermont are exposed as a series of parallel belts that strike nearly north as discussed by the authors, and the distances from the base of the lowest formation to the top of the highest, measured normal to bedding, is more than 100,000 feet; this large apparent thickness is believed to be not very much greater than the original thickness.
Abstract: The formations of central and east-central Vermont are exposed as a series of parallel belts that strike nearly north. Most of the rocks dip steeply, and many are overturned. With one possible exception, there seem to be no major repetitions within the sequence, and the order of formations from west to east appears to be the same as the order of their deposition. The formations are dominantly schist or phyllite, with varying proportions of arenaceous material. One thin formation, the Shaw Mountain, contains quartz conglomerate, calcareous tuff, and crinoidal limestone. The third-from-highest formation, the Waits River, is very thick and contains a large proportion of calcareous beds. The distance from the base of the lowest formation to the top of the highest, measured normal to bedding, is more than 100,000 feet; this large apparent thickness is believed to be not very much greater than the original thickness. The metasediments have been intruded by granitic dikes and plutons, mafic dikes, and small ultr...
TL;DR: A composite reef is a composite reef made up of a number of distinctive reef types-windward reefs, leeward reefs, and lagoon reefs as discussed by the authors, which is the source of all the materials that make up an atoll.
Abstract: An atoll is a composite reef made up of a number of distinctive reef types-windward reefs, leeward reefs, and lagoon reefs. Most of these are zoned relative to prevailing winds and currents. Organic growth, erosion, and deposition of sediment influence each of these zones, but in each the balance of forces operating at the present time may be roughly appraised. Some reef zones appear to be making headway against the sea, others appear to be essentially in a state of equilibrium, while still others are being eroded. Organic growth is the source of all the materials that make up an atoll. Some of the skeletons of the reef-building organisms remain in position of growth after death, but a much larger proportion are broken up by physical and organic agencies to form sediments that are deposited on the seaward slopes or in the lagoon. So long as organisms live on an atoll, it continues to grow, but it grows mainly by the accumulation of clastic sediments.
TL;DR: The down-structure method of looking into maps rather than at them can be introduced into the most elementary exercise in geologic map interpretation; it helps the student to grasp quickly the structural significance of patterns on maps made by others and increases his sensitivity in laying down lines on his own maps in the field as mentioned in this paper.
Abstract: Most contact lines on geologic maps are surface traces of inclined planes. If the map is viewed down the slope of these planes, it becomes, in effect, a section, and the map patterns are seen as structures. The "down-structure" method of looking into maps rather than at them can be introduced into the most elementary exercise in geologic map interpretation; it helps the student to grasp quickly the structural significance of patterns on maps made by others and increases his sensitivity in laying down lines on his own maps in the field. Used with proper caution and an understanding of its limitations, the method is applicable to a wide range of map patterns, from those of simple monoclinal structures to those of recumbent folds.
TL;DR: In this paper, the influence of grain size on variations in composition of thin sections was studied and it was shown that the trace of any grain dimension along a section of the grain will usually be shorter than the true dimen-
Abstract: In studying the influence of grain size on variations in composition of thin sections, I have recently retraced a path first marked out by Dr. Krumbein (1935) and wish to suggest here that his principal result is both a little easier to reach and a little more difficult to interpret than one would gather from his excellent essay. Krumbein points out that the trace of any grain dimension along a section of the grain will usually be shorter than the true dimen-
TL;DR: The authigenic minerals in the Oriskany, Berea, and Big Injun sandstones are quartz, calcite, dolomite, orthoclase, microcline, albite, chlorite, kaolinite, and pyrite as discussed by the authors.
Abstract: The authigenic minerals in the Oriskany, Berea, and Big Injun sandstones are quartz, calcite, dolomite, orthoclase, microcline, albite, chlorite, kaolinite, and pyrite. Most of the quartz grew in open spaces, but some replaced clastic calcite. Two stages of silicification occurred in parts of the Berea sandstone. Authigenic chlorite appears as fringes around the detrital grains or around the early quartz growths. Calcite occurs as secondary rims on clastic calcite and as a cementing material in the voids. Rhombs of dolomite occur in the interstices and as replacements of feldspar and the clayey matrix. Authigenic feldspar is present in the form of overlays around detrital grains. Secondary kaolinite occurs as an alteration product of feldspar and as a filling in many of the voids which remained after the crystallization of the other minerals. Most of the authigenic minerals formed after burial, because the secondary growths are generally free of strain and fill the cracks in fractured grains of mica and feldspar. The secondary calcite and chlorite probably formed from primary constituents in the sediments. Most of the silica was apparently derived from outside sources because little solution of quartz occurred at the points of contact between the detrita! grains.
