Surface-recession weathering of marble tombstones: New field data and constraints

Abstract

Vertical marble-slab tombstones offer unique advantages over natural stone exposures for measuring historical carbonate weathering rates. One of the most commonly measured properties is surface recession rate, defi ned in this study as the difference in thickness between the relatively unweathered base and the weathered top of the tombstone.Use of the "base-minus-top" method makes several assumptions, which are revisited in the light of this research:1. Tombstone thickness from top to base is originally very uniform. Data show that up to 1 mm (but less than 2 mm) original difference in thickness may be common.2. The tombstone base remains suffi ciently unweathered to provide an accurate estimate of the original thickness. Different locations have different maximum ages for which this assumption is valid.3. Weathering is even across the top of the tombstone. Although thickness across the top of an individual weathered tombstone varies, three consistently placed measurements seem to provide a reproducible average thickness.4. Surface recession at the tombstone top is measurable and acceptably precise. The total thickness loss must be signifi cantly greater than the original thickness difference and the experimental error.5. Weathering is dominated by loss of thickness of the marble slab. This assumption is generally correct over long periods of time. However, the data reported here indicate early-stage expansion of some exposed surfaces.6. Surface recession is linear over time. This study documents nonlinear surface recession of tombstone surfaces.

Climate Change Threats to Stone Cultural Heritage: State of the Art of Quantitative Damage Functions and New Challenges for a Sustainable Future

“…Several static and dynamic mathematical models were refined to describe surface changes over time and at any point in time. Many authors tried to assess degradation phenomena by considering changes in surface recession using micrometers [28][29][30] or calipers [27,31]. Other authors tried to assess the effects of environmental parameters (pollutants, rainfall, humidity, temperature, and petrographical features) using climate chamber simulations and defining damage functions [27,[32][33][34][35][36][37][38][39][40][41].…”