Chlorine 36 dating

What does CHLORINE mean?

chlorine 36 dating

Nov 25, Chlorine dating has important potential for archaeology, but recent Chlorine- 36 dates on `bluestones' of Stonehenge have been. Abstract. Chlorine production, principles and experimental method of 36Cl dating are briefly described.1 Chlorine productionChlorine is produced in . A long-lived radioactive isotope of chlorine,, having seventeen protons and nineteen neutrons, and a half-life of 3x10 years; it can be used to date samples of .

Professor Bowen and colleagues have obtained a date of c. However, it is not possible to tell if this is an original exposure date, or if the fragment was brought to Salisbury Plain by iceyears ago or earlier, and was subsequently buried within superficial deposits on Salisbury Plain for part of its history. Or it could have been broken off a larger erratic lying on Salisbury Plain, by natural processes such as frost shattering.

The rock type of this fragment is unknown, and the sample now completely destroyed Professor D. Bowen, in discussion at the meeting of the Lithic Studies Group, Cardiff, 28 Januaryso it may be nothing to do with the bluestone monoliths. Carn Menyn loses material from outcrop surfaces every year through frost shattering.


This will reduce the date obtained on an outcrop. A date of years could represent a preserved quarried surface in which case it might be expected to show quarry marksor it could be a frost-shattered surface. Even if it is a quarried surface, its relevance to Stonehenge is questionable, because the bluestones were erected there about years ago. Thus, even if it is considered that the bluestones were moved by human transport, the Chlorine dates do not tell us at what era that movement might have taken place.

chlorine 36 dating

The article in British Archaeology suggests that dating a monolith surface of a bluestone at Stonehenge will resolve the problem. Unfortunately, it will not.

At least some of the bluestones were dressed and the argument continues about which, and how many were altered in this way. Some have also been damaged by tourists.


When produced at the earth's surface, a muon can react with the nucleus of an atom. When a muon interacts with a calcium or potassium atom both are commonly found in minerals at the earth's surface36Cl can be produced through the following reactions: Finally, 36Cl is produced through thermal neutron absorption.

The 35Cl isotope has a large neutron absorption cross-section, making a relatively large target for collisions with thermal neutrons. The following reaction results in the production of 36Cl from 35Cl in groundwater: To a smaller extent, potassium can absorb neutrons from these same decay reactions and produce 36Cl in the following reaction: This thermonuclear testing produced many tons of neutrons which could readily react with 35Cl to form 36Cl: The neutrons from these earlier tests were mostly absorbed by rock.

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Later tests were conducted on barges in the Pacific Ocean, which were surrounded by a ready supply of 35Cl in seawater. The barge test explosions totaled over 60 megatons and were responsible for most of the stratospheric injection of 36Cl.

chlorine 36 dating

The major fallout occurred between and The 36Cl comes down to the earth as either dry fallout or is cleaned out of the atmosphere by precipitation.