Calcareous Silt Research Articles

Stratigraphy and Structure of Clinton Section in Wayne County, Ohio: ABSTRACT

The Clinton section in Wayne County represents a clastic wedge of the Lower Silurian Albian Group. It was deposited on the distal flank of the Appalachian basin as a result of the Taconic orogeny. The section extends vertically from the Queenston unconformity to the base of the Packer shell (Brassfield Limestone). It is primarily composed of sandstone, shale, limestone, and dolostone. Within this stratigraphic section, the sandstone facies is an important hydrocarbon reservoir rock. The sandstone facies pinches out laterally along a north-south depositional limit that is roughly located along the western boundary of Wayne County. The study relied primarily on geophysical log data. However, drill cuttings were used to correlate lithologies to specific curve assemblages on the geophysical logs. This helped define lithologies to logs in areas where drill cuttings were lacking. Eight cross sections--four north-south and four east-west--show the complexity of the intertonguing clastic and carbonate deposits resulting from the progradation and shifting of deltaic and nearshore marine environments. The cross sections also show that the driller's terms of stray, red (1st), and white (2nd) Clinton sandstone are arbitrary units and are not temporally equivalent or correlative from well to well over great distances. Stratigraphic interpretations indicate that the deposition of the Clinton section began with a marine transgression from the northwest across a subaerially exposed coastal plain that was deposited as the distal end of the Ordovician Queenston delta. This transgression reworked the upper Queenston sediments and redeposited them as calcareous silts and sands. Renewed uplift of the Taconic highlands caused a clastic influx into the areas and a relative regression of the sea. These sediments were deposited in prodeltaic and lower delta-plain environments. Some of the sediments were reworked offshore by ocean currents and wave action and redeposited as offshore bars. As the influx of Taconic sediment ended, muds were deposited, which were eventually transgressed by a carbonate-rich sea. A imestone unit, the Packer Shell, was then deposited ending the Alexandrian Epoch. The structural setting is one of homoclinal dip to the southeast, with localized basement-controlled, minor folds normal to the basinal axis. Small-scale faulting can also be seen on structure maps of the base of the Packer Shell and the top of the Queenston. Local structural highs and faults affect oil and gas production in this mainly stratigraphic trap. Local structure commonly segregates the oil and gas in the same reservoir body. End_of_Article - Last_Page 1930------------

Seasonal Zn, Cu, Mn, and Fe Levels of Western Wheatgrass and Green Needlegrass as Affected by N Fertilization1

AbstractNitrogen fertilization has been used to increase forage production of range grasses in the northern Great Plains; however, little information is available as to how N fertilization affects minor element composition of range forage. Our objectives were to determine the effects of N fertilization on Zn, Cu, Fe, and Mn concentrations in vegetative and floral tillers of western wheatgrass (Agropyron smithii Rydh.) and green needlegrass (Stipa viridula Trin.) throughout the growing season. Nitrogen fertilizer (0,40,80,160,320, and 640 kg N/ha) was applied in a completely randomized design to each grass species growing on a calcareous silt loam (Typic Haploborolls). Plants were collected on 10 and 11 sampling dates in 1973 and 1974, respectively. Nitrogen fertilization significantly increased the level of Zn, Cu, and Mn in green needlegrass and Zn and Mn in western wheatgrass forage. Absolute changes in mineral composition caused by N fertilization were very small and of little practical significance. Forage Zn and Cu levels declined throughout the growing season and were generally below recommended allowances (less than 20 to 30 πg/g Zn and 4 πg/g Cu) for proper cattle nutrition by mid‐June. Therefore, supplemental Zn and Cu may be required in diets of cattle being fed or grazing western wheatgrass or green needlegrass grown in the northern Great Plains after mid‐June. Forage Fe and Mn levels decreased as the growing season progressed until maximum forage yield was reached in June. Iron then started accumulating in the forage while Mn remained relatively constant during the remainder of the growing season. Iron (>80 πg/g) and Mn (>35 πg/g) were well above the recommended minimum levels for proper cattle nutrition. Floral tillers of both grasses had lower concentrations of Zn, Fe, Mn, and Cu than did vegetative tillers. In general, the earlier the harvest, the better the forage quality of western wheatgrass and green needlegrass will be with respect to Zn and Cu nutrition of cattle. Maintaining the grasses in the vegetative rather than floral growth stage would also improve forage quality

