Strandplain Research Articles

Classification of Australian Clastic Coastal Depositional Environments Based Upon a Quantitative Analysis of Wave, Tidal, and River Power

A statistical assessment of wave, tide, and river power was carried out using a database of 721 Australian clastic coastal depositional environments to test whether their geomorphology could be predicted from numerical values. The geomorphic classification of each environment (wave- and tide-dominated deltas, wave- and tide-dominated estuaries, lagoons, strand plains, and tidal flats) was established independently from remotely sensed imagery. To our knowledge, such a systematic numerical analysis has not been previously attempted for any region on earth. The results of our analysis indicate that a relationship exists between the ratio of annual mean wave power to mean tidal power and the geomorphic development of clastic coastal depositional environments. Deltas and estuaries are associated with statistically significant differences in mean wave and tidal power. Statistically significant distinctions between populations of deltas, estuaries, strand plains, and tidal flats are also associated with river discharge and river flow rate (defined as discharge divided by open water area). Our results support the hypotheses of previous workers that wave, tide, and river power exert the principal control over the gross geomorphology and facies distribution patterns in clastic coastal depositional environments. Mean values and confidence limits of wave power, tide power, and river flow for the coastal depositional environments targeted in this study may provide a basis for the comparison of modern environments as well as constraints for paleo-reconstructions.

Petrographic characteristics of a Holocene carbonate grainstones in southeast San Salvador, Bahamas: Implications for the sediment reworking in a high energy lagoon

The southeast corner of San Salvador, Bahamas is comprised of several Holocene sedimentary environments in which carbonate sediments are accumulating. Some of these deposits have been lithified to form grainstones, others are not yet lithified. These environments are strand plain (Sandy Hook), dunes (Holocene and Pleistoncene), high energy lagoon (Snow Bay), and tidally-influenced lagoon (Pigeon Creek). These high energy environments are laterally and vertically linked forming different compartments of a carbonate grainstone/packstone body. Petrographic study reveals that these sediments and grainstones are similar in grain composition and texture. The dominant grains are peloids, ooids, and skeletal grains such asHalimeda and foraminifera. Other minor components are bivalves, gastropods, grapestones and intraclasts. Most grains in the Sandy Hook strand plain and the dunes are characterized by abraded grains whereas grains in subtidal sands (Snow Bay and Pigeon Creek) are well preserved. The increasing pattern of ooids with depth in the lagoon and strand plain sediments and the high percentage of ooids in Holocene dune samples suggests that ooid generation occurred early in the Holocene and that subsequently ooids were transported to dunes, and the strand plain. Diagentic characteristics of ooids and also support movement of sand size grains. Clasts in both early and late Holocene deposits are commonly comprised of ooids which are cemented with blocky calcite cement suggesting movement of sediment from one environment (early dune) to other environments including lagoon, beach, and strand plain.

A strand plain soil development sequence in Northern Michigan, USA

A practical problem limiting the theoretical application of a soil chronosequence study lies in the difficulty of identifying an appropriate geomorphic age sequence with more than a few surfaces. A sequence of approximately 75 strand plain beach ridges located along the northern shore of Lake Michigan, USA, overcomes this problem, and was used to explore rates of soil development in the initial stages of podzolization. Well drained pedons were sampled on 24 of the ridges, with an age range of 10 to 5200 years. Chronofunctions were developed using statistical regression techniques. For most forms of extractable Fe and Al, both linear and log–linear functions adequately describe the changes in property with surface age. Dithionite–citrate extractable Fe content, however, shows little correlation with surface age. High r 2 values (>0.7) for chronofunctions representing most extractable sesquioxide forms suggest that B horizon sesquioxide content increases with surface age, as expected for soils undergoing podzolization. Visual inspection of chronofunction data suggests that scatter increases on surfaces older than 3000 years, possibly because soil spatial variability increases with surface age. Theory suggests that the log–linear form of chronofunctions may be preferable to the linear form for these pedons. In general, equation slopes are steeper for chronofunctions representing only the initial 1650 years of soil development than for those representing the entire 5200-year sequence, suggesting that initially rapid pedogenesis slows over time. Most chronofunctions for pH and weighted profile organic C are not statistically significant, possibly because the temporal resolution of the chronosequence is too coarse to detect valid trends for properties that rapidly approach a steady state.

