Ultrastructure, dissolution and "pyritization" of Late Quaternary and Recent echinoderms

The diagenetic history of the skeletal elements of Late Pleistocene-Holocene Ophiura sarsi from the shelf off northern Norway (Andfjorden, Malangsdjupet) is elucidated by comparison with natural and induced degradation of the skeletal elements of Recent ophiuroids (brittle stars) and asteroids (sea stars) from Danish waters. Dissolution features ("core-and-rind") in the trabeculae of fossil and Recent echinoderm stereom are initiated during death and early decay of organic tissue in the animals. The trabeculae have a polycrystalline lamellar ultrastructure and lose their older central part during later stages of dissolution, which are dependant on undersaturation of the sea-water with regard to CaC03• The presence of undersaturated sea-water is supported by palaeoecological studies (Thomsen & Vorren 1984, 1986) implying oxygen deficient periods in the Late Pleistocene and an increased biogenic production in the Holocene. Pyrite framboids are situated in the secondary voids within the trabeculae and in the pore space of the stereom of the Late Pleistocene elements. No pyrite is observed within the polycrystalline lamellar ultrastructure of the trabeculae. The Late Pleistocene "pyritization" took place during oxygen deficient periods at the sediment-water interface or within the reduced zone of the topmost sediment.

Download Full-text

Paleoclimatic and diagenetic history of the late quaternary sediments in a core from the Southeastern Arabian Sea: Geochemical and magnetic signals

Journal of Oceanography ◽

10.1007/s10872-010-0011-2 ◽

2010 ◽

Vol 66 (1) ◽

pp. 133-146 ◽

Cited By ~ 18

Author(s):

Venigalla Purnachandra Rao ◽

Pratima Mohan Kessarkar ◽

Meloth Thamban ◽

Shiva Kumar Patil

Keyword(s):

Arabian Sea ◽

Late Quaternary ◽

Quaternary Sediments ◽

Southeastern Arabian Sea ◽

History Of ◽

Diagenetic History

Download Full-text

Late Quaternary Climate and Vegetation of the Sudanian Zone of Northeast Nigeria

Quaternary Research ◽

10.1006/qres.2002.2356 ◽

2002 ◽

Vol 58 (1) ◽

pp. 73-83 ◽

Cited By ~ 87

Author(s):

Ulrich Salzmann ◽

Philipp Hoelzmann ◽

Irena Morczinek

Keyword(s):

Environmental History ◽

Late Pleistocene ◽

Late Quaternary ◽

Climatic Conditions ◽

Lake Levels ◽

The Holocene ◽

Quaternary Climate ◽

History Of ◽

Sudanian Zone ◽

Humid Period

AbstractThe Lake Tilla crater lake in northeastern Nigeria (10°23′N, 12°08′E) provides a ca. 17,000 14C yr multiproxy record of the environmental history of a Sudanian savanna in West Africa. Evaluation of pollen, diatoms, and sedimentary geochemistry from cores suggests that dry climatic conditions prevailed throughout the late Pleistocene. Before the onset of the Holocene, the slow rise in lake levels was interrupted by a distinct dry event between ca. 10,900 and 10,500 14C yr B.P., which may coincide with the Younger Dryas episode. The onset of the Holocene is marked by an abrupt increase in lake levels and a subsequent spread of Guinean and Sudanian tree taxa into the open grass savanna that predominated throughout the Late Pleistocene. The dominance of the mountain olive Olea hochstetteri suggests cool climatic conditions prior to ca. 8600 14C yr B.P. The early to mid-Holocene humid period culminated between ca. 8500 and 7000 14C yr B.P. with the establishment of a dense Guinean savanna during high lake levels. Frequent fires were important in promoting the open character of the vegetation. The palynological and palaeolimnological data demonstrate that the humid period terminated after ca. 7000 14C yr B.P. in a gradual decline of the precipitation/evaporation ratio and was not interrupted by abrupt climatic events. The aridification trend intensified after ca. 3800 14C yr B.P. and continued until the present.

Download Full-text

Late Quaternary glacial and climate history of the Pamir Mountains derived from cosmogenic 10Be exposure ages

Quaternary Research ◽

10.1016/j.yqres.2005.06.002 ◽

2005 ◽

Vol 64 (2) ◽

pp. 212-220 ◽

Cited By ~ 74

Author(s):

Roland Zech ◽

Uwe Abramowski ◽

Bruno Glaser ◽

Pjotr Sosin ◽

Peter W. Kubik ◽

...

Keyword(s):

Late Pleistocene ◽

Late Quaternary ◽

Limited Extent ◽

Climate History ◽

Pamir Mountains ◽

History Of ◽

Cosmogenic 10Be ◽

Exposure Ages ◽

Glacial Advance

AbstractMoraines southwest of Lake Yashilkul, Pamir, Tajikistan, were dated using 10Be exposure ages of boulder surfaces. We found evidence for (1) an extensive glaciation ∼60,000 yr ago; (2) a less extensive glacial advance, which deposited a characteristic hummocky moraine lobe with exposure ages ranging from ∼11,000 to 47,000 yr, probably deposited at or before 47,000 yr ago; and (3) lateral moraines with exposure ages of ∼40,000 yr, 27,000 yr and 19,000 yr, respectively. Increasing aridity in the Pamir is most likely responsible for the progressively limited extent of the glaciers during the Late Pleistocene.

Download Full-text

NEW INSIGHT ABOUT THE DIAGENETIC HISTORY OF MID-PERMIAN SHANXI GROUP SANDSTONE IN THE NORTH CHINA BAISN - EVIDENCE FROM THE PORE SPACE EVOLUTION

10.1130/abs/2018am-315305 ◽

2018 ◽

Author(s):

Zhiyuan Wu ◽

◽

Eric Law ◽

Shangxian Yin ◽

Lihong Ma ◽

...

Keyword(s):

North China ◽

Pore Space ◽

The North ◽

History Of ◽

Diagenetic History

Download Full-text

Late Quaternary lacustrine and deltaic sedimentation near Banff, Alberta

Canadian Journal of Earth Sciences ◽

10.1139/e83-174 ◽

1983 ◽

Vol 20 (12) ◽

pp. 1834-1842 ◽

Cited By ~ 6

Author(s):

R. A. Kostaschuk ◽

D. G. Smith

Keyword(s):

Surface Morphology ◽

Late Pleistocene ◽

Final Stage ◽

Late Quaternary ◽

Low Energy ◽

The West ◽

Deltaic Sedimentation ◽

History Of ◽

Organic Clay ◽

Quaternary History

Evidence provided by surface morphology, exposures, cores, and the stratigraphic positions of Mazama (6600 years BP) and Bridge River (2500 years BP) ashes was used to interpret the origin and late Quaternary history of lacustrine and deltaic sediments in the Bow River valley near Banff, Alberta.There were three distinct stages of Lake Vermilion occupying the study area from Late Pleistocene to mid-Holocene times. The earliest stage was ice dammed, deposited beach gravel and nearshore sand, and drained along the present course of the Cascade River to the east. The second, proglacial stage is associated with thick subsurface deposits of non-organic clay and drained to the east along the course of the modern Bow River. The final stage is suggested by point bar and aeolian beach dune sediments.With the stabilization of the final stage of Lake Vermilion the low-energy, river-dominated Bow Delta prograded into the lake from the west. Progradation of the delta through three depositional zones produced the present Vermilion Lakes.

Download Full-text