skip to primary navigationskip to content
 

Nick Evans

Nick Evans

PostDoc

Stable Isotope Geochemistry

Gypsum Hydration Water

Evaporites

M05

Office Phone: +44 (0) 1223 64918

Biography:

 

Future changes to the hydrological cycle are predicted to significantly impact human and natural systems, and extreme climatic events (e.g. droughts and hurricanes) are expected to increase in prevalence. To provide context for future climate changes, it is important to understand climate variability in the past. Understanding the magnitude of past climate variability can be difficult, however, as palaeoclimate indicators for hydrological changes are often qualitative or are convolved with effects from temperature. 

To overcome the limitations of traditional palaeoclimate indicators, recent research has focused on more direct methods to measure hydrological variability in the past. One such method involves the analysis of 'fossil water' that is preserved during the formation of hydrated minerals (where either molecular water or hydroxyl is directly incorporated into the crystalline structure). Studying these hydrated minerals can provide a crucial insight into past climatic changes, and allows us to reconstruct the past history of water on Earth as well as other planetary bodies such as Mars.

Martian Gypsum

 

 

Figure Caption: 

This color view of a mineral vein called "Homestake" comes from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity. The vein is about the width of a thumb and about 18 inches (45 centimeters) long. Opportunity examined it in November 2011 and found it to be rich in calcium and sulfur, possibly the hydrated calcium-sulfate mineral gypsum (CaSO4·2H2O).  

Image Credit: NASA/JPL-Caltech/Cornell/ASU

 

 

Within the Godwin Laboratory, we developed novel methods for the analysis of triple oxygen and hydrogen isotopes in hydrated minerals such as gypsum (CaSO4·2H2O). My work specifically focused on the accurate extraction of mineral hydration water, the calculation of mineral-water isotope fractionation factors, and the application of these methods to constrain hydrologic conditions of past environments:

  • The demise of Lowland Classic Maya civilization during the Terminal Classic Period (~800 to 1000 CE) is a well-cited example of how past climate may have affected ancient societies. Attempts to estimate the magnitude of hydrologic change, however, have met with equivocal success because of the qualitative and indirect nature of available climate proxy data. We provided quantitative palaeoclimate reconstructions from lake sediments in Mesoamerica, and were able to robustly constrain precipitation and relative humidity changes on the Yucatán Peninsula during the Terminal Classic Drought (Evans et al. 2018).

  • During the period known as the Messinian salinity crisis (~5.97-5.33 Ma), the Mediterranean Sea was transformed into a giant brine pool where more than one million cubic kilometers of salt was deposited in 630 ka. The origin of the massive gypsum deposits that formed during this event are still heavily debated. By combining isotopic measurements of gypsum hydration water with traditional (e.g. strontium) and novel (e.g. calcium) isotope tracers and other analytical techniques (e.g. fluid inclusion microthermometry), we have been able to provide a significant advance in our understanding of the evolution of the Messinian Mediterranean Salt Giant (e.g. Evans et al. 2015). Additionally, I have been directly involved with an IODP proposal to drill these deep Mediterranean salt deposits.

  • I have also been involved with the utilisation of other isotope tracers (i.e. strontium, calcium and lithium) to investigate the formation of carbonate veins in the oceanic crust and evaluate their importance in the carbon cycle.

Nevans pulpi Fotor

 

Figure Caption: 

Large to giant gypsum crystals of the Pulpi Geode, Mina Rica near Pilar de Jaravia in Southeastern Spain. 

 

 

 

 

 

 

 

 

 


 

Research Interests

  • Was the Mediterranean a desert? Understanding the Messinian Salinity Crisis 
  • Human-climate-environment interactions - the collapse of the Classic Maya civilization

 

Keywords

Geochemistry ; Stable isotopes

Key Publications

Filed under: