Marine Landforms Research Articles

Middle-Late Pleistocene polycyclic evolution of a stable coastal area (southern Apulia, Italy)

The Otranto–Leuca coastal tract is marked by the presence of numerous sea caves placed close to present sea level. They are located generally at the back of a shore platform covered by a sequence of breccia deposits, marine sediments and speleothems. At Grotta di Masseria dell'Orte, marine cemented sands rest on a narrow shore platform at about 6.2 m above mean sea level and are covered by speleothems older than 185 ka. At Grotta del Diavolo, which is mostly filled by breccia deposits, three beach levels have been detected at about 3.0, 3.5 and 5.9 m above msl. They are either covered by or overlie speleothems that yield an U/Th age of 340, 78 ka and between 170.3 and 146.5, respectively. Geomorphological evidence and radiometric ages indicate that the area after a period of uplift has been tectonically stable since the last part of the Middle Pleistocene so that marine landforms close to the present shoreline underwent a polycyclic evolution. The sedimentary fills of sea caves formed during Middle-Late Pleistocene glacial stages, when arid or semiarid conditions promoted the removal of regolith and the development of thick breccia deposits. During Marine Isotope Stages (MIS) 9.3, 5.5 and 5.1, cave sediments were partially eroded whereas beach layers and related speleothems developed. These are, in fact, the only marine isotope stages marked by a sea level position which in this Mediterranean region was either close to, or slightly higher than, the present one.

Late Pleistocene and Holocene depositional environments and paleoceanography of the Barents Sea: evidence from seismic and biostratigraphic data

On the basis of seismic, lithological and biostratigraphic data from the Barents Sea shelf, a spatial correlation of the glacial, glaciomarine and marine landforms and deposits is established. The stratigraphic boundaries are established on the basis of biostratigraphic and lithostratigraphic data and correspond to the boundaries of seismostratigraphic units. Thus it is possible to trace reflectors as time-lines. During the Late Pleistocene and Holocene, the Barents Sea existed as a marine basin in which depositional environments changed from marine (Mikulino (Eem) interglacial) to glaciomarine (Würm glaciation), and back to marine (Holocene). Variations in intensification of the Atlantic current seem to be the most significant paleoenvironmental factor in the Pleistocene and Holocene history of the Barents Sea. The important event during the Holocene history of the sea is the period of ‘hydrobiological or marine optimum’ characterized by high productivity and increase in surface and bottom water temperatures. This interval corresponds to the end of the Atlantic stage and the beginning of the Subboreal stage, whose range, in the Barents Sea, is estimated as 5.7−3.7 ka BP. There is good accordance with data obtained from other Arctic Eurasian Seas.

Cold Climate Landforms

Permafrost landforms and regional reconstructions periglacial landforms glacial and fluviglacial landforms marine and lacustrine landforms polygenetic landforms cold climate slopes rock glaciers.

Sea-Level Research: A Manual for the Collection and Evaluation of Data

IGCP Projects 61 and 200. Sea-level changes in the Holecene. Sea-Level indicators: Elevation and age relationships: raised marine deposits and landforms in glaciated areas. Sea-level markers in coastal barrier sands: examples form the North Sea coast. Marine molluscs as indicators of former sea-level stands. Beachrock as sea-level indicator. Ooids as sea-level indicator. Corals and reefs as indicators of paleo-sea levels, with special reference to the Great Barrier Reef. Coralline algae as indicators of sea-level. Vermetid gastropods as sea-level indicators. The diagenetic products of marine carbonates as sea-level indicators. Marine notches. Submerged forests as sea-level indicators. Analysis of botanical macro-remains. Foraminafera as sea-level indicators. Diatoms as indicators of sea-level change. Shell middens as a source for additional information on Holocene shoreline and sea-level reconstruction: examples from the coast of Brazil. Age: Radiocarbon dating. Dendrochronological dating. Altitude: Determination of altitude. Compaction and consolidation.