Upper-truncated Power Laws in Natural Systems

— When a cumulative number-size distribution of data follows a power law, the data set is often considered fractal since both power laws and fractals are scale invariant. Cumulative number-size distributions for data sets of many natural phenomena exhibit a “fall-off ” from a power law as the measured object size increases. We demonstrate that this fall-off is expected when a cumulative data set is truncated at large object size. We provide a generalized equation, herein called the General Fitting Function (GFF), that describes an upper-truncated cumulative number-size distribution based on a power law. Fitting the GFF to a cumulative number-size distribution yields the coefficient and exponent of the underlying power law and a parameter that characterizes the upper truncation. Possible causes of upper truncation include data sampling limitations (spatial or temporal) and changes in the physics controlling the object sizes. We use the GFF method to analyze four natural systems that have been studied by other approaches: forest fire area in the Australian Capital Territory; fault offsets in the Vernejoul coal field; hydrocarbon volumes in the Frio Strand Plain exploration play; and fault lengths on Venus. We demonstrate that a traditional approach of fitting a power law directly to the cumulative number-size distribution estimates too negative an exponent for the power law and overestimates the fractal dimension of the data set. The four systems we consider are well fit by the GFF method, suggesting they have properties characterized by upper-truncated power laws.

房総半島九十九里浜平野の海浜堆積物から求めた過去６０００年間の相対的海水準変動と地震隆起

Relative sea-level changes and variations in shoreline progradation rate over the past 6000 years are elucidated from the elevations of the beach deposits, their 14C ages, and the geographic position of each locality on the Kujukuri strand plain, Pacific coast of the Boso Peninsula, central Japan. These past sea-levels were +4 to +6 m above the modern sea-level (high-stand stage) at 6000 to 5300 calendar years B.P., +3 to + 4.5 m (stable stage) at 5000 to 3500 years B.P., declined from +1.2-+ 3.4 m to + 0.5-+ 2.1 m (falling stage) at 3300 to 2250 years B.P., and were-1.5--1 m to + 1 m (stable stage) from 1650 to 250 years B.P. ; sea level is 0 m at present. The detailed changes revealed by this new method strongly imply the existence of several rapid uplifts (0.4 to 1.2 m per event) at 5100 to 5500 years B.P., 3400 years B.P., 2400 years B.P., 1650 years B.P., and 0-250 years B.P. The uplifts were co-seismic, because the speed of occurrence seems to have been high, and the events are generally associated with so-called “tsunami deposits.” Co-seismic uplift in this region has not been reported previously from historical records or geological evidence.

ABSTRACT: Sequence Stratigraphic Analyses of the Upper Cretaceous Deposits, Rio Grande Embayment, Using Well Logs, Cores and Outcrops

ABSTRACT The present study is an attempt to solve problems of stratigraphic correlation in the Upper Cretaceous strata, Rio Grande Embayment, using sequence stratigraphic principles applied to cores, outcrops and wireline log information. Well-defined log signatures, supplemented by core and outcrop data, were observed and correlated between boreholes. Chronostratigraphically significant surfaces, especially transgressive surfaces, were correlated. Upward-coarsening sand units within the three Upper Cretaceous progradational wedges, San Miguel, Olmos and Escondido formations, encased in prodelta and shelf mudstones were laterally correlated through the study area. Observations indicate a basinward decrease in number of sand units and net sandstone thickness. Outcrop studies in Maverick County indicate deposition of the coal-bearing Olmos Formation in the lower deltaic plain whose upper part is eroded and unconformably overlain by transgressive units of the Escondido Formation. Cored intervals through reservoir-quality clean and mature sandstones from the San Miguel Formation confirm long reworking history by wave action and longshore currents forming strand plain deposits within a wave dominated deltaic setting. Cores sampled in the updip position indicate more tight and argillaceous sandstones with more fluvial influence and low reservoir potential. Downdip Olmos and Escondido formations were interpreted to belong to a transgressive systems tract. Updip Olmos, a coal-bearing sandstone and shale sequence of coastal-plain and deltaic origin, is more argillaceous and low reservoir quality and belongs to a highstand systems tract. End_of_Record - Last_Page 4-------

