Burmese amber


Burmese amber, also known as Burmite or Kachin amber, is amber from the Hukawng Valley in northern Myanmar. The amber is dated to around 100 million years ago, during the latest Albian to earliest Cenomanian ages of the mid-Cretaceous period. The amber is of significant palaeontological interest due to the diversity of flora and fauna contained as inclusions, particularly arthropods including insects and arachnids but also birds, lizards, snakes, frogs and fragmentary dinosaur remains. The amber has been known and commercially exploited since the first century AD, and has been known to science since the mid-nineteenth century. Research on the deposit has attracted controversy due to the potential role of the amber trade in funding internal conflict in Myanmar and hazardous working conditions in the mines where it is collected.

Geological context and age

The amber is found in the Hukawng Basin, a large Cretaceous-Cenozoic sedimentary basin within northern Myanmar. The strata have undergone folding and faulting. The Hukawng basin is part of the larger Myanmar Central Basin, a N-S orientated synclinal basin extending to the Gulf of Martaban to the south. The basin is considered to be a part of the West Burma block, which has a debated tectonic history, it is considered to be associated with the concepts of the Cimmeria and Sibumasu terranes. The block was part of Gondwana during at least the Early Paleozoic, but the timing of rifting is very uncertain, with estimates ranging from the Devonian to Early Cretaceous. It is also disputed whether the block had accreted onto the Asian continental margin by the time of the amber deposition. A 2025 study found that the West Burma block had separated from what is now the northwest coast of Australia during the Jurassic period. Paleomagnetic reconstructions by Westerweel et al, have suggested that the Burma terrane formed an island land mass in the Tethys Ocean during the Mid Cretaceous at a latitude around 5-10 degrees south of the equator, considerably northeast of the combined Insular India -Madagascar landmass. Some members of the Burmese amber flora and fauna have Gondwanan affinities, while others have Laurasian affinities.
At Noije Bum, located on a ridge, amber is found within fine grained clastic rocks, typically medium to greyish green in colour, resulting from the constituent grains being black, yellow, grey and light green. The fine grained rocks are primarily fine to very fine grained sandstone, with beds of silt and shale and laterally persistent thin coal horizons. Massive micritic limestone interbeds of 6-8 centimetre thickness, often containing coalified plant material also occur. This facies association is typically around 1 metre thick and typically thinly bedded and laminated. Associated with the fine grained facies is a set of medium facies primarily consisting of medium to fine grained sandstones also containing thin beds of siltstone, shale and conglomerate, alongside a persistent conglomerate horizon. A specimen of the ammonite Mortoniceras has been found in a sandstone bed 2 metres above the amber horizon, alongside indeterminate gastropods and bivalves. Lead-uranium dating of zircon crystals of volcanic clasts within the amber bearing horizons has given a maximum age of 98.79 ± 0.62 million years ago, making the deposit earliest Cenomanian in age. Unpublished data by Wang Bo on other layers suggests an age range of deposition of at least 5 million years. The amber does not appear to have undergone significant transport since hardening or be redeposited. The strata at the site are younging upwards, striking north north-east and dipping 50-70 degrees E and SE north of the ridge and striking between south south-east and south-east and dipping 35-60 degrees south-west south of the ridge, suggesting the site is on the northwest limb of a syncline plunging to the northeast. A minor fault with a conspicuous gouge zone was noted as present, though it appeared to have no significant displacement. Several other localities are known, including the colonial Khanjamaw and the more recent Inzutzut, Angbamo, and Xipiugong sites, within the vicinity of Tanai. The Hkamti site SW of the Hukawng basin has been determined to be significantly older, dating to the early Albian around ca. 110 Ma and is therefore considered distinct.
The amber itself is primarily disc-shaped and flattened along the bedding plane, and is typically reddish brown, with the colour ranging from shades of yellow to red. The opacity of the amber ranges from clear to opaque. Many amber pieces have thin calcite veins that are typically less than, but up to thick. The number and proportion of veins in a piece of amber varies significantly, in some pieces veins are virtually absent, while others are described as being "packed with veinlets".

Paleoenvironment

The Burmese amber paleoforest is considered to have been a tropical rainforest, situated near the coast, where resin was subsequently transported into a shallow marine environment. The shell of a dead juvenile Puzosia ammonite, four marine gastropod shells and littoral or supralittoral isopods entombed in a piece of amber with shell sand, along with growth of Isocrinid crinoids, corals and oysters on the surface of some amber pieces indicate marine conditions for final deposition. Additionally pholadid bivalve borings into amber specimens along with at least one pholadid which became trapped was interpreted to show that the resin was still fresh and unhardened when it was being moved into the tidal areas. However, the phloladids in question, belonging to the extinct genus Palaeolignopholas, were later interpreted as a freshwater species, and the presence of numerous freshwater insects suggests that the initial environment of deposition was a downstream estuarine to freshwater section of a river, with the forests extending across coastal rivers, river deltas, lakes, lagoons, and coastal bays. The forest environment may have been prone to fire, similar to modern tropical peat swamps, based on the presence of fire adapted plants and burned plant remains found in the amber.
The amber is considered to be of coniferous origin, with a likely araucarian source tree, based on spectroscopic analysis and wood fragment inclusions, though a pine origin has also been suggested.