TL;DR: Three ocean-bottom core samples were obtained from within the packice area in the mouth of the Ross Sea, Antarctica, during the U.S. Navy Antarctic Expedition of 1946-1947 as mentioned in this paper.
Abstract: Three ocean-bottom core samples were obtained from within the pack-ice area in the mouth of the Ross Sea, Antarctica, during the U.S. Navy Antarctic Expedition of 1946-1947. These cores consist of several alternations of glacial marine sediment and of fine-grained sediment which apparently is nonglacial. Age determinations of the material, made by Dr. W. D. Urry, provide a time scale on which the lithology may be plotted. Because the cores record periods of from one hundred and seventy thousand to over a million years, a record of the Pleistocene glacial history of Antartica is provided. A comparison of this with the record for the Northern Hemisphere indicates that glaciation was contemporaneous in the two hemispheres.
TL;DR: In this paper, the results of core drillings on Gotland in 1946 and 1947 led to a re-examination and revision of our conception of the reefs of Gotland, their structure, reef-building organisms, and appearance.
Abstract: Core drillings on Gotland in 1946 and 1947 led to a re-examination and revision of our conception of the reefs of Gotland, their structure, reef-building organisms, and appearance. A short report on the results of the investigation is submitted below. Of particular interest are the findings that calcareous algae play a considerably greater role as rock-formers than had been previously observed.
TL;DR: In this article, the lattice of "low" albite differs from that of high albite in that (010)$\Lambda$(100) changes from 90°30' to 88°15' and (010$\lambda $(001) from 86°20' to 86°0'.
Abstract: As shown in the accompanying paper by Tuttle and Bowen, two kinds of albite exist. They are distinguished by optical properties and differences in X-ray powder patterns. The generally known "normal" albite (called "low" albite in this paper) is one type, the other (here called "high" albite) can be obtained by heat treatment of "low" albite or by direct synthesis. This investigation deals with some of the "low-high" albite relations. X-ray investigations combined with optical measurements have been carried out. The optical measurements are similar to those reported by Tuttle and Bowen. Structural differences as revealed by the X-ray photographs are discussed. The lattice of "low" albite differs from that of "high" albite in that (010)$\Lambda$(100) changes from 90°30' to 88°15' and (010)$\Lambda$(001) from 86°20' to 86°0'. This lattice difference is accompanied by changes in intensities of the X-ray reflections. The structural differences, as far as they are expressed as intensity differences of the X-ray...
TL;DR: Triclinic adularia as discussed by the authors is a secondary modification of monoclinic Adularia and has distinctive optical behavior which establishes it as a variety of potash feldspar.
Abstract: Adularia traditionally has been described as monoclinic Sections of adularia crystals from several localities, studied on the universal stage, show optical orientations inconsistent with monoclinic symmetry The optical deviation from monoclinic symmetry is absent or very small in the cores of the crystals but increases toward the surfaces The optical orientation and axial angles of triclinic adularia vary from those of monoclinic adularia in the direction of sanidine rather than of microcline Triclinic adularia occurs as a secondary modification of monoclinic adularia It has distinctive optical behavior which establishes it as a variety of potash feldspar
TL;DR: The Wolf Creek Crater is the second largest crater of meteoritic origin to be discovered on the earth's surface as mentioned in this paper, having a maximum depth of 170 feet and 90 feet of broken rock forming the elevated rim.
Abstract: The Wolf Creek Crater is the second largest crater of meteoritic origin to be discovered on the earth's surface. The crater is circular, 2,800 feet in diameter, has a maximum depth of 170 feet and 90 feet of broken rock forming the elevated rim. Fragments of meteoritic iron were found around the rim. The age of the crater is considered to be Pleistocene or Recent.
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TL;DR: Johnson's complex theory of origin of the Carolina "bays" would violate the laws of conservation of energy, inasmuch as the assumed outflow of ground water would have to be the same as the area of intake as discussed by the authors.
