Brown Sand Research Articles

Persimmon Creek Field--Anatomy of a Morrow Stratigraphic Trap: ABSTRACT

Persimmon Creek field in T20N, R22W, Woodward County, Oklahoma, on the northern shelf of the Anadarko basin, produces gas and condensate from upper lower Morrow sandstone. The field occurs above a prominent southward-plunging structural nose on the Chester limestone. This and similar noses nearby appear to be paleotopographic highs that strongly influenced subsequent Morrow deposition. A thicker Morrow section overlies Chester lows or paleovalleys and a thinner sequence occurs above the noses. In this area, the Morrow contains an upper shale section and a lower sand-shale sequence containing four major sandstone units, each of which may contain one or more discrete sandstone beds with interbedded shale. The basal Morrow Hamilton sandstone strikes west-northwest, but filling of the subjacent Chester paleovalleys has caused local thicker sand accumulations with good porosity to trend north-south. The overlying Yellow sandstone has similar characteristics. In the Brown sandstone, this relationship is reversed, and the thickest sand accumulation and best porosity development occur above the plunging Chester noses. The uppermost Fritzler sandstone is more erratic in character, showing little relationship to Chester paleotopography. End_Page 641------------------------------ Persimmon Creek field, with an area of about 2 mi2, produces from north-south-trending Brown sand bars 8 to 20 ft (2.4 to 6 m) thick with 14 to 22% porosity. By analogy, in this part of the Anadarko basin, Morrow exploration should focus on locating porous upper lower Morrow sandstone above basinward-plunging Chester noses. End_of_Article - Last_Page 642------------

Sedimentary framework of the Potomac River estuary, Maryland

Analyses of seismic-reflection profiles, sediment cores, grab samples, and side-scan sonar records, along with previously collected borehole data, reveal the characteristics, distribution, and geologic history of the shallow strata beneath the Potomac River estuary. The lowermost strata are sediments of the Chesapeake Group (lower Miocene to lower Pleistocene) that crop out on land near the shore but are buried as much as 40 m below the floor of the estuary. The top of these sediments is an erosional unconformity that outlines the Wisconsinan valley of the Potomac River. This valley has a sinuous trend, a flat bottom, a relief of 15 to 34 m, and axial depths of 34 to 54 m below present sea level. During the Holocene transgression of sea level, the ancestral valley was filled with as much as 40 m of sandy and silty, fluvial-to-shallow estuarine sediments. The fill became the substrate for oyster bars in the upper reach and now forms most marginal slopes of the estuary. Since sea level approached its present position (2,000 to 3,000 yr ago), the main channel has become the locus of deposition for watery, gray to black clay or silty clay, and waves and currents have eroded the heterogeneous Quaternary sediments along the margins, leaving winnowed brown sand on shallow shoreline flats. Pb-210 analyses indicate that modern mud is accumulating at rates ranging from 0.16 to 1.80 cm/yr, being lowest near the mouth and increasing toward the head of the estuary. This trend reflects an increased accumulation of fine-grained fluvial sediments near the turbidity maximum, similar to that found in nearby Chesapeake Bay. The present annual accumulation of mud is about 1.54 million metric tons; the cumulative mass is 406 million metric tons.

Tungiasis in Travelers From Tropical Africa

TUNGIASIS is an inflammatory condition of the skin produced by the invasion of the pregnant female sand fleaTunga penetrans.1With the increased tourist trade to Africa, attention of travelers should be called to the existence of this parasite and the need for early therapy to prevent sepsis. We report five patients with tungiasis. Report of Cases An opportunity was presented recently to study a tour party of 19 women traveling to Africa to review native arts and crafts. The tour director mentioned the possibility of tungiasis in her general discussion of the health aspects of the trip. No one of the party gave a history of walking barefoot or even walking outside in the sand or dirt. The tour director informed the people that sheets hung outside and touching the ground were able to permit the brown sand fleas to spread into the bedrooms. Five of the 19

Fertilizer Studies with Groundnuts on the Brown Sands of Guyana. I. Effect of Nitrogen, Inoculum, Magnesium, and Fritted Micronutrients1

