Felber, J., Hoffmann, R., Leinfelder, R. & Oschmann,W. (1982):

Biofaziesanalyse randmariner Ablagerungsbereiche im Oberen Jura Portugals.
II.Paläogeographie und Faziesverteilung in der Serra da Arrabida.-

Biofacies analysis of Upper Jurassic marginally marine environments of Portugal. II Paleogeography and facies distribution of the Serra da Arábida region.

N. Jb. Geol. Paläont., Abh., 163: 301-330; Stuttgart.

Abstract

The Upper Jurassic sediments of the Serra da Arrábida (Estremadura, Portugal) are classified lithologically and eleven facies types are distinguished. The distribution in space and time is reconstructed. The facies types range from terrestrial clasts, caliche crusts, brackish lagoons to tidal deposits and shallow marine biomicrites, nodular limestones, coral biostromes, intraclastic limestones and oolites.

The spatial and temporal facies pattern indicates transgressions and regressions, which can be linked to the opening of the northern Atlantic. Palaeogeographically the uplift of the eastern hinterland and the Sesimbra diapir are of particular importance.

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R. R. Leinfelder (1983) :

New mapping results on sheet Setubal (Sesimbra to Portinho da Arrábida, Serra da Arrábida, Portugal)

Comun. Serv. Geol. Portugal, 1983, 9, fasc. 2, pp. 295-324

Abstract

In the course of a new geological mapping of the Serra da Arrábida (Estremadura, Portugal) considerable differences compared to the existing official map occurred between Sesimbra and Portinho da Arrábida. By means of microfacial and faunistic-stratigraphic investigations, larger areas are considered to be of Middle Jurassic than previously thought.

From the Upper Jurassic seven lithological sections were examined. Upper Jurassic sediments have been subdivided into five mappable units. Tectonic analysis also could be further differentiated by the refined methods. The application of new tectonic methods and the new stratigraphic results lead to a more differentiated tectonic interpretation of the area. The new mapping results allow to draw new paleogeographic conclusions.

Resumo

Com a realização de novos levantamentos na Serra da Arrábida foram evidenciadas na região entre Sesimbra e Portinho da Airrábida diferenças significativas relativamente à carta geológica publicada. Com base em estudos paleontológico-estratigráficos e microfácies dataram-se do Jurássico médio afloramentos até aqui não considerados como tal.

Descrevem-se sete cortes do Jurássico superior, o qual foi possível subdividir em cinco unidades cartografáveis, A região foi igualmente objecto de estudo tectónico pormenorizado. Os resultados cartográficos e o estudo das fácies permitiram formular novas conclusões paleogeográficas.


Leinfelder , R.R. (1985):

Cyanophyte calcification morphotypes and depositional environments (Alenquer Oncolite, Upper Kimmeridgian ?, Portugal). -

Facies, 12: 253-274; Erlangen.

Summary

Terrigeneous red siliciclastics of Upper Kimmeridgian(?) to Portlandian age around Alenquer, Portugal, comprise a narrow level of oncoid-bearing limestones. Oncoid cortices are composed of cyanophytes which appear in different calcification morphotypes according to changing physico-chemical parameters. Recent examples reveal that in most cases each calcification morphotype is related to one single species or one defined association. Hence, the characteristic calcification patterns are mostly biologically rather than abiogenetically controlled. Oncoid shapes, sizes and arrangement, on the other hand, are mainly determined by the hydraulic parameter within the depositional environment.

Accompanying biota as well as sedimentological and diagenetic characteristics suggest a combination of paralic, lacustrine, marsh and fluvial environments with salinities ranging from hypersaline to freshwater conditions. This variety of subenvironments was created by a rapid but short-lived transgression into a graben-or half-graben-like subsiding depression along the active fault system of Vila Franca de Xira.

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Leinfelder, R.R. (1987):

Formation and Significance of Black Pebbles from the Ota Limestone (Upper Jurassic, Portugal). -

Facies, 17: 159-170; Erlangen.

KEYWORDS: MICROFACIES - SEDIMENTOLOGY - SUBAERIAL EXPOSURE - BLACK PEBBLES - CARBONATE PLATFORM - UPPER JURASSIC (OTA LIMESTONE) - PORTUGAL

Summary

Black pebbles are a characteristic facies element of the Upper Jurassic Ota carbonate bank (Portugal). They occur both scattered or concentrated in two horizons, the upper of which is very widespread and may serve as a lithostratigraphic correlation level. Blackening is mainly due to plant material. Organic matter infiltrated soft or slightly cemented sediments as well as solution cavity fillings within cemented limestones.

Black pebbles are in part transported and found in narrow alluvial fans, beach conglomerates and lagoonal settings. Others represent parautochthonous relics of hard brecciated black crusts which were reworked during a local transgression.

Subaerial exposure, leading to the blackening and subsequent distribution of black pebbles, is due to local block-fault tectonics. These are related to the Vila Franca fault system, which formed during a pronounced rifting phase in the Lusitanian Basin.