Potentially acid sulfate soils in relation to landforms and geology

On the basis of analytical results from about 8000 augerings, the wetlands of Jutland, Denmark, were subdivided into four map units: Without potential acid sulfate soils; and with up to 20, 20 to 50 and more than 50% of the augering containing potential acidity. This map was combined with existing geomorphological and geological maps in order to estimate the frequency of potentially acid sulfate soils in wetlands in different landforms. Of the total wetland area (one fifth of Jutland), about a quarter is potentially acid sulfate. The proportion ranges from half in the coastal march area to about a fifth in the other marine landforms. In the non-marine landforms, more than a third of the wetlands in Saale glaciation landscape and in the outwash plains are potentially acid sulfate; in the wetlands of the other non-marine landforms the proportion is less than a fifth. This difference is explained by geological substratum. In northern Jutland this is pure Cretaceous limestone, while in the rest of Jutland Tertiary pyritic mica-rich sand and clay dominate. The development of potential acidity in the wetlands is probably due to a migration of iron and sulfur from these deposits, or from tills with Tertiary fragments, to the wetlands where the iron and sulfur have precipitated as pyrite in the organic-rich sediments.

Quaternary rivers on the New Jersey shelf: Relation of seafloor to buried valleys

The Quaternary evolution of the stream net on the New Jersey shelf has been interpreted on the basis of bathymetric maps and also by means of seismic profiling, with somewhat different results. Maps show the most recent positions of seafloor shelf valleys, but these valleys may have been created by retreating estuary mouths rather than by subaerial stream erosion. Seismic profiles reveal buried valleys of subaerial fluvial origin, which may follow courses that diverge markedly from the trends of associated seafloor valleys. Shelf valleys must be understood in the context of erosional shoreface retreat, a process that largely remade the shelf surface during successive Quaternary transgressions. Most shelf landforms are marine and post-transgressional in origin, having been formed at the foot of the shoreface. Only very large and deeply incised subaerial landforms survive the shoreface-retreat process. The marine landforms that tend to replace or bury subaerial river valleys include shelf valleys created by estuary-mouth scour, shoal-retreat massifs, and shelf deltas. Three distinct shelf valley sets, including both seafloor and buried valleys, are attributable to the ancestral Delaware, Great Egg, and Hudson Rivers, respectively. Individual valleys within valley sets may follow markedly divergent paths. In the case of the Hudson, the estuary retreated up a deeply incised river valley and was confined by it; the shelf valley is a river valley only partially filled by estuarine deposits. In the case of the other two rivers, the estuary mouths became largely decoupled from the underlying river valleys during the transgression, and their retreat paths do not everywhere overlie the buried channels. In each valley set, divergent buried valleys apparently belong to periods of subaerial exposure of the shelf that occurred earlier in Holocene time.

Atlantic Coastal Plain Terraces and Terrace Formations: ABSTRACT

The relation between coastal-plain terraces and their underlying has long been obscure. Atlantic coastal-plain terraces are underlain by formations in the sense proposed by Stephenson (1928). They consist of continental and marine contemporaneous cyclic sequences. The continental sequence consists of stream, fresh-water, marsh, lacustrine, estuarine, and deltaic sedimentary facies. The marine cycle consists of littoral, sublittoral, bar, barrier island-lagoon, and barrier-island tidal-marsh sedimentary facies. The two sequences are gradational within estuarine facies and disconformable along former strandlines. The cyclic overlie an unconformity that has been cut into older stratigraphic units. Landward the unconformity surface consists of stream valleys and divides over which the continental sequence was deposited during a rise in sea-level. Seaward the unconformity has been modified by marine scour. The marine sedimentary sequence occurs on this scoured surface. Initial marine erosion proceeds landward during a rise in sea-level until estuaries are filled and sediments supplied to the ocean balance sediments being eroded. From this stage onward, during slow transgression through subsequent regression, coastal-plain accretion takes place seaward with construction of one or more barrier-island and tidal-marsh stages and seaward growth of deltas. The terminal surface of the cyclic formation is the terrace which contains both continental and marine land forms representing the last processes operative in the area during regression. Thus geomorphology and pedology reflect the terminal nature of the underlying litho-, bio-, and environmental facies. The underlying stratigraphic facies illustrate the cyclic sequence of environmental stages necessary to develop the terminal land form. End_of_Article - Last_Page 459------------