AbstractThe Brown Sands are a dominant soil group in South Guyana. They are coarse textured ‐ sand to sandy loam; highly leached; acid, and, although not naturally fertile, they appear suitable for large scale cultivation of groundnuts [Arachis hypogoea (L.)].Two experiments were conducted on these soils to determine the effect of fertilization and inoculation on crop performance.In the nitrogen × inoculum (Rhizobium japonicum) series, N did not influence yield. It caused a decrease in nodulation with the effect becoming more marked with constant cropping. Inoculum up to 226 g/27 kg seed increased yields but decreased nodulation only at the last of three plantings. Both Mg and fritted micronutrients had no effect on yields; these results were difficult to explain considering the highly leached nature of this soil.

Fertilizer Studies with Groundnuts on the Brown Sands of Guyana. II. Effect of Nitrogen, Phosphorus, Potassium, and Gypsum and Timing of Phosphorus Application1

AbstractThe effects of N, P, K, and gypsum and timing of application of P on the performance of groundnuts (Arachis hypogoea L.), grown on the Brown Sands of Guyana, were studied. Generally, 15 kg N/ha gave optimum production. However, in a dry season on the coarser textured soils and during all seasons on a finer textured soil 32 and 48 kg/ha of N were needed, respectively. Application of up to 30 kg P/ha increased yields on all soils found under savannah vegetation except the finest textured one. P did not increase yields of groundnut on the soil occurring under forest vegetation. Potassium within the range tested (124‐164 kg/ha) had no effect on yield. Application of up to 495 kg gypsum/ha increased yield and reduced the number of “pops.” Application of all the P at planting produced higher yields than when the application was split, and this effect was greater during periods of stress and at low rates of gypsum. Timing of P applications had no effect on the number of “pops.”Both P and K increased in all four soils with repeated applications of the respective fertilizers. The amounts accumulated however, were small relative to the quantities applied. Potassium accumulation increased with the clay content of the soils. Total N increased in two soils only.

Descriptions of new species and notes on taxonomy of New Zealand Mollusca, No.2

Abstract Four new species of Miocene and Pliocene Mollusca are described, in the genera Arca, Buccinulum, Nassicola and Colubraria. Arca cottoni Waghorn is recorded from several localities of Waipipian to Castlecliffian age and graphically differentiated from the new species. Ovicardium Marwick is ranked as a subgenus of Acrosterigma Dall and A.(O.) parki (Marwick) is synonymised with A.(O.) rossi, an excellent specimen of Eumarcia benhami Marwick is figured, Thracia magna Marshall and Murdoch and Calliostoma (Maurea) waiparaense Suter are recorded from the Nukumaru Brown Sand, “Modelia” nukumaruensis Laws is transferred to Calliostoma (Maurea), Cheilea cf. plumea Laws and Zemacies prendrevillei Marwick are recorded from Waipipian rocks, Kaiparathina Laws is transferred from the Janthinidae to the Trochidae, “Merica” haweraensis Laws is placed in Trigonaphera Iredale, and Aeneator contractus Laws is synonymised with Penion haweraensis Powell. A previously unrecognised shellbed member of the Waverley Forma...

Brown and Gray Sands on the Virginia Shelf: Color as a Function of Grain Size

Brown iron-staining on coarse shelf sands has been taken as evidence of subaerial weathering, either in the source area or at the depositional site. However, we note that iron-staining can occur subaqueously, as well. We have found a close correlation between grain size and color on the inner Virginia shelf, with finer sands being olive-gray, and coarser sands being brown. We suggest that the sand-grain surfaces are in chemical equilibrium with their environment. The coarser sands are permeable, and are kept oxygenated by wave surge. The finer sands are relatively inpermeable, and are reduced by interstitial organic matter. While in any given case, brown iron-staining may have occurred sub-aerially, it may also have occurred in the modern marine environment. Hence brown iron-staining is not a definitive criteria for a relict origin or subaerial exposure of shelf sand.

