(Figure 2) Stratigraphic distribution of Schizosphaerella in DSDP Hole 79-547B

• Main Authors: Kälin, Otto, Bernoulli, Daniel
• Format: Dataset
• Language: English
• Published: PANGAEA 1984
• Subjects: 79-547B; Deep Sea Drilling Project; DRILL; Drilling/drill rig; DSDP; DSDP/ODP/IODP sample designation; Glomar Challenger; Leg79; Light microscope; Method comment; North Atlantic/PLATEAU; Sample code/label; Scanning electron microscope (SEM); Schizosphaerella astraea; Schizosphaerella punctulata; Schizosphaerella spp; North Atlantic
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.809380; https://doi.org/10.1594/PANGAEA.809380

The Jurassic (hemi)pelagic continental margin deposits drilled at Hole 547B, off the Moroccan coast, reveal striking Tethyan affinity. Analogies concern not only types and gross vertical evolution of facies, but also composition and textures of the fine sediment and the pattern of diagenetic alteration. In this context, the occurrence of the nanno-organism Schizosphaerella Deflandre and Dangeard (sometimes as a conspicuous portion of the fine-grained carbonate fraction) is of particular interest. Schizosphaerella, an incertae sedis taxon, has been widely recorded as a sediment contributor from Tethyan Jurassic deeper-water carbonate facies exposed on land. Because of its extremely long range (Hettangian to early Kimmeridgian), the genus Schizosphaerella (two species currently described, S. punctulata Deflandre and Dangeard and S. astrea Moshkovitz) is obviously not of great biostratigraphic interest. However, it is of interest in sedimentology and petrology. Specifically, Schizosphaerella was often the only component of the initial fine-grained fraction of a sediment that was able to resist diagenetic obliteration. However, alteration of the original skeletal structure did occur to various degrees. Crystal habit and mineralogy of the fundamental skeletal elements, as well as their mode of mutual arrangement in the test wall with the implied high initial porosity of the skeleton (60-70%), appear to be responsible for this outstanding resistance. Moreover, the ability to concentrate within and, in the case of the species S. punctulata, around the skeleton, large amounts of diagenetic calcite also contributed to the resistance. In both species of Schizosphaerella, occlusion of the original skeletal void space during diagenesis appears to have proceeded in an analogous manner, with an initial slight uniform syntaxial enlargement of the basic lamellar skeletal crystallites followed, upon mutual impingement, by uneven accretion of overgrowth cement in the remaining skeletal voids. However, distinctive fabrics are ...