Mineral Sands Occurrences in the Murray Basin, SoutheasternAustralia

The Murray Basin in southeastern Australia is proving to be a major mineral sand province that eventually will replace Australia’s east and west coasts in production of rutile, zircon, and ilmenite. Concentrations of relatively coarse-grained heavy mineral occur as beach placers in the Pliocene Loxton-Parilla sands in the upper part of the Murray Basin sequence. These formed as 400-km-long barrier complexes in the Murravian Gulf under the action of long-period ocean swell waves. We think the main source of barrier sand, at least initially, was from erosion of Miocene sands on the bed of the Murravian Gulf; progradation was a response to sea level fluctuations linked to Milankovitch climatic cycles in the Pliocene. In most areas, the resulting 400-km-wide barrier strand plain is now overlain by fluvial, aeolian, and lacustrine deposits. Typically, the heavy mineral deposits are ilmenite rich, with 30 to 40 percent rutile and zircon. They occur as single, or as multiple, stacked strandline deposits, are often more than 10 m thick, have mineral grades that exceed 20 percent in places, are several hundred meters wide and 10 to 25 km long; some contain up to several million tonnes of heavy mineral. The rutile and zircon are comparable in grain size and quality to minerals traditionally mined in Australia. Many of the deposits are associated with topographic ridges—the Neckarboo and Iona Ridges are the best known—that appear to be fault-bounded blocks. Deposits of major commercial significance found so far contain a total of over 12 million tonnes (Mt) of rutile, zircon, and ilmenite. The total, coarse-grained mineral sand resources in the Murray Basin are conservatively estimated to be over 50 Mt. The distribution of mineral sands in the Murray Basin seems to be associated with two aspects of the region’s geology and geomorphology: (1) a zone bordering the central part of the basin where the Pliocene barriers were derived from underlying Miocene sands that probably already contained some mineral concentrations and (2) growth faulting with deposits preferentially occurring on upfaulted blocks especially in the zone defined by (1) above. We speculate that localized uplift during the formation of the Loxton-Parilla barriers was sufficient to modify coastal processes on uplifted blocks so as to increase the rate of alongshore sediment bypass compared to nearby areas. This phenomenon has been simulated in computer modeling. Where the barrier sands were already enriched in heavy minerals, winnowing by storm waves formed beach placers on the uplifted fault-blocks. Based on criteria (1) and (2), the prospective areas of the Murray Basin account for 80 percent of the beach placers found to date.

ABSTRACT: A Re-Evaluation of the Hackberry--New Life for a Comatose Trend

Abstract The Oligocene Hackberry trend of southeast Texas and southwest Louisiana has posed one of the Gulf Coast's most perplexing targets for petroleum exploration. Thick, high-quality pays and moderate drilling depths have lured many explorationists to try to unlock its potential. However, reservoir extent has, in the past, been unpredictable. The play was all but abandoned during the late 1980s and early 1990s. A regional re-evaluation of the geologic model arose from the assimilation of well log correlations, dipmeter use and evaluation, interpretation of paleontological reports, and the combination of quality 2-D seismic data. From this work it became very apparent that the majority of the trend should be interpreted as a sub-unconformity/slump block play and not a deep-marine, basin-floor/turbidite sequence. The new model predicted reservoir extent and thickness concisely and logically. The history of the trend is one of prograding shallow-marine deposition from the lower Frio Formation through the Nodosaria blanpiedi and Nonion struma zones, followed by thick shallow-water deposition of up to 500 feet of strand plain sands in the upper Frio Formation. Basin collapse, resulting from regional salt withdrawal and development of salt domes, caused over-steepening of the sea floor. The result was slumping of the soft sediments from the underlying Vicksburg Formation through the early Upper Frio strand plain deposits. Wave-base erosion removed most of the youngest sand section. The erosion was followed by marine shale deposition containing the diagnostic Hackberry faunal assemblage. As subsidence ceased and the basin finally filled with shale, shallow-marine strand plain deposition continued through deposition of the upper Frio section. Armed with this geologic model, a group of industry partners partook to gather regional 3-D seismic coverage in order to take advantage of more than 500 undrilled square miles that still existed in the trend. Eventually the effort resulted in 25 successful wells out of 30 attempts. End_of_Record - Last_Page 281-------