Paleoecology of a Pleistocene Microfossil Assemblage at the Fairlawn, Ohio, Mastodon Site

Thirteen species of ostracods and selected plant matter collected in a vertical section exposed at Fairlawn, Ohio, reflect progres- sively shallowing conditions in Pleistocene lake sediments. dentally discovered during the excavation of the basement of the Billows funeral home in Fairlawn, Ohio. The bones lay at a depth of approximately 3.5 m below ground level in a plastic black muck. Located on the western edge of a broad, shallow, roughly elliptical depression, approximately 400 by 800 m, the site is, situated in glacial outwash deposits of the Wabash moraine, in which several obvious kettle lakes are nearby. The stratigraphic section exposed by the excavations consists of a lower, well-sorted sand and gravel sequence, of glacial outwash origin, a middle varve-like sequence of thinly bedded gray silts and sands and black clays, presumably deposited in a kettle lake, and an upper sequence of massive brown sand, silt and clay containing root remains, probably laid down during the subaerial filling of the kettle depres- sion. Contact between outwash material and lake deposits dips rela- tiveTb steeply to the east and lake deposits thicken rapidly in that direction. The section sampled for microfossil remains consisted of 2.13 m of subaerial deposits and 5.23 m of lake sands, silts, and clays. The subaerial deposits and outwash sands were unfossiliferous, whereas the lake deposits contained a variety of ostracods, mollusks, and plant remains.

Erosional modification of a lateritized landscape over sedimentary rocks. Its effect on soil distribution

Erosional modification of a landscape, originally mantled by laterite, has been studied in the Perth Sedimentary Basin of Western Australia. A basis for understanding the soil pattern has thus been provided. This pattern depends on the variation in parent material resulting from the differential stripping of the lateritic mantle which in turn is related to a sequence of changes from a gently undulating upland to broad valleys. Yellow sands, derived by colluviation from the surficial horizons of the lateritic mantle, dominate the upland surface. Lower down yellowish brown and reddish brown sands, having as their source the deeper horizons of the laterite, occupy areas of increased relief. Along the sides of broad valleys, brown and dark red sands dominate areas downslope from ferruginous sandstone exposed as a consequence of even more effective erosion. The laterite mantle appears to have been developed in a landscape already showing relief including a system of valleys. Evidence suggests subsequent uplift. However, rejuvenation of the drainage system consequent on this has had only very limited influence on the area. Rather, it is to climatic fluctuation that erosional processes have responded. The magnitude of these processes is related to landscape features, notably the sequential changes up along this ancient valley system.

Prehistoric Springs and Geochronology of the Clovis Site, New Mexico

AbstractGeologic investigation and radiocarbon dating of a newly exposed stratigraphic section at the famous Early Man site of Blackwater No. 1 (Clovis) in eastern New Mexico show the Brown Sand Wedge to be in part a contemporaneous facies of the Diatomaceous Earth (10,000 to 11,000 years old) and in part older (11,000 to 11,500 years old). The Gray Sand is probably more than 12,000 years old. Artifacts contained therein are concentrated in the upper 6 in. and are believed to have intruded the sand via the tramplings of the surface by man and animals.The discovery of ancient spring-feeder conduits confirms the springhead origin for the Brown Sand Wedge and the Gray Sand suggested by Sellards and Evans (1960). In addition to well-sorted, nearly spherical, graded, quartz grains the conduits contained Clovis, Folsom, and Agate Basin artifacts bearing an extremely high polish. Some Agate Basin points appear to have been coeval with Folsom points; others are younger. Deposition of the Carbonaceous Silt containing Scottsbluff points, Frederick points, and points of the Portales complex began as early as 9,800 years ago, and possibly continued as late as 7,000 years ago.

Contribution a l'etude du Quaternaire des Idjibitene et de la bordure meridionale de l'Adrar (El Gletat, Mauritanie)

Abstract Two morphologically different regions are distinguished in the Quaternary of the Idjibitene mountains and along the southern border of the Adrar (El Gletat, Mauritania). Along the south and southwest border of the Adrar, deposits resulting from slope erosion are observed; to the south, dune structures and lake formations with white sands, brown sands, rare ferruginous crusts, and sand cemented by calcite (tarous) are seen. By observation of the terrain, collection of in place Acheulean industries, and study of the sands (granulometric and morphometric) it has been possible to reach an understanding of the stratigraphy. A chronology of Quaternary deposits of the Idjibitene is proposed. Close analogies with the Quaternary formations of Majabat are established.