Upper Cambrian Intrashelf Basin, Nolichucky Formation, Southwest Virginia Appalachians

An intrashelf basin located on the Upper Cambrian carbonate-rimmed shelf (miogeocline) of the Appalachian orogene, appears to have controlled facies distribution during deposition of the Nolichucky Formation (0 to 985 ft; 0 to 300 m thick). The intrashelf basin was bordered along strike and toward the regional shelf edge by a rim of peritidal carbonates and by nearshore clastics toward the craton. The peritidal carbonates passed into the intrashelf basin by way of a gently sloping carbonate ramp. Peritidal facies are cyclic, upward-shallowing stromatolitic carbonates (Elbrook and/or Honaker Dolomite) that grade basinward into cross-bedded ooid and oncolitic intraclast grainstones. These pass downslope into subwave-base, deeper ramp, ribbon carbonates and thin limestone conglomerate (Maryville, Nolichucky lower limestone, and Maynardville limestone). Ribbon limestones are layers and lenses of trilobite packstone, parallel and wave-ripple-laminated quartzose calcisiltite, and lime mudstone arranged in storm-generated fining-upward sequences (0.39 to 2 in.; 1 to 5 cm thick) that may be burrowed. Intrashelf basin facies (Nolichucky lower and upper shale) are storm-generated sequences of green calcareous shale with open-marine biota; parallel with hummocky laminated calcareous silt tone; and intraformational flat-pebble conglomerate, and skeletal or ooid limestone with trace fossils, glauconite zones, and hardgrounds. A 49 ft (15 m) thick tongue of bioherm-bearing cyclic carbonates within the shale package (Nolichucky middle limestone) developed during a period of shoaling of the intrashelf basin. Development of the Late Cambrian carbonate-rimmed shelf and its intrashelf ramp and basin may have been influenced by high carbonate production along the regional shelf edge, by tectonic subsidence associated with a major shelf depocenter, and by influx of terrigenous sediments which suppressed carbonate deposition in the basin. Understanding the Nolichucky facies within a ramp to intrashelf basin model provides a framework for understanding similar continental-shelf facies which are widely distributed in the lower Paleozoic and in the subsurface of the Mesozoic. Recognition of basins located on pericratonic shelves is important because such basins influence the distribution of potential petroleum source beds and reservoir facies whose trends may be unrelated to regional shelf-edge tr nds.

Alakir çay group, antalya complex, SW Turkey: A deformed mesozoic carbonate margin

The Alakir çay Group comprises complexly deformed Mesozoic sedimentary rocks originally deposited along a passive carbonate margin. The sediments now form a tectonically imbricated stack of thrust sheets (Kumluca Zone) emplaced westwards over a relatively autochthonous carbonate platform (Bey Dağlari Zone). The Kumluca Zone is bounded tectonically to the east by mafic and ultramafic rocks with related sediments (Gödene Zone), representing oceanic crust produced during early stages of continental separation and originally forming the more distal part of the margin. Detailed mapping and structural analysis allow the thrust sheets to be pulled back to reconstruct a stretch of the carbonate margin about 10 km wide by 25 km long. Within the thrust sheets, fragmentary basal sequences of quartzose sandstones (Hatip Formation), derived from the north, were laid down during late Triassic continental rifting. Subsequent late Triassic Halobia- and radiolarian-bearing calcilutites (Bozyer Foramtion) are comparable with ‘peri-platform’ deep-water oozes found, for example, in the Bahamas. An end-Triassic hiatus involved substantial down-margin sediment redeposition. Jurassic to early Cretaceous sediments include both non-calcareous and calcareous silts laid down together with radiolarites in deep water below the carbonate compensation depth (Karabük Formation). An upward transition to Cretaceous planktonic foraminiferal chalks is seen in some more proximal sequences. Tectonic disruption of the margin began in latest Cretaceous time and ended with westward thrusting over the carbonate platform in the Miocene. Small-scale facies variation of the margin is illustrated by unstretching the thrust sheets and correlation of 33 measured logs. Particularly, the sediments become more distal across the margin away from the carbonate platform. Along-margin variation is especially evident in the thickness and composition of redeposited carbonates in the late Triassic hemipelagic rocks. Comparison with other carbonate margin sequences in the Antalya Complex and elsewher implies that the Alakir çay sediments represent deep-water outer-margin facies which lapped over adjacent oceanic crust: more proximal redeposited carbonates are not seen, perhaps due to overthrusting.