Abstract: Since the area of the bays is almost the entire area of the coastal plain in the two Carolinas, Johnson's complex theory of origin of the Carolina "bays" would violate the laws of conservation of energy, inasmuch as the area of assumed outflow of ground water would have to be the same as the area of intake. Johnson assumed implicitly that the coastal-plain bedrock (chiefly Cretaceous) dips down the slope of the coastal plain toward the southeast in the manner of a textbook illustration of coastal plains, whereas the dip is actually toward the south or slightly southwestward. Therefore, his assumed "spring vents" should have moved northward under his theory, instead of northwestward, as the shape of the bays would require. Other errors of fact and examples of illogical theory in Johnson's spring-vent hypothesis are pointed out. Through a revision of the meteoritic theory it is shown that the supposed impact could have occurred at any one of several times in the geologic past.
TL;DR: The Lower Carboniferous limestones of northern England show two main facies, the distribution of which is related to the behavior of the floor on which the system rests.
Abstract: The Lower Carboniferous rocks of northern England show two main facies, the distribution of which is related to the behavior of the floor on which the system rests. Certain areas were relatively stable, and on these the clear-water massif facies was deposited. In other areas the floor subsided more rapidly, and muddy-water basin facies resulted. The reef facies is found at the margins of the massifs in narrow tracts between the two main types and at certain places within the basins. A twofold division is therefore made into basinal reefs and marginal reefs. The problems connected with the reef limestones include distribution, conditions of deposition, lithology and fauna, tectonics, and erosional history. The classic theories are summarized, and brief accounts are given of typical areas. The basinal reefs seem to have been formed as moundlike accumulations of organic debris, but marginal reefs have several origins. Their tectonic and erosional histories are examined. A feature common to all types is their...
TL;DR: A compound corresponding in optical properties and in X-ray powder pattern with the natural mineral sapphirine has been synthesized by repeated sintering of the constituent oxides at atmospheric pressure as mentioned in this paper.
Abstract: A compound corresponding in optical properties and in X-ray powder pattern with the natural mineral sapphirine has been synthesized by repeated sintering of the constituent oxides at atmospheric pressure. The most probable formula for this artificial compound is $$4 MgO\cdot5 Al_{2}O_{3} \cdot2 SiO_{2}$$. An unidentified crystalline phase previously noted in certain magnesia-alumina-silica porcelains has been shown to be identical with this synthetic sapphirine. There is reason to believe that sapphirine possesses a small field of primary crystallization on the liquidus surface of the ternary system $$MgO-Al_{2}O_{3}-SiO_{2}$$. Some revision of the earlier work on this system therefore appears to be necessary. Experiments designed to prove the existence of sapphirine as an artificial mineral and to determine its thermal behavior and its stability relations with other crystalline phases in the ternary system have been carried out. The results indicate that synthetic sapphirine melts incongruently at or nea...
TL;DR: In this paper, the authors discuss two examples of slump structures from Finland, one of which occurs at Aitolahti in the immediate neighborhood of the locality where J J Sederholm found his Corycium enigmaticum.
Abstract: In his paper, v Straaten (1949) discusses two examples of slump structures from Finland, one of which occurs at Aitolahti in the immediate neighborhood of the locality where J J Sederholm found his Corycium enigmaticum In v Straaten's opinion, the Corycium cannot be of fossil origin, inasmuch as it is more or less linked with the occurrence of slump structures He emphasizes the rarity of fossil remains of true algae without a skeleton of inorganic material, such fossils being generally restricted to derivatives of fine-grained sediments, whereas at Aitolahti the Corycium "occurs abundantly in coarse sandy beds, which often show slump structures or indicate considerable turbulence of the depositing water by crosslamination" (1949, p i6) The carbon content of the Corycium is high as compared with the content in freshly embedded algae, and this leads to a very improbable wall-thickness for the original living organism Moreover, v Straaten is unable to see how the compaction of the algal walls could have resulted in the formation of coherent sacs, because the carbonization of algae embedded in a sedi-
TL;DR: In this article, the mineralogy of rock phosphates is discussed in light of present limitations of knowledge of these minerals, and data are furnished on thirty-eight minerals that can occur in these rocks.
