Paleotemperatures from fluid inclusions in halite: method verification and a 100,000 year paleotemperature record, Death Valley, CA

Abstract

Maximum homogenization temperatures of fluid inclusions (Th max) in halite (laboratory-grown crystals and modern samples, Death Valley, CA) match maximum brine temperatures during halite precipitation. Maximum brine temperatures during halite precipitation in Death Valley, late April, 1993 (34.4°C) agree with Th max (34°C) and correlate well with average maximum air temperatures in April (31.3°C) and May (37.6°C). Th max may be used for paleoclimate interpretations based on the close relationship between saline lake temperatures and average air temperatures from modern settings. Lower homogenization temperatures, demonstrably below the temperatures at which halite grew, are interpreted to reflect collapse of some fluid inclusion walls due to the pressure difference between the inside and outside of inclusions. By only using Th max, the problems of anomalously low homogenization temperatures due to possible collapse of fluid inclusions are avoided. Halite samples from 30 stratigraphic intervals, 90 to 0 m (100 to 0 ka), Core DV93-1, Death Valley, CA, were used to measure homogenization temperatures of fluid inclusions. Virtually all homogenization temperatures from Core DV93-1 are below the modern Th max of 34°C (halite precipitation late April, 1993). Lacustrine halites, deposited in a perennial saline lake 35 to 10 ka, have Th max between 19°C and 30°C, which suggests brine temperatures approximately 4°C to 15°C below modern late April values. Ephemeral saline lake halites precipitated 60 to 35 ka have Th max between 23°C and 28°C, 6 to 11°C below modern values. The highest Th max value in the 100 ka record (up to 35°C) is from a halite sample formed approximately 100 ka in a climate regime somewhat colder than the modern.