[Aracelis]

Need someone to do your homework for you? I won't do that but I will give you the following radioisotopic half-lives and their daughter products which are useful in radiometric dating:

• Samarium 147 to Neodynmium 143 - >100,000,000 years
• Rubidium 87 to Strontium 87 - >100,000,000 years
• Thorium 232 to Lead 208 - >200,000,000 years
• Uranium 238 to Lead 206 - >100,000,000 years
• Uranium 235 to Lead 207 - >100,000,000 years
• Potassium 40 to Argon 40 - >100,000 years
• Carbon 14 to Nitrogen 14 - 0 to 80,000 years.

In addition, researchers may use fission track dating, relative time scales, dendrochronology, thermoluminescence, electron-spin resonance, and varve analyses to support and confirm radiometric dating.

Any of these terms may be found on the web.

[Aracelis]

Sorry, those aren't half-lives. The dates reported are useful ranges.

[B.Bumbleberry]

In my armchair studies all authorities have stated that Carbon 14 results become unreliable earlier than about 40,000 years. Your 80,000 year figure therefore is surprising.

[B.Bumbleberry]

And these are not half lives. They are the date rages for which the methods provide reliable results.

[general_re]

In addition, researchers may use fission track dating, relative time scales, dendrochronology, thermoluminescence, electron-spin resonance, and varve analyses to support and confirm radiometric dating.

Indeed - additionally, very interesting work has been done recently with the atom-trap trace analysis technique at Argonne. Very clever method from some clever people ;)