The taxonomy of Bryum oblongum and B. blindii

Plants agreeing with the type specimen of Bryum oblongum Lindb. were found in northern British Columbia, the Yukon Territory, and Alaska. Bryum oblongum is otherwise known from central Europe, Fennoscandia, and northern Asia. Some authors have considered B. oblongum to be a variety or subspecies of B. blindii B.S.G., with which it shares a number of structural features. Shared and presumed apomorphous (derived) character-states indicate that B. oblongum and B. blindii are closely related, but quantitative evidence shows that the two can be distinguished by at least four structural characters. Propagula were found on about 20% of the total specimens of B. blindii examined, but no propagula were observed on B. oblongum. Ecological data from collection information indicate that B. blindii occurs primarily on calcareous silts and clays, while B. oblongum is more frequent on mildly acidic to neutral substrates. Bryum oblongum is considered a distinct species, and both taxa are described and illustrated.

Nitrogen Fertilization Effects on Seasonal Ca, Mg, P, and K Levels of Western Wheatgrass and Green Needlegrass1

AbstractNitrogen fertilization has been found to increase forage production of range grasses in the northern Great Plains; however, little information is available as to how N fertilization may affect the mineral composition of the forage. Our objective was to determine the effects of N fertilization on the levels of P, K, Ca, and Mg, and the grass tetany proneness of the vegetative and floral tillers of western wheatgrass (Agropyron smithii) and green needlegrass (Stipa viridula) throughout the growing season. Nitrogen fertilizer (0, 40, 80, 160, 320, and 640 kg N/ha) was applied in a completely randomized design to each grass species in a calcareous silt loam (Typic Haploboroll). Plant samples were collected on 10 and 11 sampling dates in 1973 and 1974, respectively. Nitrogen fertilization generally increased Ca, Mg, K, and ash alkalinity and generally had little effect on the P levels of the forage; however, the absolute changes caused by N fertilization were very small and of little practical significance. Except for K and P, the level of each nutrient generally increased significantly in each grass as the growing season progressed from April to October. Season or growth stage had more effect than did N fertilization on forage nutrient content. Floral tillers had lower levels of each nutrient than did the vegetative tillers. The Mg and P contents of both the floral and vegetative tillers of both grasses were often < 0.2%. Therefore, supplementation of Mg and P to grazing livestock may be required. The potential for grass tetany, according to the K/(Ca + Mg) ratio of the forage and blood serum Mg estimates, was highest during April and May for both grasses. Western wheatgrass tended to have a greater potential for causing tetany than green needlegrass early in the growing season. Time of harvest and percentage of vegetative and floral tillers can greatly affect the concentration of K, P, Mg, and Ca in the forage. In general, the earlier the harvest, the higher the nutritional value of the forage.

