Upper Jurassic±Lower Cretaceous sponge biostromes and baf¯estone mounds were common and widespread in European temperate to tropical marine environments. They declined markedly during the Late Cretaceous. Most sponge frameworks were paucispeci®c and ecologically simple, with only basic levels of succession or tiering. The occurrence of ecologically complex, lithistid sponge biostromes and mounds in the Cenomanian Quadersandstein Member, Regensburger Gru Ènsandstein of the Saal Quarry, Bavaria, is therefore of special signi®cance. These are ecologically the most complex sponge frameworks yet reported from the Cretaceous. Their size, morphology and ecological organization compare favorably with shallow-water, sponge-dominated frameworks in modern seas. The Saal Quarry sponge frameworks are generally associated with ®rmgrounds and condensed intervals in the transgressive systems tract of the Cenomanian±Turonian, tectonoeustatic supercycle UZA-2. The lowest sponge frameworks are up to 1 m high baf¯estone mounds consisting of large, irregular, sheet-and mound-like recumbent sponges overlain by diverse, cylindrical, pyriform, upwardbranching forms of Jerea and Siphonia. These biostromes overlie a condensed interval or ®rmground which locally contains small, in situ pyriform sponges (Jerea pyriformis Lamouroux) as well as Middle Cenomanian Inoceramus etheridgei Woods. The upper sponge frameworks consist of baf¯estone mounds up to 4.4 m wide and 1.3 m high, composed of six lithistid sponge morphotypes, possibly representing several species of Jerea and Siphonia. The occurrence of Rotalipora cushmanni in strata overlying the upper sponge framework indicates a Late Cenomanian age. Morphotypes preserve internal sponge morphologies and partially dissolved spicules surrounded by a diagenetic halo of silici®ed, pelletoid grainstone and/or packstone. Silica cements were derived from spicule dissolution. Different combinations of these morphotypes dominate three to four successional stages of sponge framework growth, and show vertical ecological tiering within communities. This ecological zonation is consistent among frameworks, and is partially or wholly repeated between storm-related disturbance events.

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In an area regarded to be very favorable for the study of Holocene sea level changes one or several eustatic (?) oscillations of sea have been found using sedimentological and ecological methods. After a maximum of +3 m during the Nouakchottian stage (= Middle Flandrian or Late Atlantic) about 5500 YBP a drop of sea to −3.5 ± 0.5 m about 4100 YBP is testified by stromatolitic algae indicating the former sea level within the tidal zone with high accuracy. This evidence is supported by the observation of post-Nouakchottian regressive and transgressive geologic sequences, by buried beach deposits and flooded hardgrounds, post-Nouakchottian marine terraces of different height and age, the cutting off of one large and several small bays from the open sea, etc. Possibly one or two smaller oscillations followed between 4000 and 1500 YBP (derived sea level curve Fig. 3).

A new occurrence of Recent stromatolites different from those known up to now has been discovered on tidal flats of the Bay of Saint‐Jean (near Cape Timiris). Their most remarkable features are predominance of quartz sand instead of carbonate, characteristic surface‐contouring by grazing fish, absence of cementation, intensive reworking by crabs, and connection with saline sabkha deposits. Entrapment of sand grains and great resistance of the algal sheaths are most important for stromatolitic growth, although today destruction appears to prevail over accretion. Quartz sand of aeolian dunes and carbonatic pellets of aragonitic ooze feeders are the main constituents of the stromatolitic sediments. According to the tidal range the following zonation of the algal mat exists: (A) knoll and cuspate zone, (B) flat zone, (C) gas‐domed zone, and (D) crinkle zone.

ZusammenfassungIn den vorherrschend vulkanischen Serien des Neokoms im westlichen Tell der andinen Geosynldinale Mittelchiles kam es nur untergeordnet zur Ausbildung kalldger Sedimente. Die bedeutenden Faziesunterschiede dieser Flachwassersedimente lassen sich durch ein intensives, durch unregelmiil3ige LavastrSme erzeugtes Kleinrelief erklaren. Der, die BiozSnosen bestimmende 5kologische Hanptfaktor war die Sauerstoffversorgung. BiozSnosen des ,,Hyperpneustons" (Brandungszonen anf Lavarficken), umgeben yon grobem Schalenschutt, lagen dicht neben euxinischen, lebensfeindlichen Schlammzonen (,,Apneuston"). Die Kalkbildung beruhte weitgehend auf Schalendetritus. Anzeichen einer anorganogenen Kalkf~llung fehlen im Hauptgebiet des Vulkanismus. Westlich Santiago bfldeten die Ausbmchszentren geschlossene Inselbarrieren mit nur kleinen Meeresbuchten, in denen jedoch der Anteil planktonischer Organismen bemerkenswert ist. Nach Norden zu, mit zuriicktretendem Vulkanismus, herrschten grSBere zusammenhiingende Meeresbecken mit zunehmend besseren Lebensbedingungen vor. AbstractThe carbonatic sediments are poorly developed in the predominant volcanic series of the Neocomian Age in the western part of the Andean Geosyncline. The significant facies-differentiations of these shallow water sediments can be explained by an intensive fine-relief formed by irregular lava-flows. The supply of oxygen was the main factor involved in the distribution of life associations. Communities of a "byperpneuston" (a zone of strong water agitation on the crests of lavaflows) surrounded by coarse fossil debris, joined euxinic, abiotic muddy-bottom zones. The formation of carbonatic sediments is mainly based on detritical shelldebris. In the main region of volcanism the anorganic precipitation of carbonatic sediments is lacking.West of Santiago the centers of eruptions formed closed bmTiers of islands, in which the sea formed small bays containing an astonishing amount of planktonic organisms. Towards the north more extensive marine basins domi= nated with better conditions for life, because the volcanism diminished.