Fauna and flora

The list of taxa is extraordinarily diverse, with 50 classes, 133 orders, 726 families, 1,757 genera and 2,770 species described as of 2023. The vast majority of the species are arthropods, mostly insects.

Arthropods

Over 2500 species of arthropods are known from the deposit, notably including the oldest members of the arachnid orders Palpigradi and Schizomida and the only known fossil members of Ricinulei since the Paleozoic. Chimerarachne is a unique stem-group spider still possessing a tail, with similar forms only known from the Paleozoic, with over 360 other species of spiders being known from Burmese amber, along with over 40 species of scorpions. Other significant arachnid fossils include some of the oldest ticks, as well as the oldest mesostigmatan and opilioacarid mites. Beetles, reflecting their modern diversity, are represented by over 100 families and over 500 species, with Hymenoptera represented by 70 families and 350 species including some of the oldest known ants. Flies are represented by over 50 families and over 250 species and true bugs are represented by over 80 families and over 220 species. Dictyoptera, are represented by over 100 species in 28 families. Odonata, is represented by over 19 families and over 40 species, far higher than in other Cretaceous amber deposits. Among the oldest members of the insect order Zoraptera are known from Burmese amber, as well as the oldest parasitic lice and the oldest members of the parasitic insect order Strepsiptera. The winged insect Aristovia is transitional between the extinct "Grylloblattodea" and modern wingless Grylloblattidae. Over a dozen species each of Myriapoda and Entognatha have also been reported, along with a number of woodlice and various aquatic crustaceans.

Other invertebrates

A wide variety of other invertebrates have been reported. These include gastropods, including freshwater and land snails, the oldest modern onychophoran Cretoperipatus, as well as nematodes, nematomorphs, annelids and flatworms.

Vertebrates

Only a handful of vertebrates have been described from Burmese amber, these include the albanerpetontid Yaksha, the frog Electrorana, a number of primitive toothed birds belonging to the extinct clade Enantiornithes, including the named species Elektorornis and Fortipesavis, the lizards Protodraco '', Cretaceogekko , Electroscincus Barlochersaurus, Oculudentavis, and the snake Xiaophis.'' An indeterminate theropod dinosaur is known from a tail with preserved feathers.

Flora

A wide variety of plants have been reported from the deposit. These include flowering plants, conifers, ferns, lycophytes and bryophytes.

Other

A number of fungi species have been reported, as well as various microorganisms.

History

The amber is recorded as originating from Yunnan Province as early as the first century AD according to the Book of the Later Han. The trade of Burmese amber into China during the Han Dynasty has been confirmed by Fourier-transform infrared spectroscopy analysis of amber artifacts from the Eastern Han Dynasty. It was first mentioned in European sources by the Jesuit Priest Álvaro Semedo who visited China in 1613, it was described as being "digged out of mines, and sometimes in great pieces, it is redder than our amber though not so cleane". The locality itself has been known to European explorers since the 1800s with visitation to the Hukawng Valley by Simon Fraser Hannay in 1836–1837. At that time the principle products of the valley mines were salt, gold, and amber, with the majority of gold and amber being bought by Chinese traders. Hannay visited the amber mines themselves on March 21, 1836, and he noted that the last three miles to the mines were marked with numerous abandoned pits, up to in depth, where amber had been dug in the past. The mining had moved over the hill to a series of 10 pits but no visible amber was seen, suggesting that miners possibly hid the amber found that day before the party arrived. Mining was being performed manually at the time through the use of sharpened bamboo rods and small wooden shovels. Finer pieces of amber were recovered from the deeper pits, with clear yellow being recovered from depths of The recovered amber was bought with silver or often exchanged for jackets, hats, copper pots, or opium among other goods. Mixed and lower quality amber was sold from around ticals to 4 rupees per seer. Pieces that were considered high quality or fit for use as ornamentation were described as expensive, and price varied depending on the clarity and color of the amber. Women of the valley were noted to wear amber earrings as part of their jewelry. In 1885 the Konbaung dynasty was annexed to the British Raj and a survey of the area was conducted by Dr. Fritz Noetling on behalf of the Geological Survey of India. The final research before Burmese independence in 1947 was conducted by Dr. H.L. Chhibber in 1934, who provided the most detailed description of Burmite occurrences.