Rapid strand-plain accretion in the northeastern Nile Delta in the 9th century A.D. and the demise of the port of Pelusium

Research Article| February 01, 1999 Rapid strand-plain accretion in the northeastern Nile Delta in the 9th century A.D. and the demise of the port of Pelusium Glenn A. Goodfriend; Glenn A. Goodfriend 1Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road, N.W., Washington, D.C. 20015, USA Search for other works by this author on: GSW Google Scholar Daniel Jean Stanley Daniel Jean Stanley 2Deltas—Global Change Program, Paleobiology E-206, U.S. National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Glenn A. Goodfriend 1Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road, N.W., Washington, D.C. 20015, USA Daniel Jean Stanley 2Deltas—Global Change Program, Paleobiology E-206, U.S. National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, USA Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1999) 27 (2): 147–150. https://doi.org/10.1130/0091-7613(1999)027<0147:RSPAIT>2.3.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Glenn A. Goodfriend, Daniel Jean Stanley; Rapid strand-plain accretion in the northeastern Nile Delta in the 9th century A.D. and the demise of the port of Pelusium. Geology 1999;; 27 (2): 147–150. doi: https://doi.org/10.1130/0091-7613(1999)027<0147:RSPAIT>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract An unusually large (∼1 km3) and rapid influx of Nile River sediment in the early 800s (a.d.) resulted in accretion of an extensive strand plain (6 to 15 m thick, 35 km long, and as much as 12 km wide) on the subsiding northeastern Nile Delta margin, Egypt. This event is related to blockage of the Pelusiac branch and breaking through of a new distributary to the west of present-day Port Said, probably representing initiation of the Damietta branch. The sand is of analytically identical age throughout the area and was deposited within less than ∼60 yr, as indicated by 14C and amino acid racemization analyses of Donax shells from a series of cores. Radiocarbon dates, in combination with historical accounts by Al-Jakubi, who found the strand plain already in existence when he visited the area in the late 800s, place this event in the early 800s. Nilometer flood records suggest that the sequence of great floods of 813, 816, and 820 may have been the triggering events. This sudden displacement of sand caused Pelusium, then the principal port and fortified city of the northeastern Nile Delta located at the mouth of the Pelusiac branch, to be cut off from both the Nile and the Mediterranean, and led to its decline and eventual abandonment by the 12th century, when the Crusaders arrived. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Coastal zone of The Gambia and the Abidjan region in Côte d'Ivoire: sea level rise vulnerability, response strategies, and adaptation options

The aerial videotape-assisted vulnerability analysis (AVVA) technique was combined with various data sets to assess the vulnerability of the coastal zone of The Gambia to sea level rise. Land loss due to inundation, flooding, and erosion was estimated. Costs of damage and population at risk were also evaluated. Only historical data and maps were used to assess the vulnerability of the coastal zone of the Abidjan region of Cote d'Ivoire to sea level rise. Results show that with a 1 m sea level rise the whole of the capital city of Banjul will be under mean sea level in the next 50 to 60 yr as a greater part of the city is below 1 m. The mangrove systems on St. Mary's Island, Kombo St. Mary, and the strand plains in the north bank will be inundated. About 1950 billion Dalasis (US $ 217 million) worth of land will be lost. The most appropriate response would be to protect the whole of the coastline of Banjul, the shoreline area from the Banjul cemeteries to Laguna Beach Hotel, the infrastructure at Sarro, and the hotel complex at Cape Point. Innovative sand management, repair of the damaged groins, and construction of dikes, breakwater structures, revetments, and low-cost seawall are some of the shoreline stabilization and hardening techniques suggested for the protection of this area. For the Abidjan region, the same response strategies should be used. Adaptation responses identified for both regions include public awareness, increase in height of coastal infrastructure, urban growth planning, wetland preservation and mitigation, and development of a coastal zone management plan.

