Bioturbation structures preserved in the c. 260 m long Toarcian section of the Llanbedr (Mochras Farm) borehole (Wales, UK) display cyclic occurrences influenced by astronomical forcing. Depth-domain data series of ichnotaxa distribution were analysed using recurrence plots, which allow observation of cyclic patterns across various scales simultaneously and assessment of the varied responses of different tracemakers to the influence of particular orbital terms. Phycosiphon and Schaubcylindrichnus occurrences reflect the combined effect of precession, obliquity, and short eccentricity. In turn, conditions favouring the development of undulated bedding and the Thalassinoides and Trichichnus tracemakers were primarily controlled by the long eccentricity. Disruptions in the plots likely result from average sedimentation rate changes, and stress conditions experienced by benthic fauna during the latter stages of the Early Toarcian carbon isotope excursion. Generally, the plots reveal patterns characteristic of systems governed by deterministic chaos, with pronounced cyclic components.
The siliciclastic Bajocian–Bathonian Pelion Formation of Tværdal, Geographical Society Ø, East Greenland, is dominated by shallow-marine sandstones, which yielded 22 bivalve taxa representing 18 genera; these are described and figured here. The type species of the subgenus Strimodiolus, Modiolus (Strimodiolus) elongatus Fürsich, 1982, is a junior homonym of Modiola elongata Swainson, 1821 and is replaced by M. (Modiolus) milnelandensis nom. nov. Infaunal taxa dominate in terms of abundance and species richness, and several of the semi-infaunal (e.g., Strimodiolus, Cyrtopinna) and deep-burrowing (Pleuromya) bivalves are preserved in life position, suggesting periodical high sedimentation rates below the fair-weather wave-base during deposition of most of the formation
The finding of two new specimens and a reappraisal of the single original specimen of the problematic giant Canadian Late Jurassic ammonite Titanites occidentalis Frebold results in the creation of Corbinites, n. gen. It is assigned to the ataxioceratid subfamily Lithacoceratinae largely because of the presence of variocostate and previously unrecognized ataxioceratoid ribbing in middle and late growth stages. With enigmatic ancestry and geographically removed other forms with similar characteristics, the species may have been endemic in the relatively isolated early Alberta foreland basin of western interior Canada.
The Late Jurassic shallow-water carbonates with intervening clayey-marly deeper-water deposits in the Holy Cross Mts. area formed over large bank of the elevated part of the Northern Tethyan Shelf during about 12 myr. They comprise three main successions (I, II and III) deposited partly in different environmental conditions, controlled by tectonic and climatic factors, and still preserved in the north-eastern margin, the north-western margin and the south-western margin of the Holy Cross Mountains. The history of sedimentation is presented according to the concept of the large tectono-stratigraphic units COK, LUK and KVB, which owe their origin to variable rates of tectonic subsidence, as introduced by Kutek (1994) for the area of central Poland. The studied deposits of the COK megasequence corresponding to the Upper Oxfordian and the Lower Kimmeridgian up to the Hypselocyclum Zone consist of coral limestones, various grained (including oolitic) limestones, and micritic limestones formed over the gradually enlarging shallow-water carbonate platform of the Holy Cross Mts. This platform was subsequently subdivided into two elevated areas, separated by a depressed zone in the middle, bounded by the Nowe Miasto–Iłża–Bałtów Fault Zone in the north-east and the Holy Cross Fault System in the south. The younger megasequence LUK with it strongly transgressive character marks the successive stages of the marine transgression which entered the central, lowered part of the area of the Holy Cross Mts. from the west, where it appeared already in the early Hypselocyclum Chron. It successively spread across the Holy Cross Mts. area towards the north-east and south bringing everywhere the deposition of various oyster lumachelles and marls with ammonites at the end of the Hypselocyclum Chron and during the Divisum Chron of the Early Kimmeridgian to the Acanthicum/Mutabilis Chron of the earliest Late Kimmeridgian. The following megasequence KVB is represented by the detrital lumachelles and chalky limestones with nereineids of the Eudoxus Chron of the Late Kimmeridgian marking the development of still younger shallow-water carbonate platform in the uplifted areas in the north-eastern and possibly the south-western margins of the mountains, allegedly subdivided by a deeper area of sedimentation of marly deposits. The youngest Late Jurassic deposits of the Holy Cross Mts., are very fragmentarily preserved, mostly because of Early Cretaceous uplift and erosion. They suggest an initial episode of complete drowning of the carbonate platform which became covered by marly deposits during the Early Tithonian, and the subsequent restoration of shallow-water carbonate sedimentation at the end of the Early Tithonian.
The study of the Tithonian and lower Berriasian succession of Le Saix (Hautes-Alpes, France) has made it possible to better characterize the lithological succession at a former Berriasian GSSP candidate, its set of microfacies, the stratigraphic ranges of the main groups of marine plankton and therefore the calpionellid and saccocomid biozonations. On the lithological level, the Tithonian strata are characterized by thick-bedded breccias representing debris flows and related calciturbidites, whereas the Berriasian strata are typically white limestones. The lower part of the Berriasian is comprised of scattered intercalations of thin-bedded breccias and calciturbitides (including cryptic mud calciturbidites). In thin sections, the white limestones display mud- to wackestone textures and their allochems are mostly tiny bioclasts (e.g., radiolarians, calpionellids, saccocomids). Calciturbidites have wacke- to grainstone textures and their allochems are mostly pseudointraclasts and extraclasts, comprising various bioclasts and some ooids. Mud turbidites are made of micrograinstones some yielding almost exclusively well-sorted calpionellids, which were previously erroneously interpreted as the signature of “explosions” or “blooms” of Calpionella alpina. Breccias are mostly lithoclastic floatstones with a matrix similar to that of the calciturbidites. Their lithoclasts are either extraclasts sensu stricto, i.e., material derived from updip shallow-water areas, or pseudointraclasts representing reworked subautochthonous material, i.e., mud- and wackestone lithoclasts with radiolarians, saccocomids and/or calpionellids. Radiolarians are common over the whole studied interval. Saccocomids are part of the dominating biota reported from the lower and lower upper Tithonian interval whereas calpionellids replace them in the uppermost Tithonian to lower Berriasian interval. Minor planktonic groups comprise calcareous dinoflagellates and Globochaete alpina; Iranopsis nov. group is also present. Intervals with saccocomid sections characteristic of zones 4–5 and zone 6 are respectively ascribed here to the lower Tithonian (4–5) and the lower upper Tithonian (6). The biozonation of the calpionellid group sensu lato allows identification of i) the Boneti Subzone of the chitinoidellids, ii) the Crassicollaria Zone, more specifically its Tintinnopsella-Intermedia (A1), Intermedia-Alpina (A2) and Brevis-Massutiniana (A3) subzones, and iii) the Alpina Zone, with its Alpina-Parvula (B1) and its Alpina-Remaniella (B2) subzones. On the basis of biostratigraphical and sedimentological data, most zonal boundaries prove to be hiatal, located at the erosional base of breccia or turbidite layers whereas the Tithonian/Berriasian stage boundary appears to be located at a strike-slip fault plane in the Tré Maroua section.