Quaternary sedimentation in the Arctic ocean

A distinct boundary between sediment types usually occurs at a depth of about 10 cm in bottom cores raised from the Alpha Rise in the Arctic Ocean. The sediment between the tops of the cores and the 10 cm boundary is a dark brown, foraminiferal lutite mixed with ice-rafted sand and pebbles. The sediment between the 10 cm boundary and a depth of about 40 cm is a light brown sand with ice-rafted material but few Foraminifera. The 10 cm boundary apparently represents the most recent change in pelagic deposition in this region and must be connected with climatic changes. Foraminifera from a zone between 7 and 10 cm have been dated by the C 14 method as 25,000 ± 3000 and as 30,000 years BP in two different samples. The 10 cm boundary itself has been dated as 70, 000 years BP by a uranium series method. If these dates are accepted, a low sedimentation rate of 1 1 2 to 3 mm/1000 years is indicated for the Alpha Rise and for the Arctic Ocean as a whole if pelagic sedimentation has been uniform over the entire ocean. Cores from the Canada Abyssal Plain differ in character from the Alpha Rise cores consisting primarily of olive-gray lutite without Foraminifera or ice-rafted material. This sediment was probably deposited by turbidity currents. A 3 mm layer of dark brown, foraminiferal lutite occurs at the top of the Canada Abyssal Plain cores. This layer is similar to the upper layer in Alpha Rise cores and apparently represents continued pelagic deposition since the last turbidity current. Foraminifera from this upper 3 mm layer have been dated as 700 ± 100 years BP by the C 14 method. The conclusion is that pelagic sedimentation has continued unchanged in the Arctic Ocean from about 70,000 years ago to the present. This implies that the present ice cover has existed for that length of time.

Early Occupations in Bighorn Canyon, Montana

Excavation of the Mangus Site (24CB221) in Bighorn Canyon, Montana revealed a stratum containing artifacts of the Agate Basin Complex. This occupa tion was dated by radiocarbon at 6740 B. C. and 6650 B. C. The Sorenson Site (24CB202) contained two early cultural levels, one of unknown cultural affiliation datedat 5850 B. C. and 5610 B. C. over lying a second unidentified occupation. Future investigations in Bighorn Canyon may produce artifacts allowing identifi cation of these two occupations. Recent archeological salvage investi gations within the Yellowtail Reservoir of south-central Montana have brought to light several occupations of considerable antiquity. In 1962, the River Basin Sur veys of the Smithsonian Institution exca vated a small rock shelter containing evi dence of two occupations dating in excess of 7,000 years but of unknown affiliation. Subsequently, during the 1963 field sea son, artifacts of the Agate Basin com plex were found in a second shelter in the immediate vicinity. A comprehen sive report of these excavations is being deferred until all work in the reservoir area has been completed, but because of general interest in cultural remains of early date, this short, preliminary pa per is presented in order to make avail able two additional radiocarbon dates for the Agate Basin complex, brief de scrip tions of the associated features and arti facts, and data concerning the other ear ly occupations in Bighorn Canyon. The Mangus Site (24CB221), with which this report is primarily concerned, was a small rock shelter located on the left bank of the Bighorn River in Bighorn Canyon about seven airline miles north of the Montana-Wyoming state line in Car bon County, Montana. The shelter was about 55 feet wide and 19 feet deep and was situated at the top of a steep talus slope about 100 feet above the river. The northern end contained dense occu pational debris, but the southern end had a low ceiling and was very narrow, af fording little protected area for living. Three distinct cultural levels were de fined, the lowest of which contained Agate Basin points. The uppermost cul tural level was Late Prehistoric (Mulloy 1958) and occurred as a thick, charcoal laden zone of burned rocks, juniper bark, and artifacts. Deep firepits filled with rock fragments or river cobbles were associated with this level. The inter mediate occupation, in a six-inch thick stratum of reddish limestone rubble and sand, has not been identified but it may be Late Middle Prehistoric (Mulloy 1958). The Agate Basin zone was on, and slightly below, the surface of a stratum of fine, homogenous, light brown sand. The sand overlay reddish limestone rub ble and sand of undetermined depth. The rubble deposit sloped steeply downward 7 This content downloaded from 207.46.13.85 on Sat, 28 May 2016 06:17:49 UTC All use subject to http://about.jstor.org/terms from the rear of the shelter. The sur face of the sand was nearly horizontal; thus, it pinched out near the rear of the cave. Twelve small firepits were found in the Agate Basin level. These varied from oval to circular in outline and had straight or slightly inward-sloping walls and level or slightly concave bottoms. Maximum diameters ranged from 0. 8 to 2. 3 foot with the average being about 1.5 foot. Depths ranged between 0.25 foot and 0. 7 foot and averaged 0. 45 foot. Fill consisted of stained sand and pieces of charcoal. The charcoal varied from scarce to abundant and particle sizes ranged from small bits to moderately large pieces. There was no apparent pattern in the placement of the firepits, but they were concentrated in the area beneath, and a short distance inside, the outer edge of the cave roof. Charcoal from two of the firepits was sent to the Smithsonian Institution Divi sion of Radiation and Organisms for ra diocarbon dating. The results fall very nicely within the suggested time range for the Agate Basin complex of from 8000 B. C. to 5000 B. C. (Roberts 1961: 132). Sample No. SI-98 was dated at 8690 + 100 years B. P. (6740 B. C. ), and Sample No. SI-101 gave a date of 8600 + 100 years B. P. (6650 B. C. ).