Abstract: Need for more extensive application of thin-section petrography to study of sediments, especially rock phosphates, is emphasized. The petrographic microscope alone is inadequate for investigation of these rocks, and often it will be necessary for the petrographer to employ X-ray diffraction, qualitative microchemistry, and other special methods. The mineralogy of rock phosphates is discussed in light of present limitations of knowledge of these minerals, and data are furnished on thirty-eight minerals that can occur in these rocks. A list of recently discredited species is also furnished, and several textures and microstructures are illustrated. The geochemical and mineralogical data on rock phosphates are regrettably meager. Theories on the origin of some of the primary, sedimentary rock phosphates cannot progress beyond the realm of speculation until the conditions which bring about precipitation of varieties of apatite from sea water have been more thoroughly investigated by laboratory techniques. Data...
TL;DR: The role of turbidity currents in sedimentation has not been understood and has been, in general, unappreciated by the study of the sedimentary deposits as discussed by the authors ; however, the work of Kuenen and Migliorini in this issue of the Journal, is therefore, a most significant contribution.
Abstract: The role of turbidity currents in sedimentation has not been understood and has been, in general, unappreciated. The paper "Turbidity Currents as a Cause of Graded Bedding," by Ph. H. Kuenen and C. I. Migliorini in this issue of the Journal, is therefore a most significant contribution to the study of the sedimentary deposits. Though turbidity currents have been known for some years, nobody seems to have examined the deposits made by these currents. Kuenen and Migliorini have done just this and have shown that these deposits have unique textures and structures by means of which they can be identified. Students of modem marine sediments should now re-examine carefully the coarser materials collected in their coring tubes. Graded beds are known to occur in soine cores and have even been suspected of being produced by turbidity currents (Bradley, 1940). That such deposits are common in some places seems highly probable. It may even be possible to determine from suitable cores whether the delta-like deposits at the mouths of some of the submarine canyons consist of truly fluviatile sediments or are the deposits of turbidity currents. It is even more important, now that the diagnostic features of the deposits made by turbidity currents are known, that the rocks of the geologic record be re-examined to determine whether or not they include such deposits. Such rocks, if they exist, will demonstrate the reality and measure the importance of turbidity currents as agents of sediment transfer in the geologic past. Until this is done, one cannot say that turbidity currents are nonexistent or unimportant. The observations of Migliorini are, therefore, most significant. Although the paper by Kuenen and Migliorini is concerned primarily with the problem of graded bedding, it sheds much light on the origin of the graywackes.2 In 1927 I began my studies of the Archean graywackes and slates of the Canadian shield. Ever since then I have
TL;DR: Extensive series of ripple mark at various horizons have been observed in Silurian rock salt of the Salina formation as mentioned in this paper, which is the first large-scale observation of ripple marks in rock salt.
Abstract: Extensive series of ripple mark at various horizons have been observed in Silurian rock salt of the Salina formation. Anhydrite lamellae which show similar ripple mark have been observed in the clear salt mass. These are the first large-scale observation of ripple mark in rock salt. The only other published observation was made in 1908 on small ripples in a rock-salt drill core of Permian age from the Zechstein in Hesse.
TL;DR: Wright and Priestley as mentioned in this paper classified ice-foot formations as follows: (i) the tidal platform ice foot, formed by tide action between high and low-water marks; (ii) the storm ice foot built up above high-water mark by spray from breaking waves; (iii) drift ice foot fabricated from drift and consolidated by sea water which surges through the tide cracks.
Abstract: Wright and Priestley (1922, p. 581), in their classic work on Antarctic glaciology, suggest the term \"icefoot\" for the ice formation which joins the land and sea ice between highand low-water marks. This is a glaciological feature of considerable geological importance, since, while it is fast to the beach formation, it affords complete protection against erosion. When it disintegrates, however, it becomes a powerful transportation agent, as masses of beach material are rafted away on the undersurface of the ice. Wright and Priestley classify ice-foot formations as follows: (i) the tidal platform ice foot, formed by tide action between highand low-water marks; (2) the storm ice foot, built up above high-water mark by spray from breaking waves; (3) the drift ice foot, fabricated from drift and consolidated by sea water which surges through the tide cracks; (4) the pressure ice foot, formed by overriding slabs of sea ice emplaced by an on-shore movement of the sea ice; and (5) the stranded-floe ice foot, incorporating beached \"bergy bits.\" Two additional types of ice foot are described below: the \"false ice foot\" and the \"wash-and-strain\" ice foot.