Effects of cultivation on the distribution of nutrients in the soil and the uptake of nitrogen and phosphorus by spring barley and winter wheat on three soil types

The effects of cultivation, ploughing (20–25 cm), tine cultivation (7.5–10 or 15–20 cm) and direct drilling on the distribution of extractable soil phosphate and potassium were compared on a sandy loam, a calcareous silt loam overlying chalk and a calcareous clay. Effects on the uptake of nitrogen and phosphate by spring barley and winter wheat crops were also investigated. Direct drilling and the two depths of tine cultivation gave closely similar results and there was an increased concentration of extractable P and K close to the soil surface compared with the more uniform distribution through the tilled layer caused by the inversion of the soil by ploughing. In general, during the season phosphate concentration in the shoot dry matter and phosphate content per unit area in the crops were not affected by the differences in nutrient distribution. Thus no effects were detected in samples collected at the beginning of stem elongation. However, at anthesis in both crops phosphate content was greater after direct drilling than after ploughing. Ploughing resulted in significantly greater concentrations of nitrogen in the dry matter than did the other cultivation treatments. Averaging over both crops at the three sites, neither the yields of dry matter nor the total content of nitrogen differed significantly between cultivation treatments. The results give further confidence that simplified cultivation techniques including direct drilling are unlikely, at least in the short term, to affect adversely the uptake of nutrients by cereals. We emphasise the closely similar results in the distribution of nutrients in the soil when it was disturbed to varying depths but without inversion.

Trace Elements in Fly Ash and Their Release in Water and Treated Soils

AbstractFly ash from a coal‐fired power plant was separated into various‐sized fractions which were then chemically characterized. The fly ash contained higher concentrations of B, Co, Cr, Cd, Mo, Ni, Pb, As, and Se than normally found in soils. Except for Cd, Co, and Pb, trace elements were more concentrated in the < 53‐µm than in the > 250‐µm fraction. Solubility of trace elements in water increased greatly as the equilibrium pH was lowered.Three soils, an acid sand, a calcareous loamy sand, and a calcareous silt loam, were amended with five rates of fly ash up to 1.0% by weight and equilibrated at moisture contents of 1/3 bar or saturation for periods ranging up to 29 weeks. Solubility of trace elements in water and DTPA extracts were observed. Application of fly ash increased soil pH; the acid soil exhibited the greatest increase. Except for B, fly ash amendment up to 1.0% did not result in elevated concentration of either water‐soluble or DTPA‐extractable trace elements. Additions of fly ash to the acid soil decreased DTPA‐extractable Fe, Mn, Ni, Co, and Pb. The data demonstrated that the alkalinity of fly ash plays a significant role in regulating the availability of trace elements in the amended soils.

Mineralogy and grain size distribution of dust fallout in Kuwait

The mineralogy and grain size distribution of some dustfall samples collected during the summer of 1978 in the City of Kuwait were determined. It was found that dustfall sediments in Kuwait are composed mainly of calcareous silt. They are also characterised by the frequent occurrence of dolomite and gypsum. Based on their mineralogical composition, prevailing wind direction and comparison with Iraq dust storm sediments, it is suggested that the dust storm sediments of Kuwait are most probably derived from the dry flood plain deposits in South Iraq. The surface deposits of Northwestern Kuwait could contribute partly to these sediments.

The Petrology and Depositional Environments of the Middle Cambrian Wirrealpa and Aroona Creek Limestones (South Australia)

ABSTRACT A petrographic study of acetate peels made from approximately 500 carbonate rock samples from the early Middle Cambrian Wirrealpa and Aroona Creek Limestones led to the identification of nine major rock types. Carbonate grains include well-rounded ooids, oncolites, intraclasts, peloids and fossil fragments. Textures range from grainstones to mudstones. Nodular and semi-nodular layers, regularly interbedded with thin, wavy, calcareous silts, are common throughout. Two megafacies, composed of eight facies, were identified in most of the 22 measured sections. Interpreted depositional environments for these two megafacies arc--(1) an ooid bank area close to the oceanward margin of a shallow intracratonic platform, characterized by mobile ooid shoals intertonguing between areas of lesser t rbulence, and (2) a shallow, marine lagoon, behind the ooid shoals characterized mainly by less turbulent depositional conditions, calcareous silts and stromatolites. The detailed analysis of facies in one outcrop area provides a clear record of a marine transgression-regression cycle. Extrapolation to four other outcrop areas enables tentative paleogeographic reconstructions for the whole Arrowie Basin to be hypothesized. These suggest that the transgression came from and probably retreated to the northern areas of the basin.

