The mineral sphalerite is a witness to the effects of the changing climate on the groundwater. As a testament, these changes in groundwater millions of years ago resulted in the creation of layers of vivid yellow and brown sphalerite.
NOT A COINCIDENCE
In a study published by scientists from Pennsylvania State University, it is explained that these variations within the sphalerite are aligned with the movement of the Earth's orbit that caused the change in the climate.
The study also provided more evidence explaining how climate change influenced rainfall and eventually the groundwater. In a press release provided by the Pennsylvania State University, assistant research professor of geosciences Mingsong Li explains, "this study shows sphalerite banding can be used as a fingerprint of groundwater in the geological past, groundwater is crucial for understanding global sea-level change, chemical weathering and landscape evolution, and this study presents a new idea to help discern the role of groundwater in the Earth system."
She also explains that the increase in precipitation influenced the coloration of the bands in the sphalerite samples that were obtained from the upper Mississippi valley ore mineral district. The study, which was published in the journal Geochemical Perspective Letters, explains that the increase in rainfall leads to oxygen-rich groundwater flowing to depths where these minerals were formed. The increase in oxidation caused yellow bands and the drier times produced the brown ones.
The scientists used a new dating technology and were able to find out that the patterns in the minerals correspond with the changes in Earth's orbit. Professor emeritus Hubert Barnes explains, "What we are doing is marrying geochemical research on ores with what we know about astronomical cycles from very different research. No one has ever made an attempt at this before."
This research drew inspiration from a previous study showing that the hydrothermal fluids created the ore deposits in the states of Iowa, Illinois, and Wisconsin, which started out as groundwater from the Appalachian mountains. However, in this case, there is a high level of rainfall which made groundwater flow 3,000 feet below the surface with higher oxygen levels and it mixed with the hydrothermal fluids and led to the creation of the sphalerite.
IMPORTANCE OF STUDYING GROUNDWATER
According to Mingsong Li, even the slightest changes can have real effects on the sea level. For instance, if all groundwater flows to the sea, the sea level would rise up to 180 feet. "This research opens a new way to evaluate climate control on groundwater activities linked to global water cycles. This is the first direct evidence to show groundwater activities in the deep past," Li concludes.