Why do calcareous microfossils preferentially occur in tuffaceous sandstones of the Santa Marta formation (James Ross Island, Antarctica)?

Author(s):  
Rafael R. da Silva ◽  
Karlos G.D. Kochhann ◽  
Rodrigo M. Guerra ◽  
Gerson Fauth ◽  
Marcelo de A. Carvalho ◽  
...  
1989 ◽  
Vol 4 ◽  
pp. 99-100 ◽  
Author(s):  
Jean M. Berdan

The described techniques for extraction of microfossils are directed primarily at the extraction of calcareous microfossils from various types of limestone, although the same techniques may beused for some sandstones and shales. The equipment needed is not complicated; the most obvious is a good binocular microscope with a working distance of three or more inches, to allow manipulation of the rock from which the specimens are to be extracted. The magnification required depends on the size of the specimens, but should go up to at least 80x. Other essential tools are a pin vise with a chuck which will hold an ordinary steel sewing needle and a rotary dental machine or other grinding device which will accept a small thin carborundum wheel. The latter is useful for sharpening needles as well as for cutting specimens out of the rock. An additional useful item is a percussive device such as a mechanical engraver fitted with a chuck which will hold an old fashioned steel phonograph needle. This instrument is described in detail by Palmer (this volume, chapter 20). A dish of water and a fine (00000) camel's hairbrush are necessary to move the specimens, once freed, to a slide or other receptacle. A rock trimmer is useful for reducing large blocks of fossiliferous rock into pieces that can be handled under the microscope, although with some collections this can be done with a hammer and cold chisel. Some paleontologists prefer to crush their samples and then pick through the chips to find specimens; however, this technique tends to break spines and frills from highly ornamented forms and is not recommended unless the microfauna is known to consist mostly of smooth species. Most of the equipment mentioned above can be found in catalogs such as that of the Edmund Scientific Co., 101 E. Gloucester Pike, Barrington, N.J. 08007.


2021 ◽  
Vol 17 (2) ◽  
pp. 125-139
Author(s):  
Stephen J. A. Jennings ◽  
Bethan J. Davies ◽  
Daniel Nývlt ◽  
Neil F. Glasser ◽  
Zbyněk Engel ◽  
...  
Keyword(s):  

1987 ◽  
Vol 33 (115) ◽  
pp. 300-310 ◽  
Author(s):  
T.J.H. Chinn ◽  
A. Dillon

Abstract“Whisky Glacier” on James Ross Island, Antarctic Peninsula, comprises anévéand clean ice trunk surrounded by an extensive area of debris-covered ice resembling a rock glacier. The debris-free trunk of the glacier abuts abruptly against the broad, totally debris-covered tongue at a number of concentric zones where debris-laden beds crop out at the surface in a manner similar to the “inner moraine” formations of many polar glaciers.Ice structures and foliation suggest that “Whisky Glacier” is a polythermal glacier which is wet-based under the debris-free zone, and dry-based under the debris-covered zone. It is surmised that the glacier sole crosses the freezing front close to where the basal debris beds are upwarped towards the surface. Here, basal water is confined, and freezes to the under side of the glacier in thick beds of regelation ice which are uplifted to the surface along with the debris-laden beds. Ablation losses effectively cease beneath the blanket of debris covering the tongue.The transition from wet-based to dry-based conditions at the glacier sole is a powerful mechanism for entraining debris into a glacier and, in the case of “Whisky Glacier”, for lifting debris to the surface. It is suggested that this may be a mechanism for forming some polar rock glaciers.


2009 ◽  
Vol 21 (5) ◽  
pp. 501-504 ◽  
Author(s):  
Alberto Luis Cione ◽  
Francisco Medina

AbstractThe oldest record of the hexanchiform sharks from the Southern Hemisphere and the second chondrichthyan report known from Carboniferous to Early Cretaceous beds in Antarctica is given. The material was collected in late Aptian rocks of the Kotick Point Formation outcropping in the western part of James Ross Island, near Antarctic Peninsula. It consists of an isolated tooth assignable to a hexanchiform different from the other described genera. The tooth shows putative plesiomorphic cusp (few cusps, no serrations) and apomorphic root characters (relatively deep, quadrangular). It could be related to a species close to the origin ofHexanchus(unknown in beds older than Cenomanian).


2013 ◽  
Vol 295 ◽  
pp. 53-66 ◽  
Author(s):  
Marcelo de A. Carvalho ◽  
Renato R. Cabral Ramos ◽  
Monika Beatriz Crud ◽  
Luciana Witovisk ◽  
Alexander W.A. Kellner ◽  
...  

2019 ◽  
Vol 124 (1) ◽  
pp. 149-174 ◽  
Author(s):  
Eliza J. Mathia ◽  
Thomas F. T. Rexer ◽  
K. Mark Thomas ◽  
Leon Bowen ◽  
Andrew C. Aplin

2007 ◽  
Vol 67 (1) ◽  
pp. 69-82 ◽  
Author(s):  
Matthew C. Peros ◽  
Eduard G. Reinhardt ◽  
Anthony M. Davis

AbstractLaguna de la Leche, north coastal Cuba, is a shallow (≤ 3 m), oligohaline (∼ 2.0–4.5‰) coastal lake surrounded by mangroves and cattail stands. A 227-cm core was studied using loss-on-ignition, pollen, calcareous microfossils, and plant macrofossils. From ∼6200 to ∼ 4800 cal yr BP, the area was an oligohaline lake. The period from ∼ 4800 to ∼ 4200 cal yr BP saw higher water levels and a freshened system; these changes are indicated by an increase in the regional pollen rain, as well as by the presence of charophyte oogonia and an increase in freshwater gastropods (Hydrobiidae). By ∼ 4000 cal yr BP, an open mesohaline lagoon had formed; an increase in salt-tolerant foraminifers suggests that water level increase was driven by relative sea level rise. The initiation of Laguna de la Leche correlates with a shift to wetter conditions as indicated in pollen records from the southeastern United States (e.g., Lake Tulane). This synchronicity suggests that sea level rise caused middle Holocene environmental change region-wide. Two other cores sampled from mangrove swamps in the vicinity of Laguna de la Leche indicate that a major expansion of mangroves was underway by ∼ 1700 cal yr BP.


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