A Reexamination of Globulinella (Musci; Pottiaceae)

A study of available specimens of Globulinella has resulted in a re- alignment of some species and a significant range extension. Globulinella globi- fera (Hampe) Steere is reported for the first time to the United States. Gyro- weisia benoistii Ther. is transferred to Globulinella and Gyroweisia obtusifolia Broth. is removed from synonymy. During the summer of 1973 a small pottiaceous moss was collected on a calcareous outcrop in the Chisos Mountains of Big Bend National Park, Brewster County, Texas. Several months later another specimen was collected on calcareous silt in the desert be- low the mountains. The specimens were identified as Globulinella globifera, resulting in a considerable range extension for the species. A similar extension, recently reported for G. peruviana (Sharp & Bowers, 1975), indicated the need for a critical reexamina- tion of the genus. The nomenclatural history of Globulinella began when Hampe (1870) described two species, Seligeria globifera and Trichostomum obtusifolium, from specimens col- lected by Strebel in Veracruz, Mexico. Several years later Miiller (1897) published the genus Globulina for a single species, G. boliviana. In a short note under the description, Miiller suggested Seligeria globifera Hampe might be placed in Globulina. In 1902 Brotherus made the combination, Globu- lina globifera (Hampe) C.Miill., attributing it to Miiller. At the same time he provided a new name for the later homonym Trichostomum obtusifolium Hampe, i.e., Gyroweisia obtusifolia Broth. Williams (1916) added a third species to Globulina, when he de- scribed G. peruviana for a small moss collected by Cook and Gilbert near Araranca, Peru. The first reexamination of the species of Globulina was undertaken by Hilpert (1933) in his study of Trichostomaceae. Hilpert recognized G. globifera and G. peruviana as

Pseudoditrichum mirabile gen. et sp. nov. (Musci: Pseudoditrichaceae fam. nov.), a unique moss from Great Bear Lake, Northwest Territories

The name Pseudoditrichum mirabile Steere et Iwatsuki is proposed for a minute moss with leafy stem 1-3 mm high and seta 6 mm long; it was collected on calcareous silt near the Sloan River, Great Bear Lake, Northwest Territories, only a few miles south of the Arctic Circle. The gametophytic characters agree well with those of the Ditrichaceae, a relatively primitive family, but the peristome is clearly double, with the inner and outer teeth opposite, which thereby indicates a much more advanced phylogenetic position, perhaps at the evolutionary level of the Funariaceae. As the combination of gametophytic and sporophytic characteristics exhibited by this moss does not occur in any existing family of mosses, it is therefore deemed necessary to create the new family Pseudoditrichaceae for the new genus and species described here.

Correlation and Paleogeography of Upper Part of Helderberg Group (Lower Devonian) of Central Appalachians

