A Review of the Origin and Setting of Tepees and their Associated Fabrics
- Maurice E. Tucker3 and
- Robin G. C. Bathurst4
Published Online: 29 APR 2009
Copyright © 1990 The International Association of Sedimentologists
How to Cite
Kendall, C. G. St. C. and Warren, J. (2009) A Review of the Origin and Setting of Tepees and their Associated Fabrics, in Carbonate Diagenesis (eds M. E. Tucker and R. G. C. Bathurst), Blackwell Publishing Ltd., Oxford, UK. doi: 10.1002/9781444304510.ch2
Department of Geological Sciences, University of Durham, UK
Derwen Deg Fawr, Llanfair DC, Ruthin, Clwyd, North Wales, UK
- Published Online: 29 APR 2009
- Published Print: 21 AUG 1990
Print ISBN: 9780632029389
Online ISBN: 9781444304510
- origin and setting of tepees and their associated fabrics - review;
- carbonate hardgrounds, occurring at shallow subtidal to supratidal, lacustrine, and subaerial carbonate shelf sediments;
- submarine tepees, forming in shallow carbonate-saturated waters;
- lacustrine tepees, forming in margins of shallow salinas;
- tepee structures, as environmental indicators
Carbonate hardgrounds often occur at the surface of shallow subtidal to supratidal, lacustrine, and subaerial carbonate shelf sediments. These are commonly disrupted and brecciated when the surface area of these crusts increases. In the subtidal environment, megapolygons form when cementation of the matrix causes the surface area of the hardgrounds to expand. Similar megapolygons form in the supratidal, lacustrine and subaerial settings when repeated incremental fracturing and fracture fill by sediment and/or cement also causes the area of the hardgrounds to expand. The arched up antiform margins of expansion megapolygons are known as tepees.
The types of tepees found in the geological record include:
(1) Submarine tepees which form in shallow carbonate-saturated waters where fractured and bedded marine grainstones are bound by isopachous marine-phreatic acicular and micritic cements. The surfaces of these brecciated crusts have undergone diagenesis and are bored. Unlike tepees listed below they contain no vadose pisolites or gravity cements;
(2) Peritidal and lacustrine tepees are formed of crusts characterized by fenestral, pisolitic and laminar algal fabrics. This similarity in fabric makes these tepees of different origins difficult to separate.
Peritidal tepees occur where the marine phreatic lens is close to the sediment surface and the climate is tropical. They are associated with fractured and bedded tidal flat carbonates. Their fracture fills contain geopetal asymmetric travertines of marine-vadose origin and/or marine phreatic travertines and/or Terra rossa sediments. The senile form of these peritidal tepees are cut by labyrinthic dissolution cavities filled by the same material.
Lacustrine tepees form in the margins of shallow salinas where periodic groundwater resurgence is common. They include groundwater tepees which form over evaporitic ‘boxwork’ carbonates, and extrusion tepees which also form where periodic groundwater resurgence occurs at the margins of shallow salinas, but the dominant sediment type is carbonate mud. These latter tepee crusts are coated and crosscut by laminated micrite; the laminae extend from the fractures downward into the underlying dolomitic micrite below the crust.
Both peritidal and lacustrine tepees form where crusts experience alternating phreatic and vadose conditions, in time intervals of days to years. Cement morphologies reflect this and the crusts often contain gravitational, meniscus vadose cements as well as phreatic isopachous cement rinds.
(3) Caliche tepees which are developed within soil profiles in a continental setting. They are formed by laminar crusts which contain pisolites, and fractures filled by micritic laminae, microspar, spar and Terra rossa. Most of the cements are gravitational and/or meniscoid.
In ancient carbonates, when their cementation and diagenetic fabric can be interpreted, tepee structures can be used as environmental indicators. They can also be used to trace the evolution of the depositional and hydrological setting.