5 ms·

Oldest Body of Seawater Found in Giant Crater

21 points by mikehotel 13y ago

mikehotel 13y ago
Editor's summary from the Nature journal: Geologists and oceanographers generally have to rely on indirect evidence from the analysis of solid materials in deep sediment cores when estimating temperature and salinity levels of the ancient oceans. But now a team from the US Geological Survey has identified a body of underground water that is actually a remnant of a past ocean water, a body of Early Cretaceous North Atlantic sea water. Deep drilling at the site of the Chesapeake Bay impact crater has yielded groundwater with an isotope and chemical composition signature that together with model analysis suggests that it was trapped in the sediments before the impact occurred around 35 million years ago. The water may have lain undisturbed for much longer: it has an average salinity of about 70 parts per thousand, twice that of modern sea water, and is probably 100–145 million years old. http://www.nature.com/nature/journal/v503/n7475/full/nature12714.html http://www.nature.com/nature/journal/v503/n7475/full/nature1...
- mtdewcmu 13y ago
  What struck me is the age of the oldest known seawater. That's on the order of 2% of the age of the earth. There are plenty of rocks that are much older. I guess seawater doesn't keep very well.
  - fhars 13y ago
    For one, rocks don't evaporate in the sunlight at our distance from the sun.
    - mtdewcmu 13y ago
      That's true. But rocks erode at a rapid pace in comparison to the age of the earth. Apparently, very little is left for geologists to study from earlier than about 1 billion years ago. And there is a tremendous amount of groundwater deep underground, with some of it trapped by rock formations.
ams6110 13y ago
...the team was able to figure out the rough age of the ancient water Is there significant creation of "new" water on the earth? I suppose water produced in combustion of hydrocarbons would qualify, but seems to me that's tiny compared to the existing amount of water, which is all roughly the same age (ancient) and is just continually cycling between vapor (evaporation) and liquid (clouds/rain) state. This discovery is simply water that has been in isolation for a long time.
- mtdewcmu 13y ago
  True, but once it evaporates, it can no longer be called seawater. I think you may be reading this in the wrong context. It's a geology story, and geologists study things that have been buried in the ground a long time. The value is in having a sample of prehistoric seawater to study, as if it were a rock formation.
- mikehotel 13y ago
  Recent discoveries of isolated water have lead to investigations of new organisms (see http://www.nature.com/news/russian-scientist-defends-lake-vostok-life-claims-1.12578 http://www.nature.com/news/russian-scientist-defends-lake-vo...). This appears to be much older, but perhaps not as well isolated as Lake Vostok since there appears to be a connection with increased groundwater salinity in the area.
mikehotel 13y ago
Looks like my uneditorialized title was edited to remove the "mind blowing discovery" prefix. I thought HN policy was to use the title as published. In any case, thanks for the edit. I would have done it except for my apparent confusion regarding best practices.
jofer 13y ago
The way this article is written is very misleading. This is not in any form or fashion the "oldest body of seawater yet found" nor is it unusual to find ancient trapped seawater. "Connate water" is water trapped in sediments at the time of their deposition. Whether or not connate water is preserved in large quantities depends on the local permeability structure of the sediments and the regional hydrology. However, it's very common for connate water to be preserved more or less indefinitely (particularly in shales). In other words, there's a _lot_ of trapped seawater almost everywhere you look. What's unique about this isn't that there's trapped seawater, and it's certainly not the oldest connate water discovered (nor do the authors of the actual article claim that it is). It's unique because: A) it's direct evidence that the Central Atlantic had a very high salinity even long after it opened. (The authors are using the term "north atlantic" for some strange reason, but this segment is more commonly referred to as the "central atlantic") B) The connate water survived a metorite impact without being highly disturbed.
imahboob 13y ago
I hate it when these blog journalists don't event know how to read scientific papers
imahboob 13y ago
I hate it when these blog journalists don't event know how to read scientific papers
strathmeyer 13y ago
Mirror??
- gt565k 13y ago
  right click => inspect element => set style to "display:none" on the popup and overlay, and you're good to go.