Physical stratigraphy and environmental relations in the upper part of the Helderberg Group have clarified the interpretation of biostratigraphic data in a previously enigmatic area of Appalachian Lower Devonian correlation. The Licking Creek Limestone, a marine carbonate shelf facies, is subdivided and its members (lower, Cherry Run Member; upper, Little Cove Member) are traced along the eastern outcrop belt from south-central Pennsylvania southward to central Virginia. Toward the northwest the Cherry Run increases in thickness and intertongues with the lower two thirds of the Shriver Chert, an offshore calcareous cherty silt and mud which occupies the depositional basin axis. The Little Cove rises stratigraphically toward the northwest and is traced into the upper part f the Shriver Chert. Lithologic and faunal differences of the equivalent units are caused by the differing, but time-equivalent, adjacent environmental settings (shallow shelf-basin axis). Lithostratigraphic evidence indicates that the upper contact of the Licking Creek-Shriver strata rises in the section in a northwesterly (basinward) direction and that the Licking Creek of the eastern outcrop belt intertongues with the lower two thirds of the Shriver in its type area. Biostratigraphic evidence indicates that faunal elements are added to the upper part of this interval as the contact rises. This evidence also suggests that the Licking Creek of the eastern outcrop belt and the lower two thirds of the Shriver are Helderbergian and the upper third of the Shriver is Deerparkian. Paleogeographic reconstruction of these correlations shows that (1) shoreline and facies boundaries are slightly oblique to the outcrop belt; (2) shallow carbonate facies tended to migrate westward (basinward) during this time, indicating a regressive trend just prior to Oriskany Sandstone deposition; and (3) the basin margin pre-Oriskany unconformity does not extend over large areas of the depositional basin itself. These conclusions are of potential significance for gas exploration in the upper Helderberg and overlying Oriskany Sandstone in relating subsurface stratigraphic facies and structure to the observed surface trends and correlations.

EFFECTS OF THE APPLICATION OF PHOSPHORUS, POTASSIUM, AND SULFUR TO ALFALFA GROWN ON A CALCAREOUS SILT LOAM

Studies were conducted to evaluate the interactions of P, K, and S applied to alfalfa grown on a calcareous silt loam. Phosphorus fertilization increased alfalfa yields. The application of K and S had no significant influence. In each of 2 years, the highest yields were obtained at the highest rate of P used. There was residual response to P applied in the previous cropping year. The P content of the alfalfa tissue was increased by P fertilization. The use of K and S had no influence on the tissue content of the respective nutrient. Soil P as measured by the bicarbonate extractant was related to previous P fertilization. This was not true for soil P extracted by the Bray procedure. The data in this study support the choice of the bicarbonate method for describing the P levels in calcareous soils.

Water‐soluble NO3‐Nitrogen, PO4‐Phosphorus, and Total Salt Balances on a Large Irrigation Tract

AbstractReturn flow from a 82,030‐ha (202,700‐acre) tract of calcareous silt loam soils irrigated with water diverted from the Snake River in southern Idaho increased the downstream total soluble salt and NO3‐N loads, but decreased the downstream PO4‐P load. Under the existing water management practice, 50% of the total input water returned to the Snake River as subsurface drainage. Net total soluble salt output was 2.4 metric tons/ha (1.0 English ton/acre) and, on the average, was considerably greater than necessary to maintain a salt balance. Net NO3‐N output was 33 kg/ha (30 lb/acre). Only about 30% as much PO4‐P left the tract via drainage water as entered the tract in irrigation water. As water passed through the soil, PO4‐P was removed by chemical reactions in the soil, thus decreasing the concentration in the subsurface drainage water and decreasing the downstream PO4‐P load. Applied P fertilizer was not leached into the drainage water.

