Stratigraphy The Honda Group unconformably overlies in parts the volcanic deposits of the
Prado Member,
Barzalosa Formation of the
Payandé Group, and in other parts the
Saldaña, and
Santa Teresa Formations. The unit is overlain by the
Neiva Formation of the
Gigante Group. The presence of a hiatus between the Honda Group and the Barzalosa Formation has been suggested. The group is characterised by two main formations; the lower
La Victoria Formation and upper
Villavieja Formation. Previously, the La Dorada Formation has been named as a subdivision of the Honda Group, while other authors define that unit as a member. Other names for members and formations are Cerbatana Member, also published as Cervetana Member, named after Quebrada La Cerbatana, Las Mesitas Formation, El Líbano Formation, Baraya Volcanic Member, named after
Baraya, and Cerro Colorado Red Bed Member. The Perico Member of the La Dorada Formation has been made equivalent to the La Victoria Formation, as well as the El Líbano Formation. consists mainly of
sandstones, conglomeratic sandstones and
conglomerates (75%) with intercalated
claystones and
siltstones (25%).
Villavieja Formation The name Villavieja Formation was first proposed by Wellman in 1968 as a member of the Honda Formation. Two years later, the author elevated the rank to a formation, as part of the Honda Group. The formation takes its name from the
municipality Villavieja, Huila, to the north-northeast of the departmental capital
Neiva. The type locality is situated on the right bank of the
Magdalena River in the
Eastern Ranges of the Colombian Andes. Sediments of the Honda Group restrict the course of the
Sumapaz River to a narrow valley, close to its confluence with the Magdalena River. The majority of the municipality
Prado, Tolima rests upon sediments of the Honda Group. In the Middle Magdalena Basin and the eastern flank of the Central and the western flank of the Eastern Ranges, the group is subdivided into the
Los Limones,
San Antonio and
Cambrás Formations. The total thickness of these formations in the northern original type section of the Honda Group reaches , The age of the Villavieja Formation has been estimated to be between 17.0 and 12.1 Ma, while the stratigraphically lower La Victoria Formation is dated at 13.82 to 12.38 Ma (
Serravallian), based on fission track and volcanic analysis and paleomagnetic research. the lower part of the
León Formation of the
Llanos Basin, the upper range of the
Ciénaga de Oro Formation of the
Lower Magdalena Basin, and the
Caja and
Diablo Formations of the Llanos foothills.
Depositional environment The Honda Group has been deposited in a
fluvial environment, with the lower part of the La Victoria Formation in a meandering setting, while the upper part was formed in a braided river system. The paleocurrent was from the west to the east and east-southeast. The depositional boundary for the Honda Group in the east is formed by the reverse Prado-Suárez and Cambrás-Salinas-Cambao Faults.
Paleoclimate and vegetation Analysis of the "Monkey Beds" of the Honda Group, provided estimates of annual precipitation levels between . Today, these levels of rainfall are associated with the transition between
savanna and forest environments in lowland South America. The vegetation of the La Venta fossil assemblage was diverse due to the different biomes of the depositional environment; meandering and braided river systems in a setting at lower altitudes than the present-day elevation of more than above mean sea level. It has been suggested that the vegetational cover of the Honda Group sedimentary sequence was not a continuous canopy forest, yet a complex pattern of different flora ecosystems. The evergreen Amazonian foothill forests of today would therefore postdate the uplift of the Eastern Ranges of the Andes. Based on vegetational and grazer diversity analysis of the La Venta fauna, it has been suggested the ecosystem resembled more that of Africa and Asia than of the modern Neotropics.
Petroleum geology In the oil-producing Upper Magdalena Basin, the Honda Group is one of the reservoir formations, next to the more important
Caballos and
Monserrate Formations. Shales of the Honda Group function as
seal rock for certain oilfields in the Upper Magdalena Basin. In the
Tello Field in the basin, the Honda Group forms the
overburden rock for the producing Monserrate reservoirs. == Fossil content ==