Occurrence and geochemistry of lake-bottom manganiferous deposits in Canadian lakes

It is the purpose of this paper to record information concerning the distribution and occurrence of manganiferous concretions and other manganese oxide deposits that develop on certain lake bottoms. During the summer of 1935 several days were devoted to a study of this type of lake bottom deposit in various parts of Nova Scotia. Lake studies in Ontario have extended the known distribution from lakes on or near the Atlantic coast to lakes in southern Ontario. During the writer's first work on lacustrine manganiferous deposits the concretions of manganese oxide which were found were almost entirely limited to the relatively shallow parts of the lakes examined. Other lakes are now known where the manganese oxide appears to occur only in the maximum depths.

(Table 1) Thermoluminescence datings of glacial deposits from several sites in Schleswig-Holstein, north Germany

First thermoluminescence (TL) datings of glacial deposits from several well-known sites in northwest Germany (Schleswig-Holstein) indicate a possible Middle Weichselian Glaciation in this region. The TL dates obtained imply an ice sheet at about 70-40 ka B.P. here, whose presence in this part of Europe has not been previously considered. The reliability of the TL dates was cross-checked on different lithologies; the dating was performed in two independent laboratories. These dates and their interpretations, however, must still be confirmed both geologically and paleontologically on suitable sites where glacial sediments are sandwiched between Eemian deposits and interstadial deposits older than the Late Weichselian.

Iridium contents and microprobe analyses of DSDP Leg 77 samples

Restudy of Deep Sea Drilling Project Sites 536 and 540 in the southeast Gulf of Mexico gives evidence for a giant wave at Cretaceous-Tertiary boundary time. Five units are recognized: (1) Cenomanian limestone underlies a hiatus in which the five highest Cretaceous stages are missing, possibly because of catastrophic K-T erosion. (2) Pebbly mudstone, 45 m thick, represents a submarine landslide possibly of K-T age. (3) Current-bedded sandstone, more than 2.5 m thick, contains anomalous iridium, tektite glass, and shocked quartz; it is interpreted as ejecta from a nearby impact crater, reworked on the deep-sea floor by the resulting tsunami. (4) A 50-cm interval of calcareous mudstone containing small Cretaceous planktic foraminifera and the Ir peak is interpreted as the silt-size fraction of the Cretaceous material suspended by the impact-generated wave. (5) Calcareous mudstone with basal Tertiary forams and the uppermost tail of the Ir anomaly overlies the disturbed interval, dating the impact and wave event as K-T boundary age. Like Beloc in Haiti and Mimbral in Mexico, Sites 536 and 540 are consistent with a large K-T age impact at the nearby Chicxulub crater.