Late holocene linkages between decade-century scale climate variability and productivity at Lake Tanganyika, Africa

Microlaminated sediment cores from the Kalya slope region of Lake Tanganyika provide a near-annually resolved paleoclimate record between ~~2,840 and 1,420 cal. yr B.P. demonstrating strong linkages between climate variability and lacustrine productivity. Laminae couplets comprise dark, terrigenous-dominated half couplets, interpreted as low density underflows deposited from riverine sources during the rainy season, alternating with light, planktonic diatomaceous ooze, with little terrigenous component, interpreted as windy/dry season deposits. Laminated portions of the studied cores consist of conspicuous dark and light colored bundles of laminae couplets. Light and dark bundles alternate at decadal time scales. Within dark bundles, both light and dark half couplets are significantly thinner than within light bundles, implying slower sediment accumulation rates during both seasons over those intervals. Time series analyses of laminae thickness patterns demonstrate significant periodicities at interannual¿centennial time scales. Longer time scale periodicities (multidecadal to centennial scale) of light and dark half couplet thicknesses are coherent and in some cases are similar to solar cycle periods on these time scales. Although laminae thickness cycles do not strongly covary with the actual ¿14C record for this same time period, two large ¿14C anomalies are associated with substantial decreases in both light and dark laminae thickness. In contrast to the multidecadal¿ centennial time scale, significant annual to decadal periodicities, which are broadly consistent with ENSO/PDO forcing and their impact on East African climate, are not coherent between light and dark half couplets. The coherency of light¿dark couplets at decadal¿centennial time scales, but not at shorter time scales, is consistent with a model of a long-term relationship between precipitation (recorded in wet season dark laminae thickness) and productivity (light laminae thickness), which is not manifest at shorter time scales. We hypothesize that this coupling results from long-term recharging of internal nutrient loading during wet periods (higher erosion of soil P) and reduced loading during drought intervals. The relationship is not expressed on short time scales during which the dominant control on productivity is wind-driven, dry season upwelling, which is uncorrelated with wet-season precipitation. Our record greatly extends the temporal record of this quasi-periodic behavior throughout the late Holocene and provides the first evidence linking decade- to century-scale episodes of enhanced productivity to enhanced precipitation levels and nutrient recharge in a productive tropical lake

Diversity and palaeoecology of Australia's southern‐most sauropods, Griman Creek Formation (Cenomanian), New South Wales, Australia

Predominately, occurances of Australian sauropods from the Early to mid-Cretaceous of Queensland and Western Australia, lie between ~45° and 55°S palaeolatitude. The Cenomanian Griman Creek Formation, which straddles the New South Wales-Queensland border, preserves arguably one of the richest Cretaceous terrestrial faunas in Australia. Although sauropod postcranial elements are notably absent or as yet unidentified, isolated sauropod teeth are relatively well represented from exposures near Lightning Ridge (New South Wales), offering insights into the diversity and palaeoecology of these animals at ~60°S palaeolatitude. From a sample of 25 teeth, we identify five dental morphotypes from the Griman Creek Formation. Some of this variation is attributed to heterodonty; however, other distinctive morphologies partly agree with previous indications of at least two taxa of non-titanosaur titanosauriforms together with a third, possible titanosaur in the Griman Creek Formation. An investigation of dental microwear found two teeth with identifiable wear features, but differences in these features suggest separate feeding strategies consistent with the hypothesis of ecological tiering between sympatric species. The presence of at least two non-titanosaur titanosauriforms and a third species of titanosaur in the Griman Creek Formation is reminiscent of the roughly coeval Winton Formation in central Queensland, which preserves three titanosauriform species, and implies that diverse sauropod communities persisted during this interval into their most southern recorded range in Australia

Asociaciones de quistes de dinoflagelados de agua salobre a dulce de la formacion la colonia (Paleoceno?), Noreste de Patagonia, Argentina

A palynological analysis of the section of La Colonia Formation exposed at Estancia San Miguel yielded conspicuous assemblages of organic-walled dinoflagellate cysts (dinocysts) and green algae. The monotypic palaeoperidinioid dinocyst assemblage of ?Ginginodinium sp. in the basal beds of this section indicates low-salinity water conditions in a restricted shallow marine paleoenvironment. The green-algae-dominated assemblages together with specimens of ?Morkallacysta spp., Dinocysts type P and ?Vesperopsis sp. recorded in the middle and upper part of the San Miguel section indicate brackish to freshwater and freshwater depositional conditions, respectively. The changes in the composition of the palynological assemblages, in agreement with the analysis of the sedimentary facies, reflect a salinity-drop in the water bodies and a progressive upward-shallowing trend. The occurrence of specimens of the neritic open marine Cribroperidinium spp., Apteodinium sp., Circulodinium sp. and Areoligera sp. cf. A. circumsenonensis Fensome et al. is here considered as reflecting contemporaneous transported material from the adjacent shelf. The marine part of the La Colonia Formation is associated to Late Cretaceous and Paleocene ages. Nevertheless, palynomorphs together with a stratigraphical criterion suggest an age non older than Paleocene for the deposits of the unit at the San Miguel section