Paleobiogeographic Zonation of Carboniferous in Northern Hemisphere: ABSTRACT

A Siberian biogeographic realm with the fauna and flora of a temperate-cool climate, and a Mediterranean realm with the fauna and floras of a tropical-subtropical climate existed in the Northern Hemisphere during all of the Carboniferous. There were no ammonites during the Tournaisian in the Siberian realm and the corals and brachiopods were less varied than in the Mediterranean one. Endemic brachiopod species are typical for the Siberian realm. The Siberian realm included the Verkhoyansk, Kolyma, Taimyr, Tunguska, and Chersk provinces. The Verkhoyansk and Kolyma provinces, with rich faunas, coincided with the shelf of the Kolyma massif and the Siberian platform that was covered by calcareous silt. Verkhoyansk and Kolyma were separated by the Chersk province which had a poor fauna typical of deep-water basins. The Tunguska province differed from the Taimyr province in variety of tournayellids and endothyrids present and in poverty of brachiopods, but is similar to Kuznetsk province in poverty of brachiopods. Only multifacial foraminifers remained among the Visean foraminifers of the Siberian realm. Ozaweinellidae became scarce during the time of Yasnaya'Polyana and Okhoye deposition. Endothyridae became scarce but archaediscids increased during the time of Serpukhov deposition. Corals were represented by impoverished complexes. The Siberian species constitute a large percentage of the brachiopods. During the Visean, the Siberian realm spread over the Omolon, Zaysan-Mongol, and Kazakhstan provinces. During the Serpukhov deposition, the Kolyma and Verkhoyansk provinces joined, and the Chersk province was eliminated as a result of structurally controlled facies changes. At the same time, the Tunguska and Kuznetsk provinces disappeared as a result of the continuing marine regression. In Late Carboniferous (Samodiye-early Bashkirian) time, the Archaediscidae continued to dominate in the seas of the Siberian realm; there were many local species and genera among the brachiopods. The fauna of that time was especially abundant in the Taimyr province, from where an arm of the sea extended south to the seaway in the Ob'-Zaysan geosyncline. East of the Kolyma massif, the Anyuysk province existed. Beginning with Kulom deposition (late Bashkirian), arenaceous foraminifers continued to develop in the seas of the Siberian realm; fusulinids, archaediscids, and other forms were completely absent. The brachiopods were represented mainly by endemic species and genera. The goniatites (including species common with those of Northern America and the Urals) were represented by Siberi n endemic species and genera. The most essential differences at that time took place between the faunas of Verkhoyansk-Kolyma province with its foraminifers, goniatites and brachiopods and Mongol-Okhotsk province where foraminifers and goniatites were absent. Not long before the end of the Carboniferous the goniatites had disappeared from the seas of the Siberian realm. At the same time, most brachiopods had become extinct. In the western part of the Arctic the Barents-Franklinian area had an impoverished fusulinid and goniatite fauna that differed from the faunas in the Mississippian basins of North America. End_of_Article - Last_Page 2513------------

Vermetid Reefs and Coastal Development in the Ten Thousand Islands, Southwest Florida

Sediments which underlie the Ten Thousand Islands have been deposited over the past 5000 years, during a more or less continuous marine transgression. Maximum sediment thickness is approximately 25 feet. Both the macrofauna and microfauna were used to help interpret the depositional environment for these sediments. The clean, slightly peaty basal sand was deposited in a lagoon with very restricted tidal circulation. When more marine waters entered the area about 3000 years ago, a chain of gastropod reefs appeared along the coastline. During the ensuing sea level rise of about six feet, the reefs have grown in size and number to form a reef barrier which has greatly influenced sedimentation throughout the Ten Thousand Islands. Sand from the adjacent shallow shelf has been transported into the reef area by the abnormally high tides and violent wave action accompanying hurricanes. A complex of bay bottom sands and silts, tidal pass sands, oyster bars, and thick mangrove peats has accumulated behind the reef barrier. Reefs were formed by the sessile gastropod Vermetus (Thylaeodus) nigricans Dall. The wave resistant reef core consists of fused vermetid tubes in a matrix of calcareous silt. Talus deposits typically underlie portions of the reef core. Formation of reef rock was confined to the intertidal zone, a vertical distance of less than four feet. Reef cores, as much as nine feet thick, were built up during the period of sea level rise. The vermetid reefs are compared with post-Wisconsin serpulid reefs from Laguna Madre, Texas, and with rudistid reefs from the Edwards Limestone of Texas.

Organic Carbon in Sediments of Japan Sea

ABSTRACT Analyses of 106 surface samples of the sediment on the floor of the Japan Sea were made for color, grain size, calcium carbonate, organic carbon, and mineralogy. The results showed that the sediments on the shelves and bank tops are largely coarse-grained green moderately calcareous sands having less than 1 percent organic carbon. Those on the basin slopes are fine-grained green (grading to olive brown below about 1800 m depth) slightly calcareous silts having 1 to 2 percent organic carbon. Below about 2000 m and covering the flat floor of the sea is yellow-brown clayey silt containing less than 1 percent calcium carbonate and less than 1 percent organic carbon. This deepest sediment approaches the character of red clay that occurs in the open ocean chiefly at depths of more than abou 3000 m. Its relatively shallow occurrence in the Japan Sea is attributed to the presence of an exceptionally high content of dissolved oxygen (about 5.3 ml/l) in the bottom waters of the sea. Their high oxygen content is due to sinking of surface waters at the north end of the sea during wintertime cooling.