Nearshore Sands Off Southeastern Virginia: ABSTRACT

In 1961 and 1962, SCUBA divers examined nearshore sands off southeastern Virginia and collected surface samples and 52 short cores, 2 inches in diameter and up to 4 feet long. The samples were analyzed by standard laboratory procedures. Two relict populations were recognized: (1) a coarse-grained (median about 1.5 phi) brown sand; and (2) a fine-grained (median about 3.3 phi) gray sand. The brown sand exists principally in linear ridges, whereas the gray sand occupies lower areas between ridges. The two sands are found interbedded in layers up to 10 cm. thick in cores taken from the landward side of a nearshore submarine ridge off False Cape. Though both sand populations have been derived from reworking of older Pleistocene deposits, both contain abundant Recent shell debris. Ripples covered the bottom continuously from just outside the surf zone outward to the outer limit of effective wave action, which varied from a line about 3 miles offshore in water 28 feet deep after a period of calm weather, to a line more than 9 miles offshore in water 71 feet deep after a moderate storm. Long axes of all active ripples measured were parallel to shore in spite of a 90-degree divergence (NE to SE) in direction of wave approach. Farther offshore ripples occur only on submarine ridges. Differential impregnation of longitudinally cut core surfaces with epoxy cement revealed numerous primary sedimentary structures, chiefly cross-laminae of both normal and oversteepened dip and burrow structures. Four stations were occupied in the summers before and after the intense storm of March, 1962. Cores collected here illustrate the principle of shelf sedimentation generally attributed to Barrell (1917) but first propounded by H. C. Sorby (1857) that a slow average rate of vertical accretion is combined with evidence of rapid deposition of individual layers. End_of_Article - Last_Page 357------------

Über eine interessante Froststruktur im episodisch-solifluidal bewegten Boden während der Würmeiszeit

Abstract. A frost-kettle is described as situated in the eastern part of the town of Bielefeld and reaching about 3 m into green and red marl, which had been moved episodically during the Würm glaciation. The frost-kettle was filled with yellow sand and glacial rubble as well as 4 layers of brown sand with small particles of clay (2.5 cm thick), inserted at regular intervals into the yellow sand. The brown layers showed a frost-upheaval of 5.5 cm in the centre due to hydration in a cold stadium of the last glaciation. While the yellow sand was washed into the cleft during the summer thawing periods, the clay particles of the brown layers consisting of weathered marl were blown into it after the soil had been dried. As loess-loam lies above a stone-layer showing no frost-dynamic modifications, the frost-kettle must have been formed during the second phase of the Würm glaciation, i. e. the high-glacial period.