21 points by mikehotel 13y ago

Editor's summary from the Nature journal: Geologists and oceanographers generally have to rely on indirect evidence from the analysis of solid materials in deep sediment cores when estimating temperature and salinity levels of the ancient oceans. But now a team from the US Geological Survey has identified a body of underground water that is actually a remnant of a past ocean water, a body of Early Cretaceous North Atlantic sea water. Deep drilling at the site of the Chesapeake Bay impact crater has yielded groundwater with an isotope and chemical composition signature that together with model analysis suggests that it was trapped in the sediments before the impact occurred around 35 million years ago. The water may have lain undisturbed for much longer: it has an average salinity of about 70 parts per thousand, twice that of modern sea water, and is probably 100–145 million years old. http://www.nature.com/nature/journal/v503/n7475/full/nature12714.html http://www.nature.com/nature/journal/v503/n7475/full/nature1...

mtdewcmu 13y ago
What struck me is the age of the oldest known seawater. That's on the order of 2% of the age of the earth. There are plenty of rocks that are much older. I guess seawater doesn't keep very well.
- fhars 13y ago
  For one, rocks don't evaporate in the sunlight at our distance from the sun.
  - mtdewcmu 13y ago
    That's true. But rocks erode at a rapid pace in comparison to the age of the earth. Apparently, very little is left for geologists to study from earlier than about 1 billion years ago. And there is a tremendous amount of groundwater deep underground, with some of it trapped by rock formations.

ams6110 13y ago

...the team was able to figure out the rough age of the ancient water Is there significant creation of "new" water on the earth? I suppose water produced in combustion of hydrocarbons would qualify, but seems to me that's tiny compared to the existing amount of water, which is all roughly the same age (ancient) and is just continually cycling between vapor (evaporation) and liquid (clouds/rain) state. This discovery is simply water that has been in isolation for a long time.

mtdewcmu 13y ago
True, but once it evaporates, it can no longer be called seawater. I think you may be reading this in the wrong context. It's a geology story, and geologists study things that have been buried in the ground a long time. The value is in having a sample of prehistoric seawater to study, as if it were a rock formation.
mikehotel 13y ago
Recent discoveries of isolated water have lead to investigations of new organisms (see http://www.nature.com/news/russian-scientist-defends-lake-vostok-life-claims-1.12578 http://www.nature.com/news/russian-scientist-defends-lake-vo...). This appears to be much older, but perhaps not as well isolated as Lake Vostok since there appears to be a connection with increased groundwater salinity in the area.

mikehotel 13y ago

Looks like my uneditorialized title was edited to remove the "mind blowing discovery" prefix. I thought HN policy was to use the title as published. In any case, thanks for the edit. I would have done it except for my apparent confusion regarding best practices.

jofer 13y ago

The way this article is written is very misleading. This is not in any form or fashion the "oldest body of seawater yet found" nor is it unusual to find ancient trapped seawater. "Connate water" is water trapped in sediments at the time of their deposition. Whether or not connate water is preserved in large quantities depends on the local permeability structure of the sediments and the regional hydrology. However, it's very common for connate water to be preserved more or less indefinitely (particularly in shales). In other words, there's a _lot_ of trapped seawater almost everywhere you look. What's unique about this isn't that there's trapped seawater, and it's certainly not the oldest connate water discovered (nor do the authors of the actual article claim that it is). It's unique because: A) it's direct evidence that the Central Atlantic had a very high salinity even long after it opened. (The authors are using the term "north atlantic" for some strange reason, but this segment is more commonly referred to as the "central atlantic") B) The connate water survived a metorite impact without being highly disturbed.

imahboob 13y ago

I hate it when these blog journalists don't event know how to read scientific papers

imahboob 13y ago

I hate it when these blog journalists don't event know how to read scientific papers

strathmeyer 13y ago

Mirror??

gt565k 13y ago
right click => inspect element => set style to "display:none" on the popup and overlay, and you're good to go.