Shallowing-upward cycles in pelagic troughs (Upper Jurassic, Subbetic, Southern Spain)
Abstract Abundant calcareous tempestites with chert and hummocky cross-stratification (HCS) occur in Upper Jurassic successions (Milanos Formation) of the Subbetic (Betic Cordillera, Southern Spain). These calcareous tempestite beds are calcisiltites and very fine calcarenites with peloids and bioclasts, and have thicknesses between 25 and 75 cm. Beds show symmetrical wave ripple lamination near the top, and are usually capped with wave ripples. According to palaeogeographic reconstructions, these strata were deposited in a subsiding trough in the pelagic domain of the Southern Iberian Continental Margin, which was the northwestern-most border of the Tethys. Calcisiltite and calcarenite beds deposited in this pelagic trough form small-scale to large-scale shallowing-upward cycles. Shallowing-upward cycles with calcareous tempestites in the lower part and oolitic limestone beds in the upper part, have also been recognized in some sectors of the Subbetic pelagic basin. The large-scale cycle occurs in the upper part of the Jarropa Radiolarite Formation, which directly underlies upper Oxfordian, Kimmeridgian and Tithonian strata of the Milanos Formation. Two types of large-scale shallowing-upward cycles have been recognized, according to the presence or absence of thick units of oolitic limestone with large-scale cross-stratification. The water depth during deposition ranged from below, but near, storm wave base at the base of the large-scale cycles to very shallow carbonate platform at the top.
Three-dimensional burrow systems and taphofacies in shallowing-upward parasequences, lower Jurassic carbonate platform (Calcari Grigi, Southern Alps, Italy)
SummaryAnalysis of parasequences of carbonate platform origin from the Calcari Grigi Formation (Rotzo Member, Lower Jurassic) in the Venetian Pre-Alps of Northern Italy reveals intense burrowing affecting warm lagoonal and protected shelf environments of the Trento carbonate platform. The trace fossil pattern suggests a strong biogenic activity by many unknown organisms (episodic surficial bioturbation) and by decapod crustaceans (deep burrowing) during the Sinemurian—Pliensbachian. Burrow networks ofThalassinoides (T. suevicus, type I to IV) andOphiomorpha form three-dimensional systems (3DBS), up to 150 cm in thickness, that reveal well developed taphonomic characteristics. Occasionally, also rare body fossil remains (exuvia) ofPhlyctisoma (Erymidae) are preserved, although it is very difficult to attribute to this decapod crustacean a real tracemaker activity. In a total of 18 shallowing-upward taphosequences, each 2.3–2.6 m in thickness, the lower, subtidal part (BOP: base of parasequence), is invariably characterized by 3DBS. Three parts of a 3DBS are taphonomically relevant: a) the enlargement at bifurcation points (the so-called turning chambers) with related tunnel sections in horizontal networks; b) the distribution of vertical tunnels and their openings, locally associated with biogenic mounds; and c) the infilling with coarse-grained skeletal debris of abandoned burrows (tubular tempestites). Case (a), although well known in the literature, is nevertheless peculiar because of the exceptional diameter (up to 22 cm) and shape of bifurcations ofThalassinoides suevicus. Therefore their taphonomic analysis helps to refine shallowing-upward taphosequences. Case (b) and (c), instead, are exceptional because traces of the activity of decapod crustaceans at the sea-floor are very rare in the geologic record. The 3DBS involve taphofacies that are peculiar of the upper part of the Calcari Grigi across western Venetian Prealps. The analysis of 3DBS in all Lower Jurassic para-sequences will aid sequence stratigraphy and the paleoenvironmental reconstruction of the carbonate platform setting.
Palaeocarpinus (Extinct Betulaceae) from Northwestern China: New Evidence for Paleocene Floristic Continuity between Asia, North America, and Europe
Spiny-bracted fruits of Palaeocarpinus Crane, a genus of Betulaceae previously known only from Europe and North America, have been discovered in the Paleocene of Altai, northwestern China. The fruits are found in association with abundant Corylus-like foliage and staminate catkins containing Corylus-like pollen. Because of problems distinguishing leaves of Corylus from those of extinct betulaceous genera, we place these leaves in the genus Corylites Gardner ex Seward & Holttum. The fruits, staminate catkins, pollen, and leaves from Altai were probably all produced by a single species. Palaeocarpinus orientalis is nearly identical in its morphology to Palaeocarpinus joffrensis from the Paleocene of North America except in the more rounded primary bracts of the associated staminate catkins. The species is less similar to Palaeocarpinus laciniata from the Paleocene of southern England.