Xixia Amber (Gaogou Formation, 100.5-85.8 Ma)

Amber
Xixia Basin, Xixia County, Henan Province, China
Gaogou Formation (100.5-85.8 Ma)

Total Weight: 10.1 grams

Overview:
This image shows its fluorescence under 365nm longwave UV light. These pieces are all unwashed and still have an extremely fine layer of sediment; each has high clarity and rich color, many are naturally droplet-shaped, and individual measurements range from 1 to 8 millimeters in length. A few fragments of coal are also present within the lot.

Prevalence, Inclusions, Botanical Source:
Amber itself is quite common within the Xixia Basin, hosting China's largest amber reserves, but despite this is very rarely seen on the market. It has also been studied very little, mostly due to the fact that biological inclusions have not been known to occur in it. An araucarian source for this amber was determined based on chemical analysis.

Geological Setting, Associated Fossils, Age:
Amber occurs as lenses and droplets within the middle unit of the Gaogou Fm., in fine-grained sandstone which is non-marine in origin; the middle unit measures up to 440 meters thick, and also contains dinosaur egg and bone fossils, of at least 6 different genera: the presence of some of these species indicate an age of early Late Cretaceous. At other nearby amber sites (Wuliqiao Town) the presence of ostracod and bivalve fossils indicate a slightly younger age (middle to upper Late Cretaceous). Plant and pollen fossils are not known from the amber-bearing strata at Wuliqiao Town.

Given the alluvial setting the amber is found in, and the absence of plant macrofossils in the matrix, I feel it may be possible that the amber was redeposited making it somewhat older than its host strata.

Sources:
"Terpenoid Compositions and Botanical Origins of Late Cretaceous and Miocene Amber from China"; PLoS One, 2014; Shi, Dutta, et al.

"Dinosaur eggs and dinosaur egg-bearing deposits (Upper Cretaceous) of Henan Province, China: Occurrences, palaeoenvironments, taphonomy and preservation"; Progress in Natural Science, 2009; Liang, Wen, et al.