Strand-plain evidence for late Holocene lake-level variations in Lake Michigan

Lake level is a primary control on shoreline behavior in Lake Michigan. The historical record from lake-level gauges is the most accurate source of information on past lake levels, but the short duration of the record does not permit the recognition of long-term patterns of lake-level change (longer than a decade or two). To extend the record of lake-level change, the internal architecture and timing of development of five strand plains of late Holocene beach ridges along the Lake Michigan coastline were studied. Relative lake-level curves for each site were constructed by determining the elevation of foreshore (swash zone) sediments in the beach ridges and by dating basal wetland sediments in the swales between ridges. These curves detect long-term (30+ yr) lake-level variations and differential isostatic adjustments over the past 4700 yr at a greater resolution than achieved by other studies. The average timing of beach-ridge development for all sites is between 29 and 38 yr/ridge. This correspondence occurs in spite of the embayments containing the strand plains being different in size, orientation, hydrographic regime, and available sediment type and caliber. If not coincidental, all sites responded to a lake-level fluctuation of a little more than three decades in duration and a range of 0.5 to 0.6 m. Most pronounced in the relative lake-level curves is a fluctuation of 120–180 yr in duration. This ≈150 yr variation is defined by groups of four to six ridges that show a rise and fall in foreshore elevations of 0.5 to 1.5 m within the group. The 150 yr variation can be correlated between sites in the Lake Michigan basin. The ≈30 and 150 yr fluctuations are superimposed on a long-term loss of water to the Lake Michigan basin and differential rates of isostatic adjustment.

Origin of beach ridges: Comment on Tanner, W.F., 1995. Origin of beach ridges and swales. Mar. Geol., 129: 149–161

Tanner (1995) has proposed that most common strand plain sandy beach ridges (his swash-built type) have been formed by a sea level rise-and-fall couplet of 5–30 cm, with a periodicity which is most commonly 30–60 years, but which ranges from as little as 3 to as much as 60 years. While such a mechanism could perhaps apply to beach ridges in lakes, if sea level has fluctuated with such regularity for the past several thousand years, all open ocean beach ridge periodicities should be the same, and furthermore this sea level signal would surely have been detected by physical oceanographers. Curray et al. (1969) described a strand plain of several hundred beach ridges on the western Mexican coast with cyclic formation of ridges varying from 12.2 to 16.5 years. The mechanism of formation invoked was periodic building of offshore bars to above sea level after sufficient sand had been transported into the area and during an optimal combination of oceanographic conditions.

Influence of relative sea-level on facies and reservoir geometry of the Middle Jurassic lower Brent Group, UK North Viking Graben

Abstract Detailed sequence stratigraphy of several neighbouring fields in the East Shetland basin indicates that a higher order of cyclicity is superimposed onto the lower Brent Group. Both relative falls and rises in sea-level affected the strongly progradational nearshore/barrier-island system and induced important variations in the geometry, distribution and stacking patterns of the reservoir facies. The majority of the shallow marine strata belong to the transgressive and highstand systems tract and consist of the lower-shoreface Rannoch, the upper shoreface and strand-plain Etive and the back-barrier and lagoonal Lower Ness. High frequency increments of shoreline progradation are preserved in the Rannoch as gently seaward-dipping bedsets. The small-scale units mark asymmetric cycles in grain size and mica content and together, with stratiform cement, impart a strong permeability anisotropy on the Rannoch. The nearshore Etive Formation represents a sediment-laden, barred nearshore complex and is subdivided into (1) a uniformly thick upper shoreface and (2) an overlying emergent strand plain. The two subfacies are commonly separated by a thin interval of foreshore which is locally enriched in heavy minerals. The shoreface deposits show systematic variations in stacking geometries ranging from strongly progradational to aggradational. Two relative falls in sea-level led to the subaerial erosion of nearshore Etive deposits and the juxtaposition of coastal-plain mudstones, coals and fluvial deposits with shale-clast lags on lower shoreface Rannoch strata. Although lithostratigraphically part of the Etive, these deposits bear no resemblance to the well ordered nearshore-Etive deposits. The channel complexes are vertically and laterally heterogeneous and are confined to incised valleys separated by non-depositional interfluves. In Cormorant and Tern fields, well-performance anomalies such as early water breakthrough and unpredictable water injection and oil production rates are associated with these lowstand incised valley deposits. An enigmatic coarse-grained unit occurs in the lower Rannoch in Eider field and is provisionally interpreted as the distal expression of the lowstand shoreface deposits associated with the older incised valley. Following the lowstand deposition nearshore-marine sedimentation reestablished during the transgressive/early highstand systems tract. Under the influence of rising relative sea-level the barrier complex aggraded in place with minimal landward translation of the shoreline position. The volume of sediment supplied to the Etive shoreface was sufficiently high to keep pace with phases of increased accommodation. The shoreline system subsequently stacked with a strongly progradational geometry as the high sediment supply filled the available accommodation space during the latter part of the highstand systems tract.

Quaternary crustal movements examined from facies distribution in the Atsumi and Hamana areas, central Japan

Quaternary sediments are distributed from the east coast of Lake Hamana to the Atsumi Peninsula, on the Pacific side of central Japan. The sediments in the eastern Hamana area include fluvial, estuary and deltaic facies, whereas sediments in the western Atsumi area include fluvial, estuary, shoreface, beach and coastal marsh facies. The sediments in the Hamana area comprise four sedimentary units; those in the Atsumi area comprise seven sedimentary units. Each unit in the Hamana area was formed by the alternation of a transgressive estuary system and a regressive fan-delta system. In contrast, each unit in the Atsumi area was formed by the alternation of a transgressive estuary system and a regressive fan-delta system. In contrast, each unit in the Atsumi area was formed by the alternation of a transgressive estuary system and a regressive strand plain system. Stratal correlation with the ocean oxygen isotope variation indicates that the four younger units in both areas can be correlated and that the five younger units were formed at the sea-level maxima during interglacial stages, the oxygen isotope stages being 1, 5, 7, 9 and 11. The top of each sequence is marked by the beach or fluvial facies, deposited during highstand, the present altitude of which was used as a marker for the palaeo-highstand sea-level. A record of palaeo-highstand sea-level change was obtained from five locations in the Atsumi area and one location in the Hamana area. Comparison of the palaeo-highstand sea-level changes with the glacio-eustatic highstand sea-level change, determined from raised coral reef terraces, shows that the Atsumi area subsided at the mean rate of 27 cm/1000 yr until 331,000 yr B.P. and the whole area was then uplifted between 331,000 and 122,000 yr B.P., with a maximum uplift rate of 29 cm/1000 yr. The differential crustal movements were more active in the latter period. The wavelength of the crustal bending is estimated at 50–100 km and the amplitude of the bending was less than 10 m before 331,000 yr B.P. and was 50 m thereafter. The change in vertical crustal movement is synchronous in Japan, New Zealand and New Guinea. Such a synchronous change in the vertical crustal movement may be explained by a change in the regional horizontal stress field due to rotation of the Pacific plate.

