Sea Level Lowstand Features of the Shelf Margin Off Southwestern Louisiana

1987 ◽  
pp. 225-240 ◽  
Keyword(s):  
Sea Level ◽  
Shelf Margin

Shelf and Shelf-Margin Growth in Scenarios of Rising and Falling Sea Level

2008 ◽  
pp. 47-71 ◽  
Author(s):  
RONALD J. STEEL ◽  
CRISTIAN CARVAJAL ◽  
ANDREW L. PETTER ◽  
CARLOS UROZA
Keyword(s):  
Sea Level ◽  
Shelf Margin

The arrival of the paleo–Orinoco Delta at Trinidad: The Cruse Formation delta lobes and delivery to deepwater Atlantic

2020 ◽  
Vol 90 (8) ◽  
pp. 938-968
Author(s):  
Ariana Osman ◽  
Ronald J. Steel ◽  
Ryan Ramsook ◽  
Cornel Olariu ◽  
Si Chen
Keyword(s):  
Sea Level ◽  
Late Miocene ◽  
Sediment Supply ◽  
Average Height ◽  
Shelf Edge ◽  
Sea Level Changes ◽  
Orinoco Delta ◽  
Basin Floor ◽  
Shelf Margin ◽  
High Sediment

ABSTRACT Icehouse continental-shelf-margin accretion is typically driven by high-sediment-supply deltas and repeated glacio-eustatic, climate-driven sea-level changes on a ca. 100 ky time scale. The paleo–Orinoco margin is no exception to this, as the paleo–Orinoco River Delta with its high sediment load prograded across Venezuela, then into the Southern and Columbus basins of Trinidad since the late Miocene, depositing a continental-margin sedimentary prism that is > 12 km thick, 200 km wide, and 500 km along dip. The Cruse Formation (> 800 m thick; 3 My duration) records the first arrival of the paleo–Orinoco Delta into the Trinidad area. It then accreted eastwards, outwards onto the Atlantic margin, by shallow to deepwater clinoform increments since the late Miocene and is capped by a major, thick flooding interval (the Lower Forest Clay). Previous research has provided an understanding of the paleo–Orinoco Delta depositional system at seismic and outcrop scales, but a clinoform framework detailing proximal to distal reaches through the main fairway of the Southern Basin has never been built. We integrate data from 58 wells and outcrop observations to present a 3-D illustration of 15 mapped Cruse clinoforms, in order to understand the changing character of the first Orinoco clastic wedge on Trinidad. The clinoforms have an undecompacted average height of 550 m, estimated continental slope of 2.5° tapering to 1°, and a distance from shelf edge to near-base of slope of > 10 km. The clinoform framework shows trajectory changes from strong shelf-margin progradation (C10–C13) to aggradation (C14–C20) and to renewed progradation (C21–24). Cruse margin progradational phases illustrate oblique clinothem geometries that lack well-developed topsets but contain up to 70 m (200 ft) thick, deepwater slope channels. This suggests a high supply of sediment during periods of repeated icehouse rise and fall of eustatic sea level, with fall outpacing subsidence rates at times, and delivery of sand to the deepwater region of the embryonic Columbus channel region. Also, evidence of wholesale shelf-edge collapse and canyon features seen in outcrop strongly suggest that deepwater conduits for sediment dispersal and bypass surfaces for Cruse basin-floor fans do exist. The change to a topset aggradational pattern with a rising shelf trajectory may be linked to increased subsidence associated with eastward migration of the Caribbean plate. The Cruse-margin topsets were dominated by mixed fluvial–wave delta lobes that were effective in delivery of sands to the basin floor. The preservation of a fluvial regime of the delta may have been impacted by basin geometry which partly sheltered the area from the open Atlantic wave energy at the shelf edge. Ultimately, understanding shelf-edge migration style as well as process-regime changes during cross-shelf transits of the delta will help to predict the location of bypassed sands and their delivery to deepwater areas.

