ier ▁between ▁Brazil ▁and ▁Guy ana . ▁Ir eng ' s ▁main ▁trib ut aries ▁are ▁the ▁U ail an ▁and ▁Can ã ▁rivers ▁on ▁the ▁Brazil ian ▁side ▁and ▁the ▁C ac ó , ▁D ac ã ▁and ▁Soc obi ▁rivers ▁on ▁the ▁Gu yan ese ▁side . ▁All ▁of ▁these ▁rivers ▁merge ▁with ▁the ▁upper ▁and ▁middle ▁sections ▁of ▁the ▁Ir eng . ▁Their ▁courses ▁are ▁through ▁bre at ht aking ▁form ations ▁of ▁sed iment ary ▁rocks ▁formed ▁by ▁t ect onic ▁movements ▁in ▁ancient ▁times . ▁The ▁Ir eng ▁River ' s ▁waters ▁are ▁dark , ▁bearing ▁a ▁striking ▁res embl ance ▁to ▁that ▁of ▁Rio ▁Neg ro ▁near ▁Man aus , ▁in ▁Brazil ian ▁state ▁of ▁Amazon as . ▁ ▁It ▁is ▁considered ▁to ▁be ▁the ▁most ▁pictures que ▁of ▁Guy ana ' s ▁many ▁rivers . ▁Or indu ik ▁F alls ▁and ▁Tak ag ka ▁F alls ▁are ▁located ▁on ▁the ▁Ir eng ▁River . ▁ ▁B iod iversity ▁in ▁the ▁Ir eng ▁The ▁Ir eng ▁River ▁region ▁is ▁home ▁to ▁such ▁re pt ile ▁species ▁as ▁the ▁Ant illes ▁leaf - to ed ▁ge cko ▁( H em id act yl us ▁p ala ich th us ) ▁and ▁rain bow ▁wh ipt ail ▁( C nem id op hor us ▁lem nis c atus ); ▁am ph ib ians ▁such ▁as ▁the ▁sap o ▁dor ado ▁( B uf o ▁g utt atus ) ▁and ▁Le pt od act yl us ▁bol iv ian us