Sedimentation and Lithofacies Relations in the Holocene Pahang Delta Complex, East Coast Malay Peninsula, Malaysia: ABSTRACT

A detailed study of the Pahang River Delta was undertaken in order to understand the development, architecture, geometrical characteristics, and structural sequential organization of the sand bodies on the east coast of the Malay Peninsula. The present delta indicates that although marine wave regimes are dominant, as exhibited by the cuspate-shaped delta, fluvial and tidal influences are substantial, as evident from the bedforms and sand bars morphology. The Pahang Delta system provides a unique case study for a tropical fluvio-marine windwave-dominated delta, which was profoundly influenced by seasonal storms. The deltaic sand is coarse and moderately sorted, and contains abundant clay clasts. The southern coastline of the Pahang Delta is continuously modified by the erosive attack of the storm waves. The delta is subjected to extremely high-energy storm waves and fluvially formed sand bodies, such as channel mouth bars, dominant in other types of deltas that have been replaced by strand plains, sand bars and sand flats. The combination of high wave energy and strong littoral drift along the east coast of the Malay Peninsula results in changing the orientation of the sand bodies in the Pahang Delta. No modern wind-dominated delta is comparable to the Pahang Delta system. However,more » some modern deltas show many similarities in general morphology and sand distribution. The authors have developed a comprehensive sedimentological model of fluvio-marine sand-body variability in tropical wind-dominated deltas. The results of the studies will enlarge the applicability of geometrical studies to subsurface exploration of hydrocarbons.« less

シーケンス層序学 アブダビ海域Ｎｅｅｗａｔ Ａｌ Ｇｈａｌａｎ （ＧＡ）油田におけるＡｒａｂ・Ｈｉｔｈ層（ジュラ系）中のＨＳＴとＴＳＴ ＧＡ油田における堆積サイクルと積み重なりパターン

The depositional sequence in the Upper Jurassic Arab•Hith Formations, which is main reservoir zone of the Neewat Al Ghalan (GA) field, offshore Abu Dhabi, is composed of sabkha-nearshore deposits and divided into two systems tracts (transgressive systems tract (TST) and highstand systems tract (HST)) based on the characteristics of parasequence stacking patterns.Each parasequence in TST shows a shallowing upward cycle which commences from barrier shoal grainstone and terminates in lagoonal mudstone or sabkha anhydrite. Vertical stacking patterns of these parasequences within TST indicate thinning upward cycle and retrogradational/aggradational pattern.The parasequences in HST are characterized by a shallowing upward cycle from tidal channel grainstone or lagoonal mudstone to sabkha anhydrite. Stacking patterns of both bedsets parasequences within HST show overall thickening upward cycles and progradational pattern.The stacking patterns in the depositional sequence reflect various orders of sea level fluctuations. During TST deposition the barrier shoal systems accompanied by shoreface erosion developed in the field. In the succeeding HST deposition, the barrier shoal (strand plain) systems were migrating basinward, and the tidal flat-sabkha systems, in turn, were prograding to the field. These environmental changes due to the sea level fluctuations are considered to have affected the reservoir quality (cementation or dolomitization) of the field.

Sequence Stratigraphy of the Upper Pennsylvanian Cleveland Formation: A Major Tight-Gas Sandstone, Western Anadarko Basin, Texas Panhandle

The Upper Pennsylvanian (lower Missourian) Cleveland formation has yielded 459 bcf of natural gas and 18.6 million bbl of oil from low-permeability (<0.10 md) fluvial and deltaic reservoirs in a seven-county tight-gas area of the northeastern Texas panhandle. Regional study of the Cleveland and underlying Desmoinesian Marmaton Group siliciclastics using tight well control and cores established the sequence-stratigraphic framework to clarify the vertical and areal occurrence of Cleveland reservoirs, seals, and possible source rocks. Regionally distinctive facies stacking patterns in the study interval compose a sequence-stratigraphic framework of several westerly sourced systems tracts and three depositional sequences (S). S1 is characterized by landward- and seaward-stepping deltaic and strand plain cycles (parasequences) deposited on the top-of-Oswego type 1 sequence boundary that define (in ascending order) Marmaton late-stage lowstand-wedge (LST:pw) and transgressive systems tracts (TST) and a lower Cleveland highstand systems tract (HST). A regionally correlative, organic-rich marine-condensed section at the top of the Marmaton TST, equivalent to the Nuyaka Creek black shale bed of mid-continent cyclothems, represents maximum flooding conditions during eustatic rise. A relative sea level drop with the onset f S2 deposition initiated development of a lowstand incised-valley system (LST:iv) in the middle to upper Cleveland that extended basinward of the lower Cleveland depositional shelf edge. Subsequent coastal onlap by thin deltaic systems of the overlying TST marks the start of decreased sediment influx during late Cleveland time, resulting in thinning of parasequences and an increase in carbonate beds of high-frequency cycles in upper S2 and S3. Stratigraphic traps and pinch-out of reservoir facies within small, southeast-plunging anticlines make up most traps in the producing area. Proximal delta-front and fluvial sandstones of the Cleveland upper HST and overlying LST:iv, respectively, are the primary reservoirs. The high-total-organic-carbon, top-of-Marmaton marine-condensed section and thick prodeltaic and lower distal delta-front shales within the lower Cleveland HST are the probable source rocks. Distal deltaic shales of the middle Cleveland TST form most reservoir seals. Potential new reservoirs should be targeted at the updip terminations of systems tracts, at lap-out positions of individual sand-rich HST and TST parasequences, and along LST:iv valley-margin stratal terminations.

