کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
4466199 1622178 2014 12 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
Cool equatorial terrestrial temperatures and the South Asian monsoon in the Early Eocene: Evidence from the Gurha Mine, Rajasthan, India
ترجمه فارسی عنوان
دمای زمینی استوای گرم و موسیون جنوب آسیا در اوائل ائوسن: شواهد از معدن گوره، راجستان، هند
موضوعات مرتبط
مهندسی و علوم پایه علوم زمین و سیارات فرآیندهای سطح زمین
چکیده انگلیسی


• Early Eocene tropical lake deposits in NW India, yield leaves, fruits and flowers.
• CLAMP analysis gives cooler temperatures than expected for a hothouse climate.
• Growth was year round under humid climate with a clear dry season.
• The South Asian monsoon already existed when India first contacted Asia.
• Changes in monsoon strength occur on timescales too short to be caused by tectonics.

Early Eocene (~ 55–52 Ma) laminated lacustrine sediments overlying lignites in the Gurha Mine (27.87398°N, 72.86709°E), Rajasthan, India, yield a diversity of fossil leaves, flowers, fruits, seeds and insects. CLAMP (multivariate foliar physiognomic) analysis of two horizons separated by an estimated several tens of thousands of years of deposition indicates cool equatorial (~ 10°N) temperatures and a pronounced monsoon signature. A lower assemblage consisting of 54 leaf morphotypes and an upper assemblage of 57 leaf forms yielded mean annual temperatures (MAT) of 24.7 and 23.9 °C, respectively. The uncertainty (± 2.82 °C) means these temperature regimes are identical despite few similarities in the morphotypes between the two assemblages.The mean annual range of temperature (MART) was approximately 9.7 °C for both assemblages. When corrected for evapotranspirational cooling these temperature regimes are similar to those experienced today at 10°N on the west coast of India and surprisingly cool for the tropics at a time of extreme global warmth. Growth was year round. The tropical to paratropical fossil floras also suggest a moist regime (80% annual relative humidity) and high mean annual precipitation of ~ 1800 mm for both assemblages but with a pronounced wet/dry seasonality indicative of a pronounced monsoonal regime. The lower assemblage has a stronger monsoon index (11.8) than the upper assemblage (8.8). The two assemblages seem to have been deposited less than 100 ka apart. This suggests that not only a pronounced South Asian monsoon existed when India and Asia first made contact, but also a variation in monsoon strength existed that cannot be ascribed to tectonic drivers.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Palaeogeography, Palaeoclimatology, Palaeoecology - Volume 412, 15 October 2014, Pages 187–198
نویسندگان
, , , , ,