Development of Basin-in-Basin Honeycomb of Florida Bay and Northeastern Cuban Lagoon: ABSTRACT

This triangular, 1,000-sq mi, bimodally windy, subtropical lagoon is a honeycomb of closely spaced, interconnecting, suboval, pan-shaped basins individually upward of 10 mi long and 12 ft deep. It lies north-south between multiple mangrove-swamp belts along the Everglades shoreline and the emergent barrier reef of the Florida Keys and east-west between Biscayne Bay and a zone of broad, marly, sandy and shelly shoals facing the Gulf of Mexico, north of Vaca Key. Basin walls of Holocene marl (mostly shelly calcareous silt grading above to mangrove peat) stabilized by alternations of mangrove-swamp bands and marine grasses form a honeycomb pattern throughout the lagoon. Walls rise to 2.5 ft and basin floors are as deep as 11-12 ft msl. Bottoms are muddy or floored by shell concentrate. Near the are bottom exposures of the underlying hard Pleistocene Miami Limestone. Basin areas and depths increase irregularly southward from tiny, oval, fresh-water, marsh ponds of the Everglades border, by multiple mergings and irregular loss of separating walls, to form large, nearly smooth-sided bays along the barrier reef with its keys cut by tidal inlets. The honeycomb pattern of the geographic map appears below water as a more intricate though fragmentary basin-in-basin structure. Alignments of basins, trending roughly north-south between nearly continuous mangrove belts which mark former rill-valleys of the Everglades marsh, cross northeast-southwest alignments separated by walls which have been reinforced by shoreline storm-debris ramparts. Aqueous erosion of a contemporaneously gradually thickening marl-and-peat formation is indicated by suboval basin form maintaining a rough width/depth relation in a windy region (Price, 1947), while sediment accumulating, in step with rising sea level, produced Scholl's (1964) dated regional stratigraphy of the last 5,000 to 4,000 years. The basin-in-basin honeycomb is the result of conflict between (a) aqueous erosion in saline basins, and (b) the strong sediment potential of tropical paralic vegetation, while (c) the erosion continued during the slow transgression of an 8-mi-wide fresh/salt contact zone like that of today which passed across a rock basin at first lightly carpeted with Everglades marsh. Thus, salt-denuded rill-valley lows developed oriented lakes, which were drowned to form tidal bays. Shoaling of ponds, with mangrove occupation, alternates today with flushing-out of wave-eroded marl. Total volumes of walls and water are now roughly equal. Patches of a similar basin honeycomb occur along 270 mi of the northeastern Cuban lagoon behind its emergent barrier reef. Pleistocene examples occur in Florida and Cuba. Drowned oriented Carolina bay lakes give a somewhat similar pattern along a Chesapeake Bay shore. No process of accumulation adequate by itself to form such honeycombs is known. The genetic process was the drowning and embayment of oriented lakes formed by similar action from drowned marsh rills. End_of_Article - Last_Page 2168------------

SCOUR RIPPLES IN THE LUDLOVIAN OF SOUTH RADNORSHIRE, WALES

SUMMARYCalcareous siltstone beds in the sub‐littoral marine sedimentary rocks of the highest Ludlovian (Upper Whitcliffian) in south Radnorshire display symmetrical ripples with wave lengths around 30 cm. These structures are interpreted as having been formed by the deposition of calcareous silt layers in conformity with bottom surfaces previously scoured into a pattern of symmetrical, gently‐rounded, crests and troughs; hence, they are termed scour ripples. There is some evidence of a longitudinal relationship between the scour ripples and the scouring and depositing currents involved in their formation.