Successful Pilot Predicts Bright Future for Loco Hills Water Flood, New Mexico

Abstract The Grayburg-San Andres reservoirs of the Artesia- Vacuum trend, Eddy County, N. M., have produced more than 2 million bbl of primary oil. The rock characteristics and production performance of these reservoirs indicate that many of them should yield substantial volumes of secondary oil. This paper describes the performance of one of the most successful waterflood pilot operations in the Artesia-Vacuum trend. The Newmont Oil Co. pilot in the Loco Hills field consisted of six injection wells in a modified five-spot pattern. Existing producing wells were converted to injection and a local water supply was used until response justified construction of a 26-mile pipeline to deliver sufficient water volumes for full development. Production rates in individual pilot wells increased from 400 to more than 18,000 bbl/month by June, 1960. Injectivity profiles indicate that this field must be flooded at high injection rates and pressures to effectively sweep all of the productive sand and that the reservoir appears to be quite sensitive to variations in injection rates. Additional development of Newmont leases surrounding the pilot area has continued, and the project had 15 injection wells and 47 producing wells on Feb. 1, 1962. These properties, which were producing 444 B/D in Aug., 1958, averaged 2,618 B/D in Jan., 1962. Unit volume recoveries in the pilot flood indicate that the Loco Hills field should be one of the more important secondary recovery projects in New Mexico. Introduction The Loco Hills field is located in the southwestern part of the Artesia-Vacuum trend of Eddy County, N. M., in a minor syncline on the flank of the Grayburg-Jackson monocline. Location of the field is presented in Fig. 1. The reservoir is a stratigraphic trap limited on three sides by permeability pinch-outs and on the east by a static water table. The principle producing formation his Zone 4 of the Grayburg formation of Permian age, locally known as the Loco Hills sand. This zone occurs at an average depth of 2,750 ft. It has good continuity throughout the area examined and, from the data at hand, appears to have uniform characteristics from well to well. The "typical" Loco Hills section consists of 10 to 30 ft of tight gray sand or sandy gray lime, underlain by 20 to 50 ft of soft brown sugar sand. Only the brown sand has a native permeability high enough to permit natural flow. History of Development The discovery well in the Loco Hills field Yates, et al, Federal No. 1 is located in the NW/4 of SW/4 Section 6, T-17-S, R-30-E. This well was completed in Jan., 1939, for a potential of 506 BOPD after being shot with 140 qt of nitroglycerine. Development on random spacing followed rapidly until the field ultimately contained 264 wells over a surface area of approximately 8,500 acres. JPT P. 1223^

North-South-Trending Submarine Ridge Composed of Coarse Sand Off False Cape, Virginia: ABSTRACT

A narrow north-south-trending submarine ridge composed of coarse brown sand lies seaward of False Cape, Virginia. The ridge joins the present coast at the Virginia-North Carolina boundary (36° 33^prime N.) and extends northward approximately 8 miles to a point southeast of Little Island Coast Guard Station (36° 40^prime N.). The ridge is well defined by the 30-foot depth contour. Depths of 16-20 feet are common along the crest of the ridge; the water deepens to 30 feet or more on both its landward and seaward sides. The bottom sediment consists of fine gray sand in the deeper water landward and seaward of the ridge and also north of it. The surface of the coarse-grained sand on the ridge consists of symmetrical ripples with wave length of 50 cm. and height of 10 cm.; these ripples were active on a day when the height of the swell was 2-3 feet. The fine-grained sand landward of the ridge showed symmetrical ripples of 10 cm. wave length and 2-4 cm. height under the same swell conditions where the depth was less than 25-30 feet. In water of greater depth, no ripples were present and the bottom consisted of mounds and pits and other organic structures. The ridge is only one of a series of north-south-trending linear sand bodies that occur both landward and seaward of the modern shoreline. These ridges are tentatively interpreted as ancient coastal dune-beach complex which formed at various Pleistocene stands of the sea but have been truncated by the present shoreline, whose trend is approximately N. 30° W. from Cape Hatteras, North Carolina, to Cape Henry, Virginia. The origin of this change in trend of shoreline orientation is not known at the present time. End_of_Article - Last_Page 278------------