Permian trilobites from West Texas

1992 ◽  
Vol 66 (6) ◽  
pp. 924-943 ◽  
Author(s):  
David K. Brezinski
Keyword(s):  
Shallow Water ◽  
Sea Level Rise ◽  
Sea Level ◽  
Late Permian ◽  
West Texas ◽  
Deep Waters ◽  
Shelf Margin

Trilobites occur in two generically distinct faunas in the Permian strata of West Texas. The stratigraphically lower fauna, composed of Ditomopyge decurtata (Gheyselinck), Ditomopyge sp., Triproetus angustus n. sp., Triproetus tumidus n. sp., Triproetus altasulcus n. sp., is present in Wolfcampian and early Leonardian strata. The stratigraphically upper fauna, present in late Leonardian and Guadalupian strata, is comprised of Delaria antiqua (Girty), Delaria granti n. sp., Delaria brevis n. sp., Delaria westexensis n. sp., Delaria chinatiensis n. sp., Novoameura vitrumons n. sp., Anisopyge perannulata (Shumard), and Anisopyge cooperi n. sp.The lower fauna originated in the late Pennsylvanian, inhabited shallow-water environments, was relatively pandemic, and is interpreted to have become extinct as a result of marine regression during the early to middle Leonardian. The endemic upper fauna originated in deep waters of the Marfa and Delaware Basins during the late Leonardian, and, concurrent with sea level rise, migrated and diversified into the shelf-margin reefs of the late Leonardian and Guadalupian. Regression during the Late Permian resulted in extinction of this second Permian trilobite fauna.

scholarly journals RECOGNIZING LATE CRETACEOUS TO PALEOGENE CHANGES IN RELATIVE SEA LEVEL IN NORTHERN SANTOS BASIN, BRAZIL

2019 ◽  
Vol 37 (2) ◽  
Author(s):  
A.M. Garcia ◽  
C.A. Pires ◽  
D. Münch ◽  
I. F.P Carvalho ◽  
L.S Freitas ◽  
...  
Keyword(s):  
Sea Level ◽  
Higher Order ◽  
Seismic Facies ◽  
Relative Sea Level ◽  
Seismic Section ◽  
Basin Scale ◽  
System Tracts ◽  
Mass Transport Deposits ◽  
Order Sequence ◽  
Shelf Margin

ABSTRACT. The stratigraphy of the Santos Basin has become of great interest in the last decade because of the large oil accumulations in pre-salt (rift) and post-salt (drift) strata. Nevertheless, the most accepted stratigraphic models for the drift phase are only at a basin scale and can still be improved by more detailed work. In this paper we analyze an inline seismic section in the modern continental slope of the Santos Basin in order to describe the stratigraphy and to reconstruct relative-sea level (RSL) changes from the Campanian to the Eocene/Oligocene boundary. We mapped 40 seismic horizons, in which clinoform rollovers (former shelf margins) and stratal terminations were recognized. These data allowed for the construction of a chronostratigraphic chart and a RSL curve. The proposed stratigraphic chart displays three lower-order sequence sets comprising higher-order sequences including mostly alternating forced-regressive and normal-regressive system tracts, with the exception of three important transgressive episodes. Higher-order sequences above the intra-Maastrichtian unconformity exhibit low-angle ascending to descending shelf-margin trajectories and frequently truncated topsets, while aggradation was more important during Campanian to Maastrichtian. Expressive mass-transport deposits (chaotic seismic facies) at the bottomsets of some mapped horizons all match with forced-regressive episodes.Keywords: seismic interpretation, sequence stratigraphy, shelf-margin clinoforms.RESUMO. A Bacia de Santos tornou-se de grande interesse na última década devido às acumulações de petróleo no pré-sal (rifte) e pós-sal (deriva). No entanto, os modelos estratigráficos mais aceitos para a fase de deriva são em escala de bacia e podem ser incrementados por trabalhos de maior detalhe. Analisamos uma seção sísmica longitudinal no talude continental atual da bacia, a fim de descrever a estratigrafia e reconstruir mudanças do nível relativo do mar (NRM) do Campaniano ao limite Eoceno/Oligoceno. Quarenta horizontes sísmicos foram mapeados, nos quais margens da plataforma (clinoform rollovers) e terminações estratais foram reconhecidas. Esses dados permitiram a construção de um diagrama cronoestratigráfico e uma curva de variação do NRM. Identificou-se três conjuntos de sequências de menor ordem compreendendo sequências de ordem mais elevada, incluindo, na sua maioria, alternância entre regressão forçada e normal, com exceção de três importantes episódios transgressivos. As sequências de maior ordem acima da inconformidade intra-Maastrichtiano exibem trajetórias ascendentes de baixo ângulo a descendentes de margem de plataforma e topsets truncados, enquanto agradação foi mais importante entre o Campaniano e o Maastrichtiano. Depósitos de transporte de massa (fácies sísmicas caóticas) nos bottomsets de alguns horizontes mapeados associam-se com episódios de regressão forçada.Palavras-chave: interpretação sísmica, estratigrafia de sequências, clinoformas de margem de plataforma.

