Effects of finite rifting times on the development of sedimentary basins

Abstract

Most thermo-mechanical models for the development of sedimentary basins have assumed that the rifting responsible for the formation of the basin occurred instantaneously and have examined the post-rift development of the basin. This assumption greatly simplifies the mathematical treatment, but is not in accord with what is found in nature, where 10to 50-m.y. rifting events commonly accompany the formation of sedimentary basins and continental margins. The effects of a finite rifting time on the development of sedimentary basins are examined using an analytic technique which allows an arbitrary rifting history in both time and space and which considers the effects of both vertical and horizontal heat transfer. This technique allows the thermal structure of the lithosphere to be calculated throughout the rifting event and thus permits the subsidence history and surface heat flow of the developing basin to be traced.The effect of a finite-duration extension event is that heat is lost during rifting increasing the syn-rift subsidence at the expense of the post-rift. Lateral heat flow, which was not included in previous studies of the effect of finite rifting times, has a significant effect on the subsidence history, distribution of sediments and thermal history. In particular, the post-rift subsidence is decreased by more than 25% for a 20-m.y. rifting event and by more than 10-15% for a rifting event as short as 10 m.y. This will significantly decrease the subsidence rates in the post-rift stage and implies that inferences concerning the structure, development and thermal history of the basin derived from using "fl-curves" to interpret backstripped subsidence can be greatly in error.Variations in syn-rift sediment accumulation and lithospheric thermal structure at the end of rifting resulting from different rifting histories can interact with other factors, such as the flexural response of the lithosphere to sediment loading, to affect the final width of the basin, the total amount of sediments that accumulate and the basin stratigraphy.Lamont-Doherty Geological Observatory Contribution No. 3518.

Transform margins: development, controls and petroleum systems – an introduction

“…(1) depth-dependent extension (Royden & Keen 1980;Hellinger & Sclater 1983;Watts & Thorne 1984;Morgan et al 1985); (2) lateral heat flow (Steckler 1981;Cochran 1983;Alvarez et al 1984;Buck et al 1988); and (3) secondary convection under rift shoulders (Keen 1985;Steckler 1985;Buck 1986). In addition, representing permanent uplift mechanisms, they are driven by: (1) magmatic underplating (Cox 1980;Ewart et al 1980;McKenzie 1984;White & McKenzie 1988); (2) flexural-isostatic uplift (Watts et al 1982;Gilchrist & Summerfield 1990;Weissel & Karner 1994); and (3) lithospheric unloading and/or ductile necking (Zuber & Parmentier 1986;Parmentier 1987;Braun & Beaumont 1989;Issler et al 1989;Chery et al 1992;Weissel & Karner 1994), Further contribution comes from: (1) the erosional unloading of margin coupled with depositional loading of basin (e.g.…”

Uplift, denudation, and their causes and constraints over geological timescales

“…This appears to have been the case in Eastern Australia during the late Cretaceous, where prolonged subsidence of the continental interior abruptly ceased, and was succeeded by denudation (Gallagher et al 1994), Transient thermal uplift can also occur at rift margins, as a consequence of the rifting process itself. The introduction of relatively hot mantle in the rift zone against colder mantle/crust in the rift margins leads to lateral heat transfer from the former to the latter (Cochran 1983). This reduces the mean density of the unrifted region, and through isostasy, there will be surface uplift.…”

Heat flow and tectonics of the Ligurian Sea basin and margins

“…Due to the unresolved nature of the magnetic anomalies, more confidence may be placed on tectonic models derived from heat flow. Furthermore, the corrected heat flow in the central Ligurian Basin is too high according to theoretical two-dimensional studies of basin formation (Cochran, 1983;Alvarez et al, 1984), so that the effect of lateral heat loss in narrow basins may be over-estimated. Possible factors which may enhance one-dimensional cooling are a regionally thin prerift lithosphere and significant anisotropy-for the upper mantle thermal conductivity.…”

“…Surface heat flow is further modified by horizontal conduction of heat from extended crust to the relatively cooler less extended continental block (Alvarez et al, 1984;Cochran, 1983;Steckler and Watts, 1980) and the effects of a prolonged duration of rifting (Cochran, 1983;Jarvis and McKenzie, 1980). Tectonic interpretation of heat flow measurements on the thin oceanic-type crust of the central Ligurian Basin reduces to a simpler problem since the total radiogenic heat contribution is small.…”