Weathering of a Quartz Diorite at Marble Point, McMurdo Sound, Antarctica

Methods established by Goldich (1938) in his classic study of rock weathering have been applied with some modifications to analysis of a weathered rock series collected in the Antarctic. Exposures of a finegrained quartz diorite exposed at Marble Point, McMurdo Sound, were selected for study because they appeared to have undergone extensive chemical weathering beyond the effects to be expected in a region of such extreme cold and aridity. The light-gray, well-knit rock is altered in its most weathered form to a rich brown sand with angular particles as small as 0.003 mm. Complete chemical analyses of the rock in six of its weathering stages were obtained, and the trends established by these data were correlated with the mineralogie changes. Contrary to the impressions gained in the field, the bulk chemical and mineralogie composition of this rock has remained constant throughout the observed weathering sequence. There is no substantial change in alumina, combined silica, soda, lime, or potash which are normally sensitive indicators of chemical action. No clay forms in the weathering process. The only appreciable change involving an original constituent of the rock is the progressive oxidation of ferrous iron in pyrrhotite and biotite and the resulting formation of limonite which is responsible for the pronounced difference in color of the physically weathered debris. Seventy per cent of the original ferrous oxide is lost, and 45 per cent of total iron oxide is leached from the rock. Small amounts of halite deposited by evaporation of sea spray and native sulfur, presumably derived from volcanic fumes of Mt. Erebus, are found in the more-weathered materials at Marble Point. Their abundance relates to weathering only in that the disintegrated rock is physically more favorable to accumulation of these exotic substances. Oxidation of the native sulfur has contributed acid to the surface debris and thereby promoted rapid decomposition of pyrrhotite in the fresh rock and the pronounced iron staining in the weathered outcrops. The maximum volumetric changes caused by oxidation and hydration of the original minerals is negligible, and it is concluded that the mechanism primarily responsible for the observed breakdown of the rock is the combined action of frost-wedging and the crystallization of salt in pores and crevices in the weathering rock. Continuous records of the ambient air temperatures taken at Marble Point during the summers of 1957-58 and 1958-59 suggest that about thirty freeze-thaw cycles affect the site each year. However, on unclouded days rock-surface temperatures are considerably higher than air temperatures, and the number of freeze-thaw cycles in the rocks probably does not correspond to that indicated by air-temperature measurements. This study began as an investigation of what appeared to be a case of strong chemical weathering in the Antarctic and has ended in providing quantitative proof of the predominance of physical processes, a predominance commonly accepted on qualitative grounds.

Submarine geology of San Pedro Shelf [California

The submarine area off San Pedro, California, consists of a shallow shelf which extends seaward 3 to 12 miles and is bordered by a steep escarpment leading down into the deep San Pedro Basin. The shelf and escarpment are cut by a prominent sea valley and two smaller valley-like features. Shale, limestone, and sandstone of middle Miocene age are exposed on the central shelf. Late Miocene mudstone crops out on the shallow inner shelf, and early Pliocene siltstone occurs on the steep escarpment at relatively great depths. The ages and distribution of the rocks indicate that the lithology and structure of nearby Palos Verdes Hills extends southeastward onto the submarine shelf and escarpment. Unconsolidated sediments on the shelf are subdivided into six types according to their texture and color. Finest sediment is found behind the breakwater inclosing the shoreward part of the area. Coarsest sediment is a yellowish brown sand on the central shelf and is believed to be residual from Pleistocene conditions. Sediment sorting within the area correlates well with known currents.

Brown Men and Red Sand: Journeyings in Wild Australia

Brown Men and Red Sand: Journeyings in Wild Australia