Tannic Water Pockets

[mpen]

A colleague of mine in the UF department of geological sciences who is doing cave research for her phd was asking me yesterday if I've ever seen any tannic/cold water pockets at the bottom of caves. This isn't something I've personally seen, but I figured someone on here has to have seen it before.

Any info when/where you've seen these pockets as well as any pictures of them would be really helpful, particularly interested in Madison and Peacock

My email is [email protected] if you'd rather email

Thanks!

[Trey R]

I've seen tannic pockets in Peacock just before the Chute on the Peanut line. This was last year when the river was up to about 25' at the Luraville gauge.

[MORGAN]

I've seen tannic water pockets in the Wishbone at Peacock on three occasions, always in the farther leg of the circuit. Twice the tannic water was at the top, along the top of the tunnel and filling the domes in the ceiling, with clear water below. Looking up was like looking into a cup of coffee. The other time the tannic water was along the floor with clear water above. My guess was that the first times the tannic water was warmer, and the last time it was colder.

The first time was really cool - a smoky bacteria layer along the bottom, then a layer of clear water, then a layer of tannic above, all separated by very sharp boundaries.

The other place I've seen a tannic pocket was in Peacock off Cisteen, in the little dead end tunnel that goes off to the right (as you're going in) between the Nicholson Tunnel jump and the first Wishbone jump. It's not a marked jump - it goes to the right off a big dome room where the Cisteen Tunnel makes a left hand turn. I don't know what its real name is; Tracy and I call it the Anniversary Tunnel because we dove it for the first time on our wedding anniversary.

Mike

[PfcAJ]

I've seen thick layers of cooler tannic water south of Clearcut Sink in the MM Sink passage, and pockets of it on the ceiling in downstream Promise Sink just before the drop off. There are a few little pockets of tannic water in the passage between the Crypt and Olsen at Peacock that are 'normal'. Sometimes in Peacock III there are layers on the ceiling and in the snaggletoof tunnel.

[jeandiver]

And don't forget the one on the Cross-Over tunnel in Peacock last year. (Ceiling --> Warm)
I don't think I have seen any dark pockets in Madison.

Jean

[Kelly Jessop]

Yes,frequently after flooding events. Well documented with water quality data. We've actually entered these pockets with a hydrolab to record differences of temperature,pH,conductivity,and DO-while performing biota inventories.

[kensuf]

I've heard of one called the "black and tan" tunnel about 10k down in chips hole.

Btw, who is the student? I work in CLAS for the deans office.

[LiteHedded]

Any system with tannic water intrusion will have this. Some get flushed out more quickly than others

[mpen]

Thanks all for the responses. I should have been more specific in the first post but mostly interested in cold/dense, tannic pockets at the bottom of the cave. Wasn't sure if these would actually form or just diffuse downward, but apparently they do!

The other time the tannic water was along the floor with clear water above. My guess was that the first times the tannic water was warmer, and the last time it was colder.

[jason]

Yes,frequently after flooding events. Well documented with water quality data. We've actually entered these pockets with a hydrolab to record differences of temperature,pH,conductivity,and DO-while performing biota inventories.

Does the DO bottom out or does diffusion across the interface result in equalization?