I was wondering aloud yesterday on one of my lists what surprises Mars may still have in store for us (now that granite and low-latitude glaciers are on the list of goodies). One of the surprises I had in mind was evidence of plate tectonics (PT). It seems it's not that much of a surprise, or at least not a new surprise. This NASA article describes how evidence for PT was discovered as early as 1999 (for those of you who don't already know this!). The evidence is not based on geological structures, but on a magnetic field map, made with the help of magnetometer readings taken by the Mars Global Surveyor spacecraft.

- posted by Affenhänger @ 10/19/2005 06:21:00 PM 0 comments links to this post

The inimitable Carnets de Géologie has announced the publication of a new "article":

Vinn O. (2005).- The distribution of worm borings in brachiopod shells from the Caradoc Oil Shale of Estonia.- Carnets de Géologie - Notebooks on Geology, Brest, Article 2005/03 (CG2005_A03), 11 p., 5 fig., 4 tabl., 2 pl.

Un nouvel "Article" (CG2005 A03) est en ligne depuis le 06.10.2005 :
Vinn O. (2005).- Distribution des perforations de vers dans les coquilles de brachiopodes des schistes bitumineux du Caradoc d'Estonie.- Carnets de Géologie - Notebooks on Geology, Brest, Article 2005/03 (CG2005_A03), 11 p., 5 fig., 4 tabl., 2 pl.
[Ce Mémoire n'est disponible que dans sa version anglaise]

Abstract:
Abundant worm borings were found in some brachiopod shells (Clitambonites, Estlandia, Nicolella) from the Ordovician (Caradoc) oil shale in North Estonia. 9 of 21 brachiopod genera (43%) have been bored. Excluding the size and thickness of valves, no common morphological feature discriminates the brachiopods with borings from those without them. The Trypanites are host-specific, and the frequency of bored valves varies from 6.5% in Bekkerina to 51% in Estlandia. The worm larvae preferred hosts with thick lamellose shells, such as those of the clitambonitids, especially Clitambonites schmidti. The boring organisms were size-selective; they preferred large adult specimens. The majority of the borings are oriented, and living hosts were preferred to dead shells. Some clitambonitidine brachiopods, like C. schmidti tolerated a large number of the borer's shafts in their valves. Few bored valves have the blister-like shell-repair structures in their interior.

Résumé :
Des perforations dues à des vers sont observées en abondance sur les coquilles de quelques brachiopodes (Clitambonites, Estlandia, Nicolella) des schistes bitumineux caradociens du Nord de l'Estonie. Ainsi, 9 des 21 genres de brachiopodes (43 %) étudiés ont des valves perforées. La présence ou l'absence des parforations est liée à taille et l'épaisseur des valves. Les autres traits morphologiques semblent n'avoir aucune importance. Dans l'ensemble, en effet, les larves des vers marquent une préférence pour des coquilles épaisses et lamelleuses, comme celles des clitambonitidés, particulièrement Clitambonites schmidti. On note, cependant que les représentants de l'ichnogenre Trypanites marquent quelques préférences spécifiques, ainsi leur fréquence varie de 6.5 % chez Bekkerina à 51 % chez Estlandia. La majorité des perforations sont orientées et les coquilles d'individus vivants étaient préférées aux coquilles vides. Certains brachiopodes clitambonitidés, comme Clitambonites schmidti, ont toléré un grand nombre de perforations dans leurs valves. Seul un petit nombre de valves trouées ont révélées des cals de réparation de la coquille sur leur face interne.

- posted by Affenhänger @ 10/09/2005 08:12:00 PM 0 comments links to this post

Remains of photosynthesizing microbes in prehistoric rocks suggest Earth was not ice-bound, as long proposed by supporters of the "Snowball Earth" theory.

By Carl Marziali

A study that applied innovative techniques to previously unexamined rock formations has turned up strong evidence on the "Slushball Earth" side of a decades-long scientific argument.

The study appears in the Sept. 29 Science Express. The lead author is Alison Olcott, a Ph.D. student of earth sciences in the USC College of Letters, Arts and Sciences.

Geologists agree that prehistoric Earth was locked in a deep freeze during Precambrian times, about 750 to 600 million years ago. They disagree over the severity of the glaciation.

"Snowball Earth" proponents, who say that Earth’s oceans were covered by thick ice, explain the survival of life by hypothesizing the existence of small warm spots, or refugia.

