Seafloor manifestations of fluid seepage at the top of a 2000-metre-deep ridge in the eastern Nankai accretionary wedge: Long-lived venting and tectonic implications

Late Miocene seep-carbonates and fluid migration on top of the Montepetra intrabasinal high (Northern Apennines, Italy): Relations with synsedimentary folding

“…Fluid expulsion at the sea floor is evidenced by: 1) specialized seep ecosystems (e.g., Sibuet and Olu, 1998;Van Dover et al, 2003), 2) authigenic carbonates (e.g., Aiello, 2005;Teichert et al, 2005;Campbell et al, 2008), 3) enhanced slope instability (Bohrmann et al, 2002), and 4) mud diapirs and volcanoes (Orange and Breen, 1992;Greinert et al, 2001;Kastner, 2001;Torres et al, 2002;Mazurenko and Soloviev, 2003;Moerz et al, 2005). Fluid emission along active continental margins could be located in erosive structures, such as canyons, head zones and scars of slides and slumpings (Duperret et al, 1995;Von Rad et al, 2000;Majima et al, 2005), or on relatively elevated structures, such as diapir-related mounds and mud volcanoes (Lance et al, 1998;Aloisi et al, 2000;Kopf et al, 2001;Mazurenko et al, 2002;Han et al, 2004), and at the top of anticlines and fault-controlled ridges (Lallemand et al, 1992;Suess et al, 1998Suess et al, , 1999Orphan et al, 2004).…”

Seep faunas and other indicators of methane‐rich dewatering on New Zealand convergent margins

“…Strike-slip faults on the Oregon margin are highly efficient conduits for fluid dewatering from deep level of an accretionary margin (Sample et al 1993;Tobin et al 1993). Those on the upper slope off Japan have permitted fluid flow and the sporadi c growth of crusts and seep faunas for the last 150 000 year-: fluctuation in flow at one seep varying by c. 25% over a 2 week period (Lallemand et al 1992). At many convergent margins, a major change in sedimentary and fault characteristics occurs at the boundary between frontally offscraped (accretionary) wedges and the pre-convergence "backstop" (Cowan & Silling 1978).…”

Sediment instability related to fluid venting in Miocene authigenic carbonate deposits of the northern Apennines (Italy)

“…Stable isotope geochemistry suggests that, in many cases, methane was biogenic in origin, probably derived from the local microbial degradation of turbidite-associated organic matter, but the production rate was probably inadequate for the observed distribution of chemoherms. Concentrated sources of gas or gas-charged fluids migrating along faults are probably required, as convincingly demonstrated by most past and present occurrences of chemoherms, which are consistently associated with fault zones (Ritger et al 1987;Lallemand et al 1992;Kauffman et al 1996;Von Rad et al 1996).…”