Revision and evaluation of the systematic affinity of the calcitarch genusPithonellabased on exquisitely preserved Turonian material from Tanzania

2013 ◽  
Vol 87 (6) ◽  
pp. 1077-1106 ◽  
Author(s):  
Jens E. Wendler ◽  
Ines Wendler ◽  
Brian T. Huber
Keyword(s):  
Upper Cretaceous ◽  
Isotope Geochemistry ◽  
Stable Carbon Isotope ◽  
Outer Wall ◽  
Surface Pattern ◽  
Chemical Signatures ◽  
Reflected Light ◽  
Prismatic Crystal ◽  
Stable Oxygen ◽  
A New Species

Extraordinarily well-preserved pithonellid microfossils (calcitarchs, “calcispheres”) from the Turonian (upper Cretaceous) of Tanzania reveal previously unknown morphological traits, crystallographic patterns, and chemical signatures, providing new insight to this enigmatic group of microfossils. Using combined transmitted-reflected light microscopy, scanning electron microscope imagery, electron microprobe elemental analysis and stable isotope geochemistry, the present study reveals four new aspects of the genusPithonella, notably, the following. An affinity with cyst-forming organisms, potentially the dinoflagellates, is indicated by the presence of a hatch opening and corresponding operculum. The pristine outer wall architecture consists of thin, smooth shingle-shaped plates with regular rows of slit-shaped pores and an apical sub-angular or circular pore. This primary surface pattern is significantly different from previous descriptions of an outer wall consisting of “parquet-shaped” prismatic crystal rows; this latter surface pattern is formed by secondary overgrowth. The crystallographic pattern of the inner wall is crypto-crystalline. Unaltered pithonellids reveal a calcite chemistry characterized by comparably high Mg-contents, relatively enriched stable carbon isotope values, and stable oxygen values indicating a surface water habitat. Based on these previously unseen traits, the diagnosis of the genusPithonellais emended. A new species,Pithonella diconica, is described from the lower-middle Turonian sediments of Tanzania.

scholarly journals Trinocladus divnae and montiella filipovici: A new species (Dasycladales, green algae) from the Upper Cretaceous of the Mountain Pastrik (Mirdita Zone)

2006 ◽  
pp. 65-87 ◽  
Author(s):  
Rajka Radoicic
Keyword(s):  
Shallow Water ◽  
Upper Cretaceous ◽  
Distal Part ◽  
Supplementary Note ◽  
Variable Size ◽  
Tectonic Processes ◽  
Mirdita Zone ◽  
Bathymetric Changes ◽  
Primary Lateral ◽  
A New Species

Two new dasycladalean species from the Upper Cretaceous of the Mountain Pastrik, Kukes Cretaceous Unit of the Mirdita Zone are described: Trinocladus divnae sp. nov. is characterized by variable size of the thallus, relatively narrow main axis, typical Trinocladus organization of the laterals and thin calcification limited to the distal part of the thallus which includes a swollen part of secondaries and short tertiaries. Often, the internal portion of the whorls (except sometimes the main stem membrane), tends to dissolve and form dissolution cavities filled with cement. Montiella filipovici sp. nov. is characterized by a primary skeleton made of a thin individual sheath around a fertile ampullae, often obliterated by recrystallization. Four to six laterals, each giving one secondary and one fertile ampulla located on the upper side of the relatively thick short primary lateral. Upper Cenomanian limestone with Cisalveolina fraasi and Trinocladus divnae sp. nov. was deposited immediately before the events that resulted in sea level rising. The middle and upper Cenomanian eustatic-tectonic processes had different effects in the Pastrik shallow water areas, depending on the distance from the basinal part of the Unit. Bathymetric changes in a part of the Pastrik sedimentary area were not significant, even negligible. Montiella filipovici is found in the post-fraasi shallow water sequence, assigned to the ?uppermost Cenomanian-lowermost Turonian (= Whiteinella archaeocretacea Zone p. p.; a short stratigraphic gap, in a part of the area, is noted). Shallow water limestone with Turonian taxa, corresponding to the helvetca Zone, occurs a few meters upward. Supplementary note: the species Cylindroporella parva RADOICIC is transferred in the genus Montiella, the species Permocalculus elliotti JOHNSON is transferred in the genus Trinocladus, while the species Trinocladus bellus YU JING is transferred in the genus Belzungia.

Fossil wood from the Upper Cretaceous crater sediments of the Salpeterkop volcano, North West Province, South Africa

2021 ◽  
Author(s):  
M. de Wit ◽  
M. Bamford
Keyword(s):  
South Africa ◽  
Upper Cretaceous ◽  
Ring Structure ◽  
Fossil Wood ◽  
Growth Rings ◽  
Local Climate ◽  
North West ◽  
Igneous Province ◽  
Fossil Genus ◽  
A New Species

Abstract The Salpeterkop volcano forms part of what has been referred to as the Upper Cretaceous Sutherland Suite of alkaline rocks, an igneous province composed of olivine melilitites, carbonatites, trachytes and ultramafic lamprophyres. Salpeterkop is a remnant of the summit tuff ring structure that surrounds a crater which is almost 1 km in diameter and is filled with epiclastic strata. Five pieces of silicified wood were collected from the crater filled sediments, sectioned and identified as a new species of Cupressinoxylon, C. widdringtonioides. This is the first example of the fossil genus in South Africa. Only one member of the Cupressaceae s.l. occurs in southern Africa today. From the wide and indistinct growth rings in the fossil wood it can be deduced that the local climate was warm and humid with little or no seasonality, in support of global records of a warm Late Cretaceous. The preservation of the crater further signifies the low level of erosion the region has experienced since its emplacement.

Definitive data on bohdanowiczite, a new silver bismuth selenide

1979 ◽  
Vol 43 (325) ◽  
pp. 131-133 ◽  
Author(s):  
M. Banaś ◽  
D. Atkin ◽  
J. F. W. Bowles ◽  
P. R. Simpson
Keyword(s):  
Additional Data ◽  
Hexagonal Lattice ◽  
New Mineral ◽  
Calculated Density ◽  
Yellow Colour ◽  
Cell Parameters ◽  
Reflected Light ◽  
Polysynthetic Twinning ◽  
Polymetallic Mineralization ◽  
A New Species

SummaryBohdanowiczite was first described in 1967 but incomplete data prevented its acceptance as a new mineral at that time. Additional data on the same material now characterize bohdanowiczite as a new species with the formula:3[(Ag0.98Cu0.02)0.97(Bi0.97Pb0.03)1.02(Se0.83S0.17)2.01]The mineral occurs in intimate intergrowths with clausthalite and wittichenite in polymetallic mineralization at Kletno in Poland. In reflected light bohdanowiczite has a creamy-yellow colour and short polysynthetic twinning is frequently observed. Cell parameters indexed on a hexagonal lattice are a = 4.183±0.008 Å and c = 19.561± 0.016 Å. Pm1 is the most likely space group. The strongest lines of the powder pattern are 2.91(100), 2.03(30), 3.40(20), 6.54(20), 2.09(18), 3.26(18). The calculated density is 7.72 gm/cm3 and the VHN between 63 and 96 kg/mm2.

Sign in / Sign up

Export Citation Format

Share Document