scholarly journals A forced regressive shelf-margin wedge formed by transition-slope progradation: lowermost Cretaceous Rauk Plateau Member, Jameson Land, East Greenland

2005 ◽  
Vol 52 ◽  
pp. 227-243 ◽  
Author(s):  
F. Surlyk
Keyword(s):  
Sea Level ◽  
Large Scale ◽  
Coarse Grained ◽  
Shelf Edge ◽  
High Angle ◽  
Seismic Profiles ◽  
East Greenland ◽  
Shelf Slope ◽  
Forced Regression ◽  
Shelf Margin

The Middle Jurassic – lowermost Cretaceous succession of Jameson Land, East Greenland records a marine, overall regressive–transgressive–regressive cycle with regressive maxima in the Late Bajocian and Late Volgian separated by a transgressive maximum in the Kimmeridgian. Smaller-scale regressive interludes took place in the Late Callovian and Mid Oxfordian. A shelf-slope-basin physiography started to develop in the Late Callovian due to increasing rifting and a relief of several hundred metres was attained during maximum end-Jurassic regression and deposition of the Volgian Raukelv Formation. The formation consists of a forestepping stack of laterally extensive shelf-edge wedges, each several tens of metres thick, composed of coarse-grained sandstone, showing highangle clinoform bedding and containing marine body and trace fossils. These clinoform beds are superimposed on the large-scale clinoforms of the shelf–slope–basin. The wedges onlap older shelf deposits in a landward direction and are overlain by thin transgressive sandstones or mudstones, or directly by the next coarse-grained wedge. The top wedge, comprising the Rauk Plateau Member, is of Late Volgian (i.e. earliest Cretaceous) age and is characterized by steep clinoforms truncated by internal erosional downlap surfaces. The clinoforms are simple avalanche beds, a few tens of centimetres thick, or they may be several metres thick and contain large-scale cross-bedded intrasets of probable tidal origin. The erosional events were associated with downshift of the succeeding clinoforms, recording minor sea-level fall and forced regression. The top surface of the Rauk Plateau wedge is incised by a system of minor channels leading to a large canyon-like valley. The wedge was deposited by transition-slope progradation below wave base during a period of sea-level stillstand punctuated by minor, stepwise falls. It provides an excellently exposed example of a laterally derived, coarse-grained shelf-margin wedge, showing high-angle clinoform bedding and representing an ancient counterpart to Holocene and Late Pleistocene prograding infralittoral wedges seen on seismic profiles across Mediterranean shelf edges.

Note on Selection of Coordinate Systems for Geodynamics

1975 ◽  
Vol 26 ◽  
pp. 395-407
Author(s):  
S. Henriksen
Keyword(s):  
Sea Level ◽  
The Other ◽  
Coordinate Systems ◽  
Mean Sea Level ◽  
The Earth ◽  
The One ◽  
Static Systems ◽  
Selection Of

The first question to be answered, in seeking coordinate systems for geodynamics, is: what is geodynamics? The answer is, of course, that geodynamics is that part of geophysics which is concerned with movements of the Earth, as opposed to geostatics which is the physics of the stationary Earth. But as far as we know, there is no stationary Earth – epur sic monere. So geodynamics is actually coextensive with geophysics, and coordinate systems suitable for the one should be suitable for the other. At the present time, there are not many coordinate systems, if any, that can be identified with a static Earth. Certainly the only coordinate of aeronomic (atmospheric) interest is the height, and this is usually either as geodynamic height or as pressure. In oceanology, the most important coordinate is depth, and this, like heights in the atmosphere, is expressed as metric depth from mean sea level, as geodynamic depth, or as pressure. Only for the earth do we find “static” systems in use, ana even here there is real question as to whether the systems are dynamic or static. So it would seem that our answer to the question, of what kind, of coordinate systems are we seeking, must be that we are looking for the same systems as are used in geophysics, and these systems are dynamic in nature already – that is, their definition involvestime.

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