History of Myanmar

7/25/2019 History of Myanmar

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Introduction

The geological history of Myanmar is summarized in a sequential order in 39 stages. The

approach is mainly descriptive and only partly interpretative. The plate tectonic reconstruction

are kept to a bare minimum partly because these are more or less conjectural particularly for the

!recambrian and !aleozoic eras" and partly because the descriptive geological events are

considered to be more interesting than the paleo#plate movements and past $hereabouts of the

Myanmar region. %our stages in the paleogeographic evolution are sho$n in a diagram. &

graphic summary of the main geological events and a simplified geological map of Myanmar are

also appended.

'equence of Major (vents

)uring the !recambrian and !aleozoic eras* !roto#Myanmar region $as a part of 'inoburmalaya

that probably $as a fragment of northern +ond$analand in 'outhern ,emisphere. This linear

block $as roughly aligned -#'(.

/ate !recambrian

0. (1istence of a crystalline basement in northeastern !roto#Myanmar (astern 2achin

Metamorphics" that e1tended north$ards into !roto#unan* and probably southeast$ards

into the Mogok +neiss.4. /ater* deposition of very thick 5haung Magyi sediments under deep sea conditions in

!roto#'han region.

3. 6rogeny at the end of !recambian causing fairly intense deformation* lo$#grade regionalmetamorphism* and uplift7 thus* a part of northeastern !roto#Myanmar first became land.

(arly !aleozoic

The !aleo#Tethys oceanic plate probably moved from -( to ' and subducted belo$

'inoburmalaya. 'hallo$ marine sediments $ere deposited in an apparently passive continental

margin of 'inoburmalaya.

8. )eposition of -g$etaung and !angyun sandstones and Molohein sandstones in the

northern and southern parts of !roto#'han region* respectively* on a stable sheft during

/ate 5ambrian eruption of the :a$d$in volcanics $ith associated volcanogenic massive

sulphide ;M'" lead#zinc#silver deposit in the same period.


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=. 5ontinuous depositional of 'ilurian phacoidal limestones and clastics* locally $ith some

tuff and ash beds in southern !roto#'han region7 deposition of Mergui sediments

probably began during 'ilurian in !roto#Tanintharyi region

)evonian

>. 5ontinuous sedimentation from 'ilurian to )evonian in some parts of !roto#'han region

as black limestone* black shale and reefal limestone $ere deposited at thin units of

limited distribution under lagoonal and restricted marine conditions.

?. )eposition of a limestone unit later dolomitized into Maymyo )olomite" began in !roto#

'han region* especially in the northern part. That deposition continued into

5arboniferous.9. )eposition of Mergui sediments continued in !roto#Tanintharyi region.

(arly 5arboniferous

'eparation of 'inoburmalaya from +ond$analand* and its initial movement

northeast$ards in the !aleo#Tethys in 5arboniferous times.

0@. 5ontinued deposition of Mergui sediments* locally $ith tuff and agglomerate beds* under

deep#sea conditions in !roto#Tanintharyi#Mon region. The depositional site e1tended

north$est$ards into the $estern marginal part of southern !roto#'han region $here

/ebyin clastics $ere deposited"00. 6rogeny at the end of (arly 5arboniferous resulting in the deformation and lo$#grade

regional metamorphism of Mergui +roup* and possibly the intrusion of some graniteplutons in !roto#'han region Ae.g.* Taung#baing +ranite". The fairly $idespread small#

scale antimony mineralization in the /ebyin and Taungnyo clastics e.g.* at /ebyin and

-atsan mines" $as possibly related to this igneous activity.

/ate 5arboniferous#Middle Triassic

04. )eposition of a thick limestone sequence !lateau /imestone* Moulmein /imestone* and

2ama$kala /imestone"* later partially dolomitized* in a $ide $arm shallo$ sea that

covered most of !roto#'han#2ayah#2ayin region. This $ide carbonate platform

e1tended into !roto#unnan in the north$est* and into !roto#estern Thailand in theeast". & thin clastic $edge $as also deposited in some parts of !roto#Mon#2ayah region

during /ate !ermian.

03. (arth movements* intrusion of granited in eastern !roto#'han region* and initial

emergence of !roto#'han#Tanintharyi region at the end of Middle Triassic.

Middle#/ate Triassic


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5ontinued northeast$ard movement of 'inoburmalaya in the -eo#Tethys. 'outh$est of

the emerging land lay a deep sea in $hich flysch beds $ere laid do$n. The northeast$ard#

moving ocean floor then began to subduct belo$ the emerging !roto#'han#Tanintharyi landmass.

08. )epositional of a thick deep#sea flysch unit containing fossils ofHalobiaandDaonella

and locally ophiolites Thanbaya %ormation" along the northeastern margin of !roto#Bakhine#5hin region.

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43. In contrast* during /ate 5retaceous#(arly !aleocene* intrusion of small and medium#

sized ultramafic bodies along the eastern flank of !roto#Bakhine#-aga region

'erpentinite /ine" and in !roto#2achin region* $ith associated nickel#chromium

mineralization in northern !roto#5hin ,ills notably at M$e#taung" and jadeite

mineralization in $estern !roto#2hanti and !roto#Ta$ma$ areas.

48. :eginning of igneous activity in the northern part of 5entral Igneous /ine i.e.* in !roto#

untho area" at the close of 5retaceous.

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%urther rotational $est$ard movement of southeast &sian !eninsula* and by (arly

Miocene it nearly reached its present position.

34. 'ubduction#related volcanism along 5entral Igneous /ine during Miocene formed a

volcanic arc that became a substantial barrier separating the graben into t$o troughs in

$hich thick Miocene sediments Epper !egu +roup" $ere laid do$n separately as t$ofairly different sequences. 5oncurrently* molassic sediments $ere also being laid do$n in

the northern part of the Bakhine 5oastal :eltDthe southern e1tension of &ssan :asin in

northeast India.

33. -orth$ard movement of the oceanic crust from a spreading center in the &ndaman 'ea

since Middle Miocene* resulting in the development of F:urma !lateGDa microplate

bounded on the east by the 'againg %ault and on the $est by the &ndaman Thrust.

38. /ate phase of ,imalayan orogeny during /ate Miocene* resulting in the folding and uplift

of 5entral :elt* particularly the :ago omas7 oil and natural gas migrated and

accumulated in the folded (ocene and !egu sandstones along the eastern side of Minbu

:asin e.g.* at 5hauk* Mann* /etpando"7 intrusion of younger granites mainlymicrogranite* e.g.* 2abaing +ranite" along the Mogok :elt.

!liocene

3. )eposition of Eyu boulder conglomerates* plateau gravels* and river terraces along big

river valleys in northern 5entral :elt during !leistocene.

3?. Bene$ed volcanism mainly andesites and basalts" along 5entral Igneous /ine* e.g.* at

Mt. !opa and T$indaung* during !leistocene and (arly ,olocene.

39.)epositions of ne$er alluvium and denudation have been going on side by side since the

beginning of ,olocene to form the present the present landscape of Myanmar.

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History of Myanmar