Ground-Geology and Natural Disasters due to Soft Ground Conditions in the Shizuoka-Shimizu Region, Central Japan

The occurrence of not only such natural disasters as ground subsidence due to the taking up groundwater, earthquake damage, flood losses, etc. but also such public nuisances as river pollution, air pollution, etc. have recently increased in the urban areas of Japan which are situated on recent alluvial lowlands along the coastal region, and accompany the rapid development of these regions, i. e. the rapid growth of industry and the rapid increase of population in these regions. Among the disasters, almost all of the natural disasters occurred in soft ground areas in connection with poor land and water utilization. Therefore, to examine and forecast the danger from disasters due to soft ground conditions is most important to allow reasonable plans for the regional development and the prevention of disasters to be made.The Shizuoka-Shimizu region, situated on the Pacific coast of Central Japan, is expected to be developed as a metropolitan area by the combination of two cities, Shizuoka and Shimizu (Fig. 1). The distribution and physical properties of soft ground, and problems of prevention of natural disasters caused by soft ground conditions, particularly earthquake damage, are described and discussed in this paper.(1) The recent alluvial lowlands in the region investigated, the Shizuoka-Shimizu Lowland, are limited by the Tertiary mountains to the north and Suruga Bay to the south (Fig. 2). The River Abe flowing down from the southern part of the Southern Japan Alps and having a great landslide area on its upper reaches, Ohya-kuzure, passes through in the western part of this region to enter the sea, and the eastern part of this region lies in the catchment area of the River Tomoe, which rises in the Tertiary mountains (Table 2). The Udo-san Hilllands composed mainly of Pleistocene gravel layers and having a plateau on the top, called Nihondaira, is located in the middle part of this region.Fig. 2 is a landform classification map compiled by aerial photographic interpretation. Micro-landform units shown in this map are classified systematically by origin and composition to inferred engineering soils, based on the methods and techniques of micro-geomorphological analysis for engineering soil surveys from aerial photographs (Kadomura 1965, 1966). From this map, the Shizuoka-Shimizu Lowland is divided into several “landform areas” as shown in Fig. 3 and Table 1, depending upon the distribution pattern of micro-landform units, the geomorphological agents, their topographic locations and other criteria.The “landform areas” consisting of gravelly layers are divided into two categories fluvial landforms such as alluvial fans and gravelly valley bottom lowlands, and marine landforms such as coastal shingle bars and sand banks. The areas of poorly-drained deltaic lowlands, which originated from former lagoons blocked by shingle bars and sand banks, are distributed along the both sides of the R. Abe Fan and in the downstream area of the R. Tomoe. These deltaic lowlands are formed of thick muddy deposits mentioned later. During the formation of these poorly-drained muddy lowlands as well as the formation of soft ground, coastal shingle bars and sand banks, which formed before the formation of the muddy lowlands, played a important role.(2) The ground in this region investigated and the surrounding mountain lands is divided into unit layers as in the other coastal lowlands of Japan shown in Table 3, for comparison of their relative foundation bearing strengths. Among these unit layers, the Upper Muddy Layer (Um), the Lower Muddy Layer (Lm), and a part of Upper Sand-and-Gravel Layer (Usg) composed mainly of sandy soils (Us), which are distributed along the margin of the Shirnizu Sand Bank and in abandoned low water channels, should be noted as soft ground layers.