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Reinhold R. Leinfelder (1987):

Multifactorial control of sedimentation patterns in an ocean marginal basin: the Lusitanian Basin (Portugal) during the Kimmeridgian and Tithonian.-

Geologische Rundschau, 76, 599-631, Stuttgart

Abstract

The Mesozoic Lusitanian Basin developed as a part of the North Atlantic rift system. Tectonic rifting activity was rejuvenated during the Upper Jurassic, leading to intensive differentiation of facies development. Kimmeridgian and Lower Tithonian calcareous and siliciclastic sediments represent basinal and slope, shallow marine, and terrestrial environments. The lithostratigraphic arrangement of facies units is demonstrated. Sediment character, distribution and thicknesses are mainly controlled by synsedimentary faulting, with a partial overprint by uprise of salt diapirs. Eustatic sea level fluctuations, exogenic and biogenic factors resulted in additional control on facies development.

Comparing bathymetric development of major basin sections and simplified plotting on a common time scale is a simple tool to unravel the multifactorial control of sedimentation and to test the validity of some biostratigraphic markers.

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Reinhold R. Leinfelder (1988):

A SEDIMENTARY-PROCESS AND SEDIMENT-THICKNESS RELATED STRATIGRAPHIC MODEL FOR THE KIMMERIDGIAN AND TITHONIAN OF THE LUSITANIAN BASIN (PORTUGAL)

2nd International Symposium on Jurassic Stratigraphy, Lisbon 1987, Proceedings, pp. 933-946.

ABSTRACT

An entirely biostratigraphic classlfication of Kimmeridgian and Tithonian sediments of the Lusitanlan Basin is up to now not possible due to often unsuitable facies development (e.g.. terrestrial clastics).

Sediments can, however, be correlated in a lithostratigraphic scheme. An important correlation level is represented by the lower part of the calcareous-marly "Pteroceriano'- unit, extendlng over major areas of the basin The maximum extension is considered to represent a rather synchronous event, corresponding to rapid spreading of limestone facies in the course of a diachronous transgression, once terrigenous contamination remains under a critical lower value .

Further lithological correlation is possible by comparing bathymetric patterns of major sections. Degree of synchroneity for those events can be approximately found out by means of "reverse" geohistory methods, based on three, partly ammonite-proven para-authochthonous marker levels and averaged depositional rates as calculated from sediment thicknesses. A chronostratigraphic model derived from this method may serve as an additional base for more refined, basinwide paleogeographic reconstructions.

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Reinhold R. Leinfelder (1992):

A Modern-Type Kimmeridgian Reef (Ota Limestone, Portugal):
Implications for Jurassic Reef Models

FACIES, 26, 11- 34, ERLANGEN

KEYWORDS: CORAL REEFS - MICROBIAL CRUSTS - SEDIMENT BALANCE PALAEO-OCEANOGRAPHY - REEF MODELS - PORTUGAL - UPPER JURASSIC (KIMMERIDGIAN)

SUMMARY

Upper Jurassic reefs rich in microbial crusts generally appear in deeper (sponge - 'algal' crust reefs) or in very shallow but protected settings (coral or coral-coralline sponge meadows with 'algal' crusts). UpperJurassic high energy reefs (coral reefs and coral-stromatoporoid reefs) normally lack major participation of microbial crusts but rather represent huge bioclastic piles with only minor framestone patches preserved.

An exception to this rule is represented by the high energy, coral-'algal' Ota Reef from the Kimmeridgian of the Lusitanian Basin (Portugal) . The narrow Ota Reef tract rims a small intra-basinal carbonate platform exhibiting perfect facies zonation (from W to E: Reef tract, back reef sands, peritidal belt, low-energy shallow lagoon) . The reef is dominated by massive corals (Thamnasteria, Microsolena, Stylina). Complete preservation of coral framework is rare: like other Upper Jurassic high-energy reefs, the Ota Reef is very rich in debris; however, this debris is largely stabilized by algal and microbial crusts, what contrasts the other examples and gives the Ota Reef the appearance of a typical modem high-energy coral-melobesioid algal reef. Further similarities to modern reefs are the likely existence of a spur-and-groove system, the perfect sheltering of inner platform areas and the occurrence of small islands, as indicated by local blackenings and early vadose and karstic features.

The exceptional character of the Ota Reef is thought to be due to the establishment of an equilibrated sediment balance. In a modern high-energy reef, physical and bio logical genereration of debris is compensated by
(1) stabilization of loose debris by binding organisms, chiefly melobesioid algae,
(2) accelerated coral-growth in order to keep pace with sedimentation, and
(3) export of surplus material into back reef and fore reef areas through wave action. Since during the Late Jurassic, fast growing corals were rare and only less effective microbial binders were available, sediment balance could normally not be achieved in a comparable high-energy setting. This resulted in the increasing loss of stable bottom due to sedimentation and eventual suffocation of reef patches. However, in the Ota example the existence of a steep by-pass margin accounted for equilibrated sediment balance:
(1) along the steep margin additional gravitational export was possible;
(2) the steepness of the margin kept the reef tract narrow, so that it could be well winnowed by a longshore current system along the east side of the basin;
(3) the remaining loose debris could, to a large extent, be stabilized by the available algal-like and microbial binders (thrombolitic-peloidal crusts, Bacinella, Lithocodium, Thaumatoporella, Tubiphytes).

