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121-8 Novel Photo-physical Analysis of Speleothems: Lights, Camera, Music?

Session: Caves and Karst Through Space and Time: Biogeochemistry, Climate, and Astrobiology

Presenting Author:

Joshua Sebree

Authors:

Sebree, Joshua¹, Heggen, Jacque², Daughenbaugh, Casey³, Zartman, Catherine⁴, Musgrave, Greta⁵

(1) Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, Iowa, USA, (2) Department of Geological Sciences, The University of Alabama, Tuscaloosa, AL, USA, (3) Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, Iowa, USA, (4) Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, Iowa, USA, (5) Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, Iowa, USA,

Abstract:

The phenomenon of speleothem fluorescence is widely known and has been used to both entertain tourists on cave tours and for scientific purposes both in in situ and in laboratory studies. As speleothems grow, trace impurities (organics and/or metal ions) can become trapped in the crystal matrix giving rise to natural phosphors whose fluorescence emission spectrum can be used to understand the conditions under which some speleothems formed. In addition, air pockets in amorphous crystalline formations have also been postulated to give rise to phosphor type behavior.

Recent discoveries in Wind Cave National Park and Mammoth Cave National Park are leading to the creation of two new methods for the in situ studies of delicate cave formations that cannot be removed from their environments. The Calcite Candlestick in Wind Cave, a hollow, amorphous calcium carbonate formation, has demonstrated the ability to scatter light based on the thickness of the walls of the formation independent of the light’s polarization, potentially creating a way of gaining insights into the internal structure of the formation using Scattering Spectroscopy models.

In Wind Cave and Mammoth Cave (and many other caves in the world), gypsum needles and gypsum beards are a well-known speleothem. Recently, it has been shown that the proper use of lights can be used to induce a photo-acoustic resonance, causing the crystals to “ring” with a pure tone that can be varied with the light source. Photoacoustic Spectroscopy is a well-studied/used technique under a multitude of laboratory conditions but has never been used to understand cave formations and their structure. This new discovery of a photo-acoustic family of speleothems represents a potential new direction for understanding the most delicate cave formations.

Portable Scattering Spectroscopy and Photoacoustic Spectroscopy represent new techniques that can both enhance and go beyond the limits of Fluorescent Spectroscopy while leaving the study environment untouched for future explorers to enjoy and appreciate.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8879

Novel Photo-physical Analysis of Speleothems: Lights, Camera, Music?

Description

Session Format: Oral

Presentation Date: 10/20/2025

Presentation Start Time: 03:45 PM

Presentation Room: HBGCC, 211

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