Geology topics

P. Carrara

Publications and source records attributed to P. Carrara.

3 recordsLinked to original sources

USGS2017

Isotopic evidence of Holocene climatic change in the San Juan Mountains, Colorado

The ??D of cellulose from 14C-dated wood, collected in the San Juan Mountains of southwestern Colorado, decreased by about 45??? from 9600 to 3100 yr B.P. and an additional 25??? to the present. The wood samples are from trees that grew above present-day tree line and reflect a time of warmer average summer temperatures. These changes in ??D are interpreted to indicate a major change during the Holocene in the sources of moisture, in the seasonality of precipitation, or in both. ?? 1988.

Quaternary Research↗

USGS2017

Evidence for a former large ice sheet in the Orville Coast- Ronne Ice Shelf area, Antarctica.

The Orville Coast area of the Antarctic Peninsula was extensively glacierized in the past. Striations, polished rock surfaces, and erratics on nunatak summits indicate that this area was covered by a broad regional ice sheet whose grounded ice margin was on the continental shelf, in the present-day Ronne Ice Shelf area. If the glacial history of Antarctica has been controlled by eustatic sea-level changes, the destruction of this ice sheet would have been contemporaneous with that of the Ross Sea ice sheet due to the world-wide rise of eustatic sea-level at the end of the Wisconsin glaciation.

Journal of Glaciology↗

USGS1999

A climatic record from 14C-dated wood fragments from southwestern Colorado

Deuterium concentrations in trees are related to the climatic temperature at which the trees grew. Deuterium analyses were made on all available (39) 14C-dated (all 14C dates cited are uncorrected) wood fragments collected from Lake Emma sediments. The 14C dates range from 9600 to 5400 'B.P.'. Tree line was above Lake Emma at 9600 'B.P.', was at Lake Emma at about 5000 'B.P.', and is 80 m below Lake Emma at the present time. The isotopic records at the various intervals of time coincide very well with this history. The range of ??D values is maximum at 9600 'B.P.' and is minimum at about 5400 'B.P.'. These data allow us to estimate the temperature range for the area between tree line and Lake Emma between these times. These results confirm previously observed cooling trends from several sources in the Western Hemisphere.

Global Biogeochemical Cycles↗