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P. M. Ellis*, R. C. L. WILSON* and R. R. LEINFELDER~ (1990)

Controls on Upper Jurassic carbonate buildup development in the Lusitanian Basin, Portugal

Spec. Publs int. Ass. Sediment. (1990) 9,169Ñ202

*Department of Earth Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK; and
Institut fur Geowissenschaften, Universitat Mainz, Saarstrasse 21, D-6500 Mainz, West Germany (presently Stuttgart)

ABSTRACT

A variety of carbonate buildups developed in the Lusitanian Basin during the late Jurassic. During an Oxfordian-Kimmeridgian rift phase evidence can be seen for both fault and diapiric control of buildup development. Fault-controlled buildups occur on the east side of the basin. They exhibit shelf profiles, are relatively thin (200-500m), show well-developed lateral facies zonation and are dominated by lime mudstones and wackestones, with only minor amounts of packstones and grainstones. Salt-controlled buildups on the northwest margin of the basin are relatively thick (500Ñ1500m), show only gradual lateral facies variation with no distinct shelf break facies, and are dominated by grainstones and packstones. During the latest Oxfordian-early Kimmeridgian, a sudden relative sea-level rise drowned or partially drowned the earlier buildups, and this was quickly followed by a major influx of siliciclastic sediments. In the centre of the basin, a thin grainstone-dominated carbonate sequence of middle Kimmeridgian age developed on top of a prograding siliciclastic slope system. In the siliciclastic-starved southern part of the basin, a prograding low-energy ramp sequence of Kimmeridgian-Berriasian age was deposited. Carbonate facies associations described from Portugal also occur in Mesozoic carbonate bank sequences of eastern America. Data from recent US wells, and comparisons with Portugal, suggest that the eastern American Atlantic 'reef trend' is largely composed of grainstoneÑpackstone dominated shelf-break sediments with only relatively minor amounts of biogenic reefal framework.

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Leinfelder R.R. & Wilson, R.C.L. (1989):

Seismic and sedimentologic features of Oxfordian - Kimmeridgian syn-rift sediments on the eastern margin of the Lusitanian Basin. -

Geol. Rdsch., 78: 81-104; Stuttgart.

Abstract

Following deposition of widespread middle Oxfordian lacustrine carbonates and evaporites, the Lusitanian Basin was differentiated into a number of sub-basins. The Arruda sub-basin is a half graben basin situated some 30 km north of Lisbon. It accumulated over 2.5 km of Kimmeridgian siliciclastic sediments, and is bounded to the east by the Vila Franca de Xira fault zone. Carbonate deposition persisted over horsts along the fault zone from the Oxfordian to the early Kimmerdgian, and in places to the late Kimmeridgian, and shows a pronounced west-east facies zonation, with higher energy framestones and grainstones accumulating along the exposed western margins. Seismic data indicate a major gap between the hors blocks that acted as a conduit through which basement derived siliciclastics were fed westwards into the sub-basin to form a submarine fan system. The presence of large blocks of framestone carbonates encased in siliciclastics indicates that carbonate sedimentation occurred in abandoned parts of the fan system. The rapid changes of sediment thicknesses and facies types along the eastern margin of the Arruda sub-basin are indicative of contemporaneous strike-slip movements.

Resumo

Depois da sedimentação dos calcários lacustres e depósitos evaporíticos da idade Oxfordiano médio, a Bacia Lusitánica diferenciou-se em várias sub-bacias. A sub-bacia de Arruda está situada ca. de 30 km ao norte de Lisboa e corresponde a uma estrutura "half-graben" em que mais do que 2.5 km de sedimentos foram acumulados. Para leste, a sub-bacia é limitada pela zona das falhas de Vila Franca de Xira. Entre o Oxfordiano e o Kimeridgiano, calcários desenvolveram-se em cima dos blocos elevados ("horsts") ao longo da zona de falhas. Estes calcários de tipo plataforma exibem uma distincta zonação de facies de oeste a leste. As margens occidentais das plataformas pequenas são caracterisadas por sedi mentos recifais e areníticos. Cortes sísmicos indicam uma abertura grande entre os blocos elevados, pelo qual sedimentos siliciclásticos passaram de "hinterland" à sub-bacia for mando um "fan" submarino. Grandes blocos recifais situa dos dentro dos depósitos siliciclásticos são evidências para sedimentação carbonática em várias áreas abandonadas dentro do "fan". Mudanças rápidas das espessuras e das fácies dos sedimentos ao longo da margem oriental da sub-bacia de Arruda podiam ser explicadas por uma tectónica sinsedimentária dominada por movimentos horizontais.

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Last changes 2. November 1995/21.Nov. 2004 by Reinhold Leinfelder