On the other side are supporters of a "Slushball Earth" that would have included large areas of thin ice or open ocean, particularly around the equator.

The debate has tended to revolve around the same rock samples and analytical techniques, Olcott said. So she and her team focused on a drill core of little-known black shale deposits from southeastern Brazil and applied lipid biomarker techniques to identify prehistoric organisms based on the fatty remains of their cell membranes.

The team, which included scientists from USC, Caltech, the University of Maryland and a Brazilian mining company, identified "a complex and productive microbial ecosystem," including photosynthesizing organisms that could not have existed under a thick layer of ice.

"If there was ice, it had to have been thin enough that organisms could photosynthesize below it or within it," Olcott said.

Frank Corsetti of USC College, one of Olcott’s advisers and a co-author on the paper, said: "What she has provided is the first real evidence that substantial photosynthesis occurred in the Earth’s oceans during the extreme ice age 700 million years ago, which is a challenge for the snowball theory."

The evidence from the drill core does not prove that large parts of the ocean remained free of sheet ice during the pre-Cambrian glaciation. It is statistically unlikely but possible, Olcott said, that the drill core found one of the tiny "refugia" for marine life whose existence is allowed under the "Snowball Earth" hypothesis.

But, she said, "finding the one anomalous spot would be quite unlikely," adding that the drill core came from an extensive formation of rocks with similar characteristics.

"At what point does an enormous refugium become open ocean?" she asked.

Skeptics also may argue that the rocks do not necessarily date to a glacial era, Olcott said. But her team found evidence of glacial activity in the samples, such as dropstones (continental rocks dropped by melting glaciers into marine deposits) and glendonites (minerals that only form in near-freezing water).

Objections aside, the paper’s main contribution may be the application of new techniques to an old chestnut.

"Geologists don’t necessarily think of looking for traces of microbes left in the rocks. This is the first direct look at the ecosystem during this time period," said Olcott, who credited USC’s geobiology program, one of a handful in the country, with influencing her thinking.

"They really try to synthesize between geology and biology. It was a new way to attack the problem."

Corsetti agrees. "The climate of collaboration between geologists and biologists," he said, "is unusually good at USC … it was this way of thinking that provided the impetus for the project in the first place."

Funding for Olcott’s project came from the National Science Foundation and NASA.

This story was orignally released on Spetember 29 by the University of Southern California (USC) and can be read here.

- posted by Affenhänger @ 10/09/2005 06:21:00 PM 0 comments links to this post

2005/10/08 05:26 M 5.6 PAKISTAN Z= 10km 34.71N  73.11E

        This information is provided by the USGS
         National Earthquake Information Center.
    (Address problems to: sedas@ghtmail.cr.usgs.gov)

These parameters are preliminary and subject to revision.

A magnitude 5.6 earthquake IN PAKISTAN has occurred at:
34.71N  73.11E  Depth  10km  Sat Oct  8 05:26:05 2005 UTC

Time: Universal Time         (UTC) Sat Oct  8 05:26:05 2005
      Time Near Epicenter          Sat Oct  8 10:26:05 2005
      Eastern Daylight Time  (EDT) Sat Oct  8 01:26:05 2005
      Central Daylight Time  (CDT) Sat Oct  8 00:26:05 2005
      Mountain Daylight Time (MDT) Fri Oct  7 23:26:05 2005
      Pacific Daylight Time  (PDT) Fri Oct  7 22:26:05 2005
      Alaska Daylight Time   (ADT) Fri Oct  7 21:26:05 2005
      Hawaii Standard Time   (HST) Fri Oct  7 19:26:05 2005

Location with respect to nearby cities:
     70 km (40 miles) E of Mingaora, Pakistan (pop 174,000)
     115 km (70 miles) N of ISLAMABAD, Pakistan (pop 524,000)
     160 km (100 miles) ENE of Peshawar, Pakistan (pop 988,000)
     165 km (105 miles) SE of Chitral, Pakistan

For maps, additional information, and subsequent updates,
please consult:
http://earthquake.usgs.gov/recenteqsww/Quakes/usdyas.htm .

- posted by Affenhänger @ 10/08/2005 04:16:00 AM 0 comments links to this post

"Gimme a Winchester rifle and whole box of shells"

- posted by Affenhänger @ 10/08/2005 12:16:00 AM 0 comments links to this post