The space-time structure of oil and gas field growth in a complex depositional system

Shortly after the discovery of an oil and gas field, an initial estimate is usually made of the ultimate recovery of the field. With the passage of time, this initial estimate is almost always revised upward. The phenomenon of the growth of the expected ultimate recovery of a field, which is known as “field growth,” is important to resource assessment analysts for several reasons. First, field growth is the source of a large part of future additions to the inventory of proved reserves of crude oil and natural gas in most petroliferous areas of the world. Second, field growth introduces a large negative bias in the forecast of the future rates of discovery of oil and gas fields made by discovery process models. In this study, the growth in estimated ultimate recovery of oil and gas in fields made up of sandstone reservoirs formed in a complex depositional environment (Frio strand plain exploration play) is examined. The results presented here show how the growth of oil and gas fields is tied directly to the architectural element of the shoreline processes and tectonics that caused the deposition of the individual sand bodies hosting the producible hydrocarbon.

The 1-AB Block Fields: A Giant Oil Accumulation in Eastern Peru

The 1-Ab block fields are located in the northeastern part of Peru. Geologically, the area is the sub-Andean Maranon Basin, a continuation of the Napo Basin from eastern Ecuador. During the 20 years that Occidental has operated Block 1-AB, approximately 11,500 km of seismic data has been recorded and 34 exploratory wells have been drilled, resulting in the discovery of 18 fields, or 53% exploration success. The 1-AB oil accumulation discovered in 1972 is a group of medium to small asymmetric anticlines distributed along six northwest-southeast trending structural alignments: North Capahuari-South Capahuari-Tambo, Carmen-North San Jaacinto and Bartra. This concentration of productive structures in a relative small area is unique within the Maranon basin. The controlling factors include exceptional pre-Cretaceous uplifting and the presence of very good to excellent Cretaceous sandstones reservoirs. The two major Cretaceous producing zones, the Chonta and Vivian sandstones, have been defined within the Coniacian and Campanian ages respectively. The Chonta sands are related to shelfal deposition across Block 1-AB, represented by strand plain and barrier island sediments. The Vivian formation is a massive fluvial sandstone covering all of the Maranon basin and ranging in thickness between 40 and 200 feet. After oil was accumulated, fresh watermore » influxes into the reservoirs of the northern and eastern fields caused oil biodegradation and salinity variation of the reservoir waters, depending upon the intensity of biodegradation. Oil remigration also has been documented for the South Huayari field.« less

Quartz Grain Surface Textures as Indicators of Depositional History of Beach and Strand Plain Sediments Along the North Kerala Coast

Abstract SEM analysis of quartz grain surfaces from the strand plain show many of the characteristic textures that are produced under sub-aqueous environments with second generation features of wind action. It is inferred that the initial stage of deposition of the strand plain sediments was associated with a wave dominated environment. With emergence of this coast, the strand plain sediments were exposed to sub-aerial action, thus registering